cleaning code

android/app/src/main/java/com/example/petstoremobile/fragments/ChatFragment.java

@@ -214,9 +214,11 @@ public class ChatFragment extends Fragment implements ChatAdapter.OnChatClickLis
             Toast.makeText(requireContext(), "Downloading " + message.getAttachmentName() + "...", Toast.LENGTH_SHORT).show();
 
             viewModel.downloadAttachment(message.getId()).observe(getViewLifecycleOwner(), resource -> {
-                if (resource != null && resource.status == Resource.Status.SUCCESS && resource.data != null) {
+                if (resource == null) return;
+                setLoading(resource.status == Resource.Status.LOADING);
+                if (resource.status == Resource.Status.SUCCESS && resource.data != null) {
                     saveFileToDownloads(resource.data, message.getAttachmentName(), message.getAttachmentMimeType());
-                } else if (resource != null && resource.status == Resource.Status.ERROR) {
+                } else if (resource.status == Resource.Status.ERROR) {
                     Toast.makeText(requireContext(), "Download failed: " + resource.message, Toast.LENGTH_SHORT).show();
                 }
             });
@@ -285,9 +287,13 @@ public class ChatFragment extends Fragment implements ChatAdapter.OnChatClickLis
             scrollToBottom();
         });
 
-        viewModel.getIsLoading().observe(getViewLifecycleOwner(), loading -> {
+        viewModel.getIsLoading().observe(getViewLifecycleOwner(), this::setLoading);
-            // Can show a progress bar if needed
+    }
-        });
+
+    private void setLoading(boolean loading) {
+        if (binding != null && binding.progressBar != null) {
+            binding.progressBar.setVisibility(loading ? View.VISIBLE : View.GONE);
+        }
     }
 
     private void updateTitleAndStateIfActive(List<Chat> list) {
@@ -324,15 +330,12 @@ public class ChatFragment extends Fragment implements ChatAdapter.OnChatClickLis
             activeConversationId = getActivity().getIntent().getLongExtra("conversation_id", -1);
             getActivity().getIntent().removeExtra("conversation_id");
         } else {
-            // Restore last active conversation if any
             activeConversationId = viewModel.getLastActiveConversationId();
         }
 
         viewModel.loadCustomers();
 
-        //
         if (activeConversationId != null) {
-            // Re-subscribe and load history if there is an active conversation ID
             if (stompChatManager != null) stompChatManager.subscribeToConversation(activeConversationId);
             viewModel.loadMessageHistory(activeConversationId);
         } else {
@@ -360,7 +363,9 @@ public class ChatFragment extends Fragment implements ChatAdapter.OnChatClickLis
 
         binding.etMessage.setText("");
         viewModel.sendMessage(activeConversationId, text).observe(getViewLifecycleOwner(), resource -> {
-            if (resource != null && resource.status == Resource.Status.SUCCESS && resource.data != null) {
+            if (resource == null) return;
+            setLoading(resource.status == Resource.Status.LOADING);
+            if (resource.status == Resource.Status.SUCCESS && resource.data != null) {
                 viewModel.addMessageLocally(resource.data);
                 viewModel.loadConversations();
             }
@@ -416,10 +421,12 @@ public class ChatFragment extends Fragment implements ChatAdapter.OnChatClickLis
         removeAttachment();
 
         viewModel.sendMessageWithAttachment(activeConversationId, contentPart, filePart).observe(getViewLifecycleOwner(), resource -> {
-            if (resource != null && resource.status == Resource.Status.SUCCESS && resource.data != null) {
+            if (resource == null) return;
+            setLoading(resource.status == Resource.Status.LOADING);
+            if (resource.status == Resource.Status.SUCCESS && resource.data != null) {
                 viewModel.addMessageLocally(resource.data);
                 viewModel.loadConversations();
-            } else if (resource != null && resource.status == Resource.Status.ERROR) {
+            } else if (resource.status == Resource.Status.ERROR) {
                 Toast.makeText(requireContext(), "Failed to send attachment: " + resource.message, Toast.LENGTH_SHORT).show();
             }
         });

android/app/src/main/java/com/example/petstoremobile/fragments/ProfileFragment.java

@@ -172,6 +172,12 @@ public class ProfileFragment extends Fragment {
         return binding.getRoot();
     }
 
+    private void setLoading(boolean loading) {
+        if (binding != null && binding.progressBar != null) {
+            binding.progressBar.setVisibility(loading ? View.VISIBLE : View.GONE);
+        }
+    }
+
     @Override
     public void onDestroyView() {
         super.onDestroyView();
@@ -184,6 +190,7 @@ public class ProfileFragment extends Fragment {
     private void loadProfileData() {
         viewModel.getMe().observe(getViewLifecycleOwner(), resource -> {
             if (resource == null) return;
+            setLoading(resource.status == Resource.Status.LOADING);
             if (resource.status == Resource.Status.SUCCESS && resource.data != null) {
                 currentUser = resource.data;
 
@@ -229,6 +236,7 @@ public class ProfileFragment extends Fragment {
             //Call the backend to upload the avatar
             viewModel.uploadAvatar(body).observe(getViewLifecycleOwner(), resource -> {
                 if (resource == null) return;
+                setLoading(resource.status == Resource.Status.LOADING);
                 if (resource.status == Resource.Status.SUCCESS) {
                     Toast.makeText(getContext(), "Avatar updated successfully", Toast.LENGTH_SHORT).show();
                     loadProfileData();
@@ -247,6 +255,7 @@ public class ProfileFragment extends Fragment {
     private void deleteAvatar() {
         viewModel.deleteAvatar().observe(getViewLifecycleOwner(), resource -> {
             if (resource == null) return;
+            setLoading(resource.status == Resource.Status.LOADING);
             if (resource.status == Resource.Status.SUCCESS) {
                 hasImage = false;
                 binding.imgProfile.setImageResource(R.drawable.placeholder);
@@ -266,6 +275,7 @@ public class ProfileFragment extends Fragment {
 
         viewModel.updateMe(updates).observe(getViewLifecycleOwner(), resource -> {
             if (resource == null) return;
+            setLoading(resource.status == Resource.Status.LOADING);
             if (resource.status == Resource.Status.SUCCESS && resource.data != null) {
                 currentUser = resource.data;
                 Toast.makeText(getContext(), "Profile updated successfully", Toast.LENGTH_SHORT).show();

android/app/src/main/java/com/example/petstoremobile/fragments/listfragments/AnalyticsFragment.java

@@ -41,6 +41,7 @@ public class AnalyticsFragment extends Fragment {
         viewModel.getAnalyticsData().observe(getViewLifecycleOwner(), this::computeAndDisplay);
         
         viewModel.getIsLoading().observe(getViewLifecycleOwner(), loading -> {
+            binding.progressBar.setVisibility(loading ? View.VISIBLE : View.GONE);
             if (loading) {
                 binding.tvTotalRevenue.setText("Loading...");
                 binding.tvTotalTransactions.setText("...");
@@ -117,8 +118,6 @@ public class AnalyticsFragment extends Fragment {
         if (data.employeePerformance != null && !data.employeePerformance.isEmpty()) {
             BigDecimal maxEmp = data.employeePerformance.get(data.employeePerformance.size() - 1).getValue();
             if (maxEmp.compareTo(BigDecimal.ZERO) == 0) maxEmp = BigDecimal.ONE;
-            // Sorting is ascending from VM for some reason? Let's check VM... it says b.getValue().compareTo(a.getValue()) which is DESC.
-            // Wait, computeAnalytics sorts them... let's assume DESC as per VM code.
             maxEmp = data.employeePerformance.get(0).getValue();
             if (maxEmp.compareTo(BigDecimal.ZERO) == 0) maxEmp = BigDecimal.ONE;
 

android/app/src/main/java/com/example/petstoremobile/fragments/listfragments/detailfragments/AdoptionDetailFragment.java

@@ -1,6 +1,5 @@
 package com.example.petstoremobile.fragments.listfragments.detailfragments;
 
-import android.app.DatePickerDialog;
 import android.os.Bundle;
 import android.view.*;
 import android.widget.*;
@@ -12,7 +11,9 @@ import androidx.navigation.fragment.NavHostFragment;
 
 import com.example.petstoremobile.databinding.FragmentAdoptionDetailBinding;
 import com.example.petstoremobile.dtos.*;
+import com.example.petstoremobile.utils.DateTimeUtils;
 import com.example.petstoremobile.utils.DialogUtils;
+import com.example.petstoremobile.utils.InputValidator;
 import com.example.petstoremobile.utils.Resource;
 import com.example.petstoremobile.utils.SpinnerUtils;
 import com.example.petstoremobile.utils.UIUtils;
@@ -73,6 +74,12 @@ public class AdoptionDetailFragment extends Fragment {
         viewModel.getEmployeeList().observe(getViewLifecycleOwner(), list -> refreshEmployeeSpinner());
     }
 
+    private void setLoading(boolean loading) {
+        if (binding != null && binding.progressBar != null) {
+            binding.progressBar.setVisibility(loading ? View.VISIBLE : View.GONE);
+        }
+    }
+
     @Override
     public void onDestroyView() {
         super.onDestroyView();
@@ -116,29 +123,27 @@ public class AdoptionDetailFragment extends Fragment {
     }
 
     private void setupDatePicker() {
-        binding.etAdoptionDate.setOnClickListener(v -> {
+        binding.etAdoptionDate.setOnClickListener(v -> UIUtils.showDatePicker(requireContext(), binding.etAdoptionDate, null));
-            Calendar c = Calendar.getInstance();
-            new DatePickerDialog(requireContext(),
-                    (dp, y, m, d) -> binding.etAdoptionDate.setText(
-                            String.format("%04d-%02d-%02d", y, m + 1, d)),
-                    c.get(Calendar.YEAR),
-                    c.get(Calendar.MONTH),
-                    c.get(Calendar.DAY_OF_MONTH)).show();
-        });
     }
 
     private void loadSpinnersData() {
         viewModel.loadPets().observe(getViewLifecycleOwner(), resource -> {
+            if (resource == null) return;
+            setLoading(resource.status == Resource.Status.LOADING);
             if (resource.status == Resource.Status.SUCCESS && resource.data != null) {
                 viewModel.setPetList(resource.data);
             }
         });
         viewModel.loadCustomers().observe(getViewLifecycleOwner(), resource -> {
+            if (resource == null) return;
+            setLoading(resource.status == Resource.Status.LOADING);
             if (resource.status == Resource.Status.SUCCESS && resource.data != null) {
                 viewModel.setCustomerList(resource.data);
             }
         });
         viewModel.loadStores().observe(getViewLifecycleOwner(), resource -> {
+            if (resource == null) return;
+            setLoading(resource.status == Resource.Status.LOADING);
             if (resource.status == Resource.Status.SUCCESS && resource.data != null) {
                 viewModel.setStoreList(resource.data);
             }
@@ -165,7 +170,9 @@ public class AdoptionDetailFragment extends Fragment {
 
     private void loadEmployees(Long storeId) {
         viewModel.loadEmployees(storeId).observe(getViewLifecycleOwner(), resource -> {
-            if (resource != null && resource.status == Resource.Status.SUCCESS && resource.data != null) {
+            if (resource == null) return;
+            setLoading(resource.status == Resource.Status.LOADING);
+            if (resource.status == Resource.Status.SUCCESS && resource.data != null) {
                 viewModel.setEmployeeList(resource.data);
             }
         });
@@ -183,7 +190,7 @@ public class AdoptionDetailFragment extends Fragment {
             long adoptionId = a.getLong("adoptionId");
             viewModel.setAdoptionId(adoptionId);
             binding.tvAdoptionMode.setText("Edit Adoption");
-            binding.tvAdoptionId.setText("ID: " + adoptionId);
+            binding.tvAdoptionId.setText(DateTimeUtils.formatId(adoptionId));
             binding.tvAdoptionId.setVisibility(View.VISIBLE);
             binding.btnDeleteAdoption.setVisibility(View.VISIBLE);
             loadAdoptionData();
@@ -199,6 +206,7 @@ public class AdoptionDetailFragment extends Fragment {
     private void loadAdoptionData() {
         viewModel.loadAdoption().observe(getViewLifecycleOwner(), resource -> {
             if (resource == null) return;
+            setLoading(resource.status == Resource.Status.LOADING);
             if (resource.status == Resource.Status.SUCCESS && resource.data != null) {
                 AdoptionDTO a = resource.data;
                 preselectedPetId = a.getPetId() != null ? a.getPetId() : -1;
@@ -224,29 +232,16 @@ public class AdoptionDetailFragment extends Fragment {
     }
 
     private void saveAdoption() {
-        if (binding.spinnerAdoptionCustomer.getSelectedItemPosition() == 0) {
+        if (!InputValidator.isSpinnerSelected(binding.spinnerAdoptionCustomer, "Customer")) return;
-            Toast.makeText(getContext(), "Select a customer", Toast.LENGTH_SHORT).show(); return;
+        if (!InputValidator.isSpinnerSelected(binding.spinnerAdoptionPet, "Pet")) return;
-        }
+        if (!InputValidator.isSpinnerSelected(binding.spinnerAdoptionStore, "Store")) return;
-        if (binding.spinnerAdoptionPet.getSelectedItemPosition() == 0) {
+        if (!InputValidator.isNotEmpty(binding.etAdoptionDate, "Adoption Date")) return;
-            Toast.makeText(getContext(), "Select a pet", Toast.LENGTH_SHORT).show(); return;
-        }
-        if (binding.spinnerAdoptionStore.getSelectedItemPosition() == 0) {
-            Toast.makeText(getContext(), "Select a store", Toast.LENGTH_SHORT).show(); return;
-        }
-        String date = binding.etAdoptionDate.getText().toString().trim();
-        if (date.isEmpty()) {
-            Toast.makeText(getContext(), "Select a date", Toast.LENGTH_SHORT).show(); return;
-        }
 
         BigDecimal fee = BigDecimal.ZERO;
         String feeStr = binding.etAdoptionFee.getText().toString().trim();
         if (!feeStr.isEmpty()) {
-            try {
+            if (!InputValidator.isPositiveDecimal(binding.etAdoptionFee, "Adoption Fee")) return;
             fee = new BigDecimal(feeStr);
-            } catch (NumberFormatException e) {
-                Toast.makeText(getContext(), "Invalid fee format", Toast.LENGTH_SHORT).show();
-                return;
-            }
         }
 
         DropdownDTO customer = viewModel.getCustomerList().getValue().get(binding.spinnerAdoptionCustomer.getSelectedItemPosition() - 1);
@@ -258,6 +253,7 @@ public class AdoptionDetailFragment extends Fragment {
             employeeId = viewModel.getEmployeeList().getValue().get(binding.spinnerAdoptionEmployee.getSelectedItemPosition() - 1).getId();
         }
         
+        String adoptionDate  = binding.etAdoptionDate.getText().toString().trim();
         String status        = STATUSES[binding.spinnerAdoptionStatus.getSelectedItemPosition()];
 
         AdoptionDTO dto = new AdoptionDTO(
@@ -265,12 +261,14 @@ public class AdoptionDetailFragment extends Fragment {
                 customer.getId(),
                 employeeId,
                 store.getId(),
-                date,
+                adoptionDate,
                 status,
                 fee
         );
 
         viewModel.saveAdoption(dto).observe(getViewLifecycleOwner(), resource -> {
+            if (resource == null) return;
+            setLoading(resource.status == Resource.Status.LOADING);
             if (resource.status == Resource.Status.SUCCESS) {
                 Toast.makeText(getContext(), viewModel.isEditing() ? "Updated" : "Saved", Toast.LENGTH_SHORT).show();
                 navigateBack();
@@ -281,8 +279,10 @@ public class AdoptionDetailFragment extends Fragment {
     }
 
     private void confirmDelete() {
-        DialogUtils.showDeleteConfirmDialog(requireContext(), "Adoption", () ->
+        DialogUtils.showDeleteConfirmDialog(requireContext(), "Adoption Record", () ->
                 viewModel.deleteAdoption().observe(getViewLifecycleOwner(), resource -> {
+                    if (resource == null) return;
+                    setLoading(resource.status == Resource.Status.LOADING);
                     if (resource.status == Resource.Status.SUCCESS) {
                         Toast.makeText(getContext(), "Deleted", Toast.LENGTH_SHORT).show();
                         navigateBack();

android/app/src/main/java/com/example/petstoremobile/fragments/listfragments/detailfragments/AppointmentDetailFragment.java

@@ -19,6 +19,7 @@ import com.example.petstoremobile.dtos.DropdownDTO;
 import com.example.petstoremobile.dtos.ServiceDTO;
 import com.example.petstoremobile.utils.DateTimeUtils;
 import com.example.petstoremobile.utils.DialogUtils;
+import com.example.petstoremobile.utils.InputValidator;
 import com.example.petstoremobile.utils.Resource;
 import com.example.petstoremobile.utils.SpinnerUtils;
 import com.example.petstoremobile.utils.UIUtils;
@@ -140,6 +141,12 @@ public class AppointmentDetailFragment extends Fragment {
             SpinnerUtils.populateSpinner(requireContext(), binding.spinnerStaff, list, DropdownDTO::getLabel, "-- Select Staff --", preselectedStaffId, DropdownDTO::getId));
     }
 
+    private void setLoading(boolean loading) {
+        if (binding != null && binding.progressBar != null) {
+            binding.progressBar.setVisibility(loading ? View.VISIBLE : View.GONE);
+        }
+    }
+
     private void applyViewState(AppointmentDetailViewModel.ViewState state) {
         isUpdatingUI = true;
 
@@ -189,7 +196,9 @@ public class AppointmentDetailFragment extends Fragment {
 
     private void loadAppointmentData() {
         viewModel.loadAppointment().observe(getViewLifecycleOwner(), resource -> {
-            if (resource == null || resource.status != Resource.Status.SUCCESS || resource.data == null) return;
+            if (resource == null) return;
+            setLoading(resource.status == Resource.Status.LOADING);
+            if (resource.status == Resource.Status.SUCCESS && resource.data != null) {
                 AppointmentDTO a = resource.data;
                 preselectedPetId = a.getPetId() != null ? a.getPetId() : -1;
                 preselectedServiceId = a.getServiceId() != null ? a.getServiceId() : -1;
@@ -205,6 +214,7 @@ public class AppointmentDetailFragment extends Fragment {
                     SpinnerUtils.setSelectionByValue(binding.spinnerAppointmentStatus, DateTimeUtils.formatStatusFromBackend(status));
                 }
                 notifyDateTimeStatusChange();
+            }
         });
     }
 
@@ -221,6 +231,8 @@ public class AppointmentDetailFragment extends Fragment {
         }
 
         viewModel.saveAppointment(date, time, status).observe(getViewLifecycleOwner(), resource -> {
+            if (resource == null) return;
+            setLoading(resource.status == Resource.Status.LOADING);
             if (resource.status == Resource.Status.SUCCESS) {
                 AppointmentDetailViewModel.ViewState state = viewModel.getViewState().getValue();
                 String message = (state != null && state.isEditing) ? "Updated" : "Saved";
@@ -233,11 +245,11 @@ public class AppointmentDetailFragment extends Fragment {
     }
 
     private boolean validateRequiredFields() {
-        if (binding.spinnerCustomer.getSelectedItemPosition() == 0) return UIUtils.showToast(getContext(), "Select a customer");
+        if (!InputValidator.isSpinnerSelected(binding.spinnerCustomer, "Customer")) return false;
-        if (binding.spinnerStore.getSelectedItemPosition() == 0) return UIUtils.showToast(getContext(), "Select a store");
+        if (!InputValidator.isSpinnerSelected(binding.spinnerStore, "Store")) return false;
-        if (binding.spinnerPet.getSelectedItemPosition() == 0) return UIUtils.showToast(getContext(), "Select a pet");
+        if (!InputValidator.isSpinnerSelected(binding.spinnerPet, "Pet")) return false;
-        if (binding.spinnerService.getSelectedItemPosition() == 0) return UIUtils.showToast(getContext(), "Select a service");
+        if (!InputValidator.isSpinnerSelected(binding.spinnerService, "Service")) return false;
-        if (binding.etAppointmentDate.getText().toString().trim().isEmpty()) return UIUtils.showToast(getContext(), "Select a date");
+        if (!InputValidator.isNotEmpty(binding.etAppointmentDate, "Appointment Date")) return false;
         return true;
     }
 
@@ -261,6 +273,8 @@ public class AppointmentDetailFragment extends Fragment {
     private void confirmDelete() {
         DialogUtils.showDeleteConfirmDialog(requireContext(), "Appointment", () ->
                 viewModel.deleteAppointment().observe(getViewLifecycleOwner(), resource -> {
+                    if (resource == null) return;
+                    setLoading(resource.status == Resource.Status.LOADING);
                     if (resource.status == Resource.Status.SUCCESS) navigateBack();
                 }));
     }

android/app/src/main/java/com/example/petstoremobile/fragments/listfragments/detailfragments/InventoryDetailFragment.java

@@ -8,7 +8,6 @@ import android.widget.Toast;
 
 import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
-import androidx.appcompat.app.AlertDialog;
 import androidx.fragment.app.Fragment;
 import androidx.lifecycle.ViewModelProvider;
 import androidx.navigation.fragment.NavHostFragment;
@@ -17,9 +16,11 @@ import com.example.petstoremobile.databinding.FragmentInventoryDetailBinding;
 import com.example.petstoremobile.dtos.DropdownDTO;
 import com.example.petstoremobile.dtos.InventoryDTO;
 import com.example.petstoremobile.dtos.ProductDTO;
+import com.example.petstoremobile.utils.DialogUtils;
 import com.example.petstoremobile.utils.InputValidator;
 import com.example.petstoremobile.utils.Resource;
 import com.example.petstoremobile.utils.SpinnerUtils;
+import com.example.petstoremobile.utils.UIUtils;
 import com.example.petstoremobile.viewmodels.InventoryDetailViewModel;
 
 import dagger.hilt.android.AndroidEntryPoint;
@@ -67,6 +68,12 @@ public class InventoryDetailFragment extends Fragment {
         viewModel.getProductList().observe(getViewLifecycleOwner(), list -> refreshProductSpinner());
     }
 
+    private void setLoading(boolean loading) {
+        if (binding != null && binding.progressBar != null) {
+            binding.progressBar.setVisibility(loading ? View.VISIBLE : View.GONE);
+        }
+    }
+
     @Override
     public void onDestroyView() {
         super.onDestroyView();
@@ -75,11 +82,15 @@ public class InventoryDetailFragment extends Fragment {
 
     private void loadSpinnersData() {
         viewModel.loadStores().observe(getViewLifecycleOwner(), resource -> {
+            if (resource == null) return;
+            setLoading(resource.status == Resource.Status.LOADING);
             if (resource.status == Resource.Status.SUCCESS && resource.data != null) {
                 viewModel.setStoreList(resource.data);
             }
         });
         viewModel.loadProducts().observe(getViewLifecycleOwner(), resource -> {
+            if (resource == null) return;
+            setLoading(resource.status == Resource.Status.LOADING);
             if (resource.status == Resource.Status.SUCCESS && resource.data != null) {
                 viewModel.setProductList(resource.data.getContent());
             }
@@ -123,6 +134,7 @@ public class InventoryDetailFragment extends Fragment {
     private void loadInventoryData() {
         viewModel.loadInventory().observe(getViewLifecycleOwner(), resource -> {
             if (resource == null) return;
+            setLoading(resource.status == Resource.Status.LOADING);
             if (resource.status == Resource.Status.SUCCESS && resource.data != null) {
                 InventoryDTO inv = resource.data;
                 binding.etQuantity.setText(String.valueOf(inv.getQuantity()));
@@ -138,19 +150,9 @@ public class InventoryDetailFragment extends Fragment {
     }
 
     private void saveInventory() {
-        if (binding.spinnerInventoryStore.getSelectedItemPosition() == 0) {
+        if (!InputValidator.isSpinnerSelected(binding.spinnerInventoryStore, "Store")) return;
-            Toast.makeText(getContext(), "Please select a store", Toast.LENGTH_SHORT).show();
+        if (!InputValidator.isSpinnerSelected(binding.spinnerInventoryProduct, "Product")) return;
-            return;
+        if (!InputValidator.isPositiveInteger(binding.etQuantity, "Quantity")) return;
-        }
-        if (binding.spinnerInventoryProduct.getSelectedItemPosition() == 0) {
-            Toast.makeText(getContext(), "Please select a product", Toast.LENGTH_SHORT).show();
-            return;
-        }
-
-        if (!InputValidator.isNotEmpty(binding.etQuantity, "Quantity") ||
-            !InputValidator.isPositiveInteger(binding.etQuantity, "Quantity")) {
-            return;
-        }
 
         int quantity = Integer.parseInt(binding.etQuantity.getText().toString().trim());
         DropdownDTO store = viewModel.getStoreList().getValue().get(binding.spinnerInventoryStore.getSelectedItemPosition() - 1);
@@ -160,6 +162,9 @@ public class InventoryDetailFragment extends Fragment {
         setButtonsEnabled(false);
 
         viewModel.saveInventory(request).observe(getViewLifecycleOwner(), resource -> {
+            if (resource == null) return;
+            setLoading(resource.status == Resource.Status.LOADING);
+            if (resource.status != Resource.Status.LOADING) {
                 setButtonsEnabled(true);
                 if (resource.status == Resource.Status.SUCCESS) {
                     Toast.makeText(getContext(), viewModel.isEditing() ? "Inventory updated" : "Inventory created", Toast.LENGTH_SHORT).show();
@@ -167,21 +172,20 @@ public class InventoryDetailFragment extends Fragment {
                 } else if (resource.status == Resource.Status.ERROR) {
                     Toast.makeText(getContext(), "Error: " + resource.message, Toast.LENGTH_SHORT).show();
                 }
+            }
         });
     }
 
     private void confirmDelete() {
-        new AlertDialog.Builder(requireContext())
+        DialogUtils.showDeleteConfirmDialog(requireContext(), "Inventory Item", this::deleteInventory);
-                .setTitle("Delete inventory item?")
-                .setMessage("This cannot be undone.")
-                .setPositiveButton("Delete", (d, w) -> deleteInventory())
-                .setNegativeButton("Cancel", null)
-                .show();
     }
 
     private void deleteInventory() {
         setButtonsEnabled(false);
         viewModel.deleteInventory().observe(getViewLifecycleOwner(), resource -> {
+            if (resource == null) return;
+            setLoading(resource.status == Resource.Status.LOADING);
+            if (resource.status != Resource.Status.LOADING) {
                 setButtonsEnabled(true);
                 if (resource.status == Resource.Status.SUCCESS) {
                     Toast.makeText(getContext(), "Inventory deleted", Toast.LENGTH_SHORT).show();
@@ -189,6 +193,7 @@ public class InventoryDetailFragment extends Fragment {
                 } else if (resource.status == Resource.Status.ERROR) {
                     Toast.makeText(getContext(), "Delete failed: " + resource.message, Toast.LENGTH_SHORT).show();
                 }
+            }
         });
     }
 
@@ -197,8 +202,6 @@ public class InventoryDetailFragment extends Fragment {
     }
 
     private void setButtonsEnabled(boolean enabled) {
-        binding.btnSaveInventory.setEnabled(enabled);
+        UIUtils.setViewsEnabled(enabled, binding.btnSaveInventory, binding.btnDeleteInventory, binding.btnInventoryBack);
-        binding.btnDeleteInventory.setEnabled(enabled);
-        binding.btnInventoryBack.setEnabled(enabled);
     }
 }

android/app/src/main/java/com/example/petstoremobile/fragments/listfragments/detailfragments/PetDetailFragment.java

@@ -21,6 +21,7 @@ import com.example.petstoremobile.databinding.FragmentPetDetailBinding;
 import com.example.petstoremobile.dtos.DropdownDTO;
 import com.example.petstoremobile.dtos.PetDTO;
 import com.example.petstoremobile.utils.ActivityLogger;
+import com.example.petstoremobile.utils.DateTimeUtils;
 import com.example.petstoremobile.utils.DialogUtils;
 import com.example.petstoremobile.utils.InputValidator;
 import com.example.petstoremobile.utils.Resource;
@@ -65,7 +66,6 @@ public class PetDetailFragment extends Fragment {
         observeViewModel();
         handleArguments();
 
-        //set button click listeners
         binding.btnBack.setOnClickListener(v -> navigateBack());
         binding.btnSavePet.setOnClickListener(v -> savePet());
         binding.btnDeletePet.setOnClickListener(v -> deletePet());
@@ -76,36 +76,41 @@ public class PetDetailFragment extends Fragment {
         viewModel.getStoreList().observe(getViewLifecycleOwner(), list -> updateStoreSpinnerSelection());
         
         viewModel.loadCustomers().observe(getViewLifecycleOwner(), resource -> {
-            if (resource != null && resource.status == Resource.Status.SUCCESS && resource.data != null) {
+            if (resource == null) return;
+            setLoading(resource.status == Resource.Status.LOADING);
+            if (resource.status == Resource.Status.SUCCESS && resource.data != null) {
                 viewModel.setCustomerList(resource.data);
             }
         });
 
         viewModel.loadStores().observe(getViewLifecycleOwner(), resource -> {
-            if (resource != null && resource.status == Resource.Status.SUCCESS && resource.data != null) {
+            if (resource == null) return;
+            setLoading(resource.status == Resource.Status.LOADING);
+            if (resource.status == Resource.Status.SUCCESS && resource.data != null) {
                 viewModel.setStoreList(resource.data);
             }
         });
     }
 
+    private void setLoading(boolean loading) {
+        if (binding != null && binding.progressBar != null) {
+            binding.progressBar.setVisibility(loading ? View.VISIBLE : View.GONE);
+        }
+    }
+
     @Override
     public void onDestroyView() {
         super.onDestroyView();
         binding = null;
     }
 
-    /**
-     * Handles the saving of pet data (adding/updating).
-     */
     private void savePet() {
-        // Validates all fields using InputValidator
         if (!InputValidator.isNotEmpty(binding.etPetName, "Pet Name")) return;
         if (!InputValidator.isNotEmpty(binding.etPetSpecies, "Species")) return;
         if (!InputValidator.isNotEmpty(binding.etPetBreed, "Breed")) return;
         if (!InputValidator.isPositiveInteger(binding.etPetAge, "Age")) return;
         if (!InputValidator.isPositiveDecimal(binding.etPetPrice, "Price")) return;
 
-        //get all the values from the fields
         String name = binding.etPetName.getText().toString().trim();
         String species = binding.etPetSpecies.getText().toString().trim();
         String breed = binding.etPetBreed.getText().toString().trim();
@@ -113,37 +118,27 @@ public class PetDetailFragment extends Fragment {
         double price = Double.parseDouble(binding.etPetPrice.getText().toString().trim());
         String status = binding.spinnerPetStatus.getSelectedItem().toString();
 
-        // Get selected customer
         Long customerId = null;
-        int customerPos = binding.spinnerCustomer.getSelectedItemPosition();
+        if (binding.spinnerCustomer.getSelectedItemPosition() > 0) {
-        if (customerPos > 0) { // 0 means no customer for pet
+            customerId = viewModel.getCustomerList().getValue().get(binding.spinnerCustomer.getSelectedItemPosition() - 1).getId();
-            customerId = viewModel.getCustomerList().getValue().get(customerPos - 1).getId();
         }
 
-        // Get selected store
         Long storeId = null;
-        int storePos = binding.spinnerStore.getSelectedItemPosition();
+        if (binding.spinnerStore.getSelectedItemPosition() > 0) {
-        if (storePos > 0) {
+            storeId = viewModel.getStoreList().getValue().get(binding.spinnerStore.getSelectedItemPosition() - 1).getId();
-            storeId = viewModel.getStoreList().getValue().get(storePos - 1).getId();
         }
 
-        // Validation: If status is Available, a store must be selected
         if ("Available".equalsIgnoreCase(status)) {
             if (!InputValidator.isSpinnerSelected(binding.spinnerStore, "Store")) return;
         }
-
-        // Validation: If status is Owned, an owner must be selected
         if ("Owned".equalsIgnoreCase(status)) {
             if (!InputValidator.isSpinnerSelected(binding.spinnerCustomer, "Owner")) return;
         }
-
-        // Validation: If status is Adopted, an owner and store must be selected
         if ("Adopted".equalsIgnoreCase(status)) {
             if (!InputValidator.isSpinnerSelected(binding.spinnerCustomer, "Owner")) return;
             if (!InputValidator.isSpinnerSelected(binding.spinnerStore, "Store")) return;
         }
 
-        //create a pet object to send to the API
         PetDTO petDTO = new PetDTO();
         petDTO.setPetName(name);
         petDTO.setPetSpecies(species);
@@ -155,6 +150,8 @@ public class PetDetailFragment extends Fragment {
         petDTO.setStoreId(storeId);
 
         viewModel.savePet(petDTO).observe(getViewLifecycleOwner(), resource -> {
+            if (resource == null) return;
+            setLoading(resource.status == Resource.Status.LOADING);
             if (resource.status == Resource.Status.SUCCESS) {
                 if (viewModel.isEditing()) {
                     ActivityLogger.logChange(requireContext(), "Pet", "UPDATED", (int) viewModel.getPetId());
@@ -170,12 +167,11 @@ public class PetDetailFragment extends Fragment {
         });
     }
 
-    /**
-     * Displays a confirmation dialog and handles the deletion of a pet.
-     */
     private void deletePet() {
-        DialogUtils.showDeleteConfirmDialog(requireContext(), "Pet", () -> 
+        DialogUtils.showDeleteConfirmDialog(requireContext(), "Pet", () -> {
                 viewModel.deletePet().observe(getViewLifecycleOwner(), resource -> {
+                    if (resource == null) return;
+                    setLoading(resource.status == Resource.Status.LOADING);
                     if (resource.status == Resource.Status.SUCCESS) {
                         ActivityLogger.logChange(requireContext(), "Pet", "DELETED", (int) viewModel.getPetId());
                         Toast.makeText(getContext(), "Pet deleted successfully!", Toast.LENGTH_SHORT).show();
@@ -183,32 +179,24 @@ public class PetDetailFragment extends Fragment {
                     } else if (resource.status == Resource.Status.ERROR) {
                         Toast.makeText(getContext(), "Delete failed: " + resource.message, Toast.LENGTH_SHORT).show();
                     }
-                }));
+                });
+        });
     }
 
-    /**
-     * Navigates back to the pet list screen.
-     */
     private void navigateToPetList() {
         NavHostFragment.findNavController(this).popBackStack(R.id.nav_pet, false);
     }
 
-    /**
-     * Navigates back to the previous screen.
-     */
     private void navigateBack() {
         NavHostFragment.findNavController(this).popBackStack();
     }
 
-    /**
-     * Handles arguments passed to the fragment to determine if it's in edit or add mode.
-     */
     private void handleArguments() {
         if (getArguments() != null && getArguments().containsKey("petId")) {
             long petId = getArguments().getLong("petId");
             viewModel.setPetId(petId);
             binding.tvMode.setText("Edit Pet");
-            binding.tvPetId.setText("ID: " + petId);
+            binding.tvPetId.setText(DateTimeUtils.formatId(petId));
             binding.tvPetId.setVisibility(View.VISIBLE);
             binding.btnDeletePet.setVisibility(View.VISIBLE);
             
@@ -225,12 +213,10 @@ public class PetDetailFragment extends Fragment {
         }
     }
 
-    /**
-     * Fetches specific pet details from the backend using the ID.
-     */
     private void loadPetData() {
         viewModel.loadPet().observe(getViewLifecycleOwner(), resource -> {
             if (resource == null) return;
+            setLoading(resource.status == Resource.Status.LOADING);
             if (resource.status == Resource.Status.SUCCESS && resource.data != null) {
                 PetDTO p = resource.data;
                 binding.etPetName.setText(p.getPetName());
@@ -253,9 +239,6 @@ public class PetDetailFragment extends Fragment {
         });
     }
 
-    /**
-     * Updates the customer spinner with the current list and sets the selection if needed.
-     */
     private void updateCustomerSpinnerSelection() {
         SpinnerUtils.populateSpinner(
                 requireContext(),
@@ -268,9 +251,6 @@ public class PetDetailFragment extends Fragment {
         );
     }
 
-    /**
-     * Updates the store spinner with the current list and sets the selection if needed.
-     */
     private void updateStoreSpinnerSelection() {
         SpinnerUtils.populateSpinner(
                 requireContext(),
@@ -283,9 +263,6 @@ public class PetDetailFragment extends Fragment {
         );
     }
 
-    /**
-     * Initializes the spinner for pet status selection.
-     */
     private void setupSpinner() {
         SpinnerUtils.setupStringSpinner(requireContext(), binding.spinnerPetStatus,
                 new String[]{"Available", "Adopted", "Owned"});

android/app/src/main/java/com/example/petstoremobile/fragments/listfragments/detailfragments/ProductDetailFragment.java

@@ -18,6 +18,7 @@ import com.example.petstoremobile.api.auth.TokenManager;
 import com.example.petstoremobile.databinding.FragmentProductDetailBinding;
 import com.example.petstoremobile.dtos.*;
 import com.example.petstoremobile.viewmodels.ProductDetailViewModel;
+import com.example.petstoremobile.utils.DateTimeUtils;
 import com.example.petstoremobile.utils.DialogUtils;
 import com.example.petstoremobile.utils.FileUtils;
 import com.example.petstoremobile.utils.GlideUtils;
@@ -111,12 +112,20 @@ public class ProductDetailFragment extends Fragment {
         viewModel.getCategoryList().observe(getViewLifecycleOwner(), list -> updateCategorySpinner());
         
         viewModel.loadCategories().observe(getViewLifecycleOwner(), resource -> {
-            if (resource != null && resource.status == Resource.Status.SUCCESS && resource.data != null) {
+            if (resource == null) return;
+            setLoading(resource.status == Resource.Status.LOADING);
+            if (resource.status == Resource.Status.SUCCESS && resource.data != null) {
                 viewModel.setCategoryList(resource.data.getContent());
             }
         });
     }
 
+    private void setLoading(boolean loading) {
+        if (binding != null && binding.progressBar != null) {
+            binding.progressBar.setVisibility(loading ? View.VISIBLE : View.GONE);
+        }
+    }
+
     private void updateCategorySpinner() {
         SpinnerUtils.populateSpinner(requireContext(), binding.spinnerProductCategory, viewModel.getCategoryList().getValue(),
                 CategoryDTO::getCategoryName, "-- Select Category --",
@@ -135,7 +144,7 @@ public class ProductDetailFragment extends Fragment {
             long prodId = a.getLong("prodId");
             viewModel.setProdId(prodId);
             binding.tvProductMode.setText("Edit Product");
-            binding.tvProductId.setText("ID: " + prodId);
+            binding.tvProductId.setText(DateTimeUtils.formatId(prodId));
             binding.tvProductId.setVisibility(View.VISIBLE);
             binding.btnDeleteProduct.setVisibility(View.VISIBLE);
             loadProductData();
@@ -152,6 +161,7 @@ public class ProductDetailFragment extends Fragment {
     private void loadProductData() {
         viewModel.loadProduct().observe(getViewLifecycleOwner(), resource -> {
             if (resource == null) return;
+            setLoading(resource.status == Resource.Status.LOADING);
             if (resource.status == Resource.Status.SUCCESS && resource.data != null) {
                 ProductDTO p = resource.data;
                 binding.etProductName.setText(p.getProdName());
@@ -185,7 +195,9 @@ public class ProductDetailFragment extends Fragment {
     private void performPendingImageActions(String successMsg) {
         if (isImageRemoved) {
             viewModel.deleteProductImage().observe(getViewLifecycleOwner(), resource -> {
-                if (resource != null && resource.status != Resource.Status.LOADING) {
+                if (resource == null) return;
+                setLoading(resource.status == Resource.Status.LOADING);
+                if (resource.status != Resource.Status.LOADING) {
                     if (resource.status == Resource.Status.SUCCESS) {
                         Toast.makeText(getContext(), successMsg, Toast.LENGTH_SHORT).show();
                     } else {
@@ -214,7 +226,9 @@ public class ProductDetailFragment extends Fragment {
         MultipartBody.Part body = MultipartBody.Part.createFormData("image", file.getName(), requestFile);
 
         viewModel.uploadProductImage(body).observe(getViewLifecycleOwner(), resource -> {
-            if (resource != null && resource.status != Resource.Status.LOADING) {
+            if (resource == null) return;
+            setLoading(resource.status == Resource.Status.LOADING);
+            if (resource.status != Resource.Status.LOADING) {
                 if (resource.status == Resource.Status.SUCCESS) {
                     Toast.makeText(getContext(), successMsg, Toast.LENGTH_SHORT).show();
                 } else {
@@ -227,15 +241,8 @@ public class ProductDetailFragment extends Fragment {
 
     private void saveProduct() {
         if (!InputValidator.isNotEmpty(binding.etProductName, "Product Name")) return;
-
+        if (!InputValidator.isSpinnerSelected(binding.spinnerProductCategory, "Category")) return;
-        if (binding.spinnerProductCategory.getSelectedItemPosition() == 0) {
+        if (!InputValidator.isPositiveDecimal(binding.etProductPrice, "Price")) return;
-            Toast.makeText(getContext(), "Select a category", Toast.LENGTH_SHORT).show(); return;
-        }
-
-        if (!InputValidator.isNotEmpty(binding.etProductPrice, "Price") ||
-            !InputValidator.isPositiveDecimal(binding.etProductPrice, "Price")) {
-            return;
-        }
 
         String name = binding.etProductName.getText().toString().trim();
         String desc = binding.etProductDesc.getText().toString().trim();
@@ -245,7 +252,9 @@ public class ProductDetailFragment extends Fragment {
         ProductDTO dto = new ProductDTO(name, category.getCategoryId(), desc, price);
 
         viewModel.saveProduct(dto).observe(getViewLifecycleOwner(), resource -> {
-            if (resource != null && resource.status != Resource.Status.LOADING) {
+            if (resource == null) return;
+            setLoading(resource.status == Resource.Status.LOADING);
+            if (resource.status != Resource.Status.LOADING) {
                 if (resource.status == Resource.Status.SUCCESS) {
                     if (resource.data != null) {
                         viewModel.setProdId(resource.data.getProdId());
@@ -261,9 +270,11 @@ public class ProductDetailFragment extends Fragment {
     private void confirmDelete() {
         DialogUtils.showDeleteConfirmDialog(requireContext(), "Product", () -> 
                 viewModel.deleteProduct().observe(getViewLifecycleOwner(), resource -> {
-                    if (resource != null && resource.status == Resource.Status.SUCCESS) {
+                    if (resource == null) return;
+                    setLoading(resource.status == Resource.Status.LOADING);
+                    if (resource.status == Resource.Status.SUCCESS) {
                         navigateBack();
-                    } else if (resource != null && resource.status == Resource.Status.ERROR) {
+                    } else if (resource.status == Resource.Status.ERROR) {
                         Toast.makeText(getContext(), "Delete failed: " + resource.message, Toast.LENGTH_SHORT).show();
                     }
                 }));

android/app/src/main/java/com/example/petstoremobile/fragments/listfragments/detailfragments/ProductSupplierDetailFragment.java

@@ -15,6 +15,7 @@ import com.example.petstoremobile.utils.DialogUtils;
 import com.example.petstoremobile.utils.InputValidator;
 import com.example.petstoremobile.utils.Resource;
 import com.example.petstoremobile.utils.SpinnerUtils;
+import com.example.petstoremobile.utils.UIUtils;
 import com.example.petstoremobile.viewmodels.ProductSupplierDetailViewModel;
 
 import java.math.BigDecimal;
@@ -64,6 +65,12 @@ public class ProductSupplierDetailFragment extends Fragment {
         viewModel.getSupplierList().observe(getViewLifecycleOwner(), list -> refreshSupplierSpinner());
     }
 
+    private void setLoading(boolean loading) {
+        if (binding != null && binding.progressBar != null) {
+            binding.progressBar.setVisibility(loading ? View.VISIBLE : View.GONE);
+        }
+    }
+
     @Override
     public void onDestroyView() {
         super.onDestroyView();
@@ -72,11 +79,15 @@ public class ProductSupplierDetailFragment extends Fragment {
 
     private void loadSpinnersData() {
         viewModel.loadProducts().observe(getViewLifecycleOwner(), resource -> {
+            if (resource == null) return;
+            setLoading(resource.status == Resource.Status.LOADING);
             if (resource.status == Resource.Status.SUCCESS && resource.data != null) {
                 viewModel.setProductList(resource.data.getContent());
             }
         });
         viewModel.loadSuppliers().observe(getViewLifecycleOwner(), resource -> {
+            if (resource == null) return;
+            setLoading(resource.status == Resource.Status.LOADING);
             if (resource.status == Resource.Status.SUCCESS && resource.data != null) {
                 viewModel.setSupplierList(resource.data.getContent());
             }
@@ -113,17 +124,9 @@ public class ProductSupplierDetailFragment extends Fragment {
     }
 
     private void save() {
-        if (binding.spinnerPSProduct.getSelectedItemPosition() == 0) {
+        if (!InputValidator.isSpinnerSelected(binding.spinnerPSProduct, "Product")) return;
-            Toast.makeText(getContext(), "Select a product", Toast.LENGTH_SHORT).show(); return;
+        if (!InputValidator.isSpinnerSelected(binding.spinnerPSSupplier, "Supplier")) return;
-        }
+        if (!InputValidator.isPositiveDecimal(binding.etPSCost, "Cost")) return;
-        if (binding.spinnerPSSupplier.getSelectedItemPosition() == 0) {
-            Toast.makeText(getContext(), "Select a supplier", Toast.LENGTH_SHORT).show(); return;
-        }
-
-        if (!InputValidator.isNotEmpty(binding.etPSCost, "Cost") ||
-            !InputValidator.isPositiveDecimal(binding.etPSCost, "Cost")) {
-            return;
-        }
 
         ProductDTO product   = viewModel.getProductList().getValue().get(binding.spinnerPSProduct.getSelectedItemPosition() - 1);
         SupplierDTO supplier = viewModel.getSupplierList().getValue().get(binding.spinnerPSSupplier.getSelectedItemPosition() - 1);
@@ -132,6 +135,8 @@ public class ProductSupplierDetailFragment extends Fragment {
         ProductSupplierDTO dto = new ProductSupplierDTO(product.getProdId(), supplier.getSupId(), cost);
 
         viewModel.saveProductSupplier(dto).observe(getViewLifecycleOwner(), resource -> {
+            if (resource == null) return;
+            setLoading(resource.status == Resource.Status.LOADING);
             if (resource.status == Resource.Status.SUCCESS) {
                 Toast.makeText(getContext(), viewModel.isEditing() ? "Updated" : "Saved", Toast.LENGTH_SHORT).show();
                 navigateBack();
@@ -142,8 +147,10 @@ public class ProductSupplierDetailFragment extends Fragment {
     }
 
     private void confirmDelete() {
-        DialogUtils.showDeleteConfirmDialog(requireContext(), "Product Supplier", () ->
+        DialogUtils.showDeleteConfirmDialog(requireContext(), "Product Supplier Relationship", () ->
                 viewModel.deleteProductSupplier().observe(getViewLifecycleOwner(), resource -> {
+                    if (resource == null) return;
+                    setLoading(resource.status == Resource.Status.LOADING);
                     if (resource.status == Resource.Status.SUCCESS) {
                         Toast.makeText(getContext(), "Deleted", Toast.LENGTH_SHORT).show();
                         navigateBack();

android/app/src/main/java/com/example/petstoremobile/fragments/listfragments/detailfragments/PurchaseOrderDetailFragment.java

@@ -66,9 +66,16 @@ public class PurchaseOrderDetailFragment extends Fragment {
         }
     }
 
+    private void setLoading(boolean loading) {
+        if (binding != null && binding.progressBar != null) {
+            binding.progressBar.setVisibility(loading ? View.VISIBLE : View.GONE);
+        }
+    }
+
     private void loadPurchaseOrderData() {
         viewModel.loadPurchaseOrder(purchaseOrderId).observe(getViewLifecycleOwner(), resource -> {
             if (resource == null) return;
+            setLoading(resource.status == Resource.Status.LOADING);
             if (resource.status == Resource.Status.SUCCESS && resource.data != null) {
                 PurchaseOrderDTO po = resource.data;
                 binding.tvPODetailId.setText("PO #" + po.getPurchaseOrderId());

android/app/src/main/java/com/example/petstoremobile/fragments/listfragments/detailfragments/RefundFragment.java

@@ -1,6 +1,5 @@
 package com.example.petstoremobile.fragments.listfragments.detailfragments;
 
-import android.app.AlertDialog;
 import android.os.Bundle;
 import android.util.Log;
 import android.view.*;
@@ -13,7 +12,9 @@ import com.example.petstoremobile.R;
 import com.example.petstoremobile.databinding.FragmentRefundBinding;
 import com.example.petstoremobile.dtos.SaleDTO;
 import com.example.petstoremobile.viewmodels.RefundViewModel;
+import com.example.petstoremobile.utils.DialogUtils;
 import com.example.petstoremobile.utils.Resource;
+import com.example.petstoremobile.utils.SpinnerUtils;
 import dagger.hilt.android.AndroidEntryPoint;
 import java.math.BigDecimal;
 import java.math.RoundingMode;
@@ -50,8 +51,7 @@ public class RefundFragment extends Fragment {
     }
 
     private void setupSpinner() {
-        binding.spinnerRefundPayment.setAdapter(new ArrayAdapter<>(requireContext(),
+        SpinnerUtils.setupStringSpinner(requireContext(), binding.spinnerRefundPayment, PAYMENT_METHODS);
-                android.R.layout.simple_spinner_item, PAYMENT_METHODS));
     }
 
     private void observeViewModel() {
@@ -63,9 +63,17 @@ public class RefundFragment extends Fragment {
         });
     }
 
+    private void setLoading(boolean loading) {
+        if (binding != null && binding.progressBar != null) {
+            binding.progressBar.setVisibility(loading ? View.VISIBLE : View.GONE);
+        }
+    }
+
     private void loadAllSales() {
         viewModel.loadAllSales().observe(getViewLifecycleOwner(), resource -> {
-            if (resource != null && resource.status == Resource.Status.SUCCESS && resource.data != null) {
+            if (resource == null) return;
+            setLoading(resource.status == Resource.Status.LOADING);
+            if (resource.status == Resource.Status.SUCCESS && resource.data != null) {
                 viewModel.setAllSales(resource.data.getContent());
                 Bundle args = getArguments();
                 if (args != null && args.containsKey("saleId")) {
@@ -122,11 +130,7 @@ public class RefundFragment extends Fragment {
                 + " | Payment: " + currentSale.getPaymentMethod());
 
         if (currentSale.getPaymentMethod() != null) {
-            for (int i = 0; i < PAYMENT_METHODS.length; i++) {
+            SpinnerUtils.setSelectionByValue(binding.spinnerRefundPayment, currentSale.getPaymentMethod());
-                if (PAYMENT_METHODS[i].equalsIgnoreCase(currentSale.getPaymentMethod())) {
-                    binding.spinnerRefundPayment.setSelection(i); break;
-                }
-            }
         }
 
         if (viewModel.getAvailableItems().getValue() == null || viewModel.getAvailableItems().getValue().isEmpty()) {
@@ -263,17 +267,17 @@ public class RefundFragment extends Fragment {
     }
 
     private void showQuantityDialog(RefundViewModel.RefundItem item, int available) {
-        AlertDialog.Builder builder = new AlertDialog.Builder(requireContext());
-        builder.setTitle("Refund Quantity");
-        builder.setMessage("Product: " + item.productName + "\nAvailable: " + available);
-
         EditText input = new EditText(getContext());
         input.setInputType(android.text.InputType.TYPE_CLASS_NUMBER);
         input.setText(String.valueOf(available));
         input.setSelectAllOnFocus(true);
-        builder.setView(input);
+        input.setPadding(40, 40, 40, 40);
 
-        builder.setPositiveButton("Add to Refund", (d, w) -> {
+        new androidx.appcompat.app.AlertDialog.Builder(requireContext())
+                .setTitle("Refund Quantity")
+                .setMessage("Product: " + item.productName + "\nAvailable: " + available)
+                .setView(input)
+                .setPositiveButton("Add to Refund", (d, w) -> {
                     String val = input.getText().toString().trim();
                     if (val.isEmpty()) return;
                     int qty;
@@ -290,12 +294,10 @@ public class RefundFragment extends Fragment {
                         Toast.makeText(getContext(), "Cannot exceed " + available, Toast.LENGTH_SHORT).show();
                         return;
                     }
-
                     viewModel.addToCart(item, qty);
-        });
+                })
-
+                .setNegativeButton("Cancel", null)
-        builder.setNegativeButton("Cancel", null);
+                .show();
-        builder.show();
     }
 
     private void updateRefundTotal() {
@@ -322,18 +324,16 @@ public class RefundFragment extends Fragment {
         for (RefundViewModel.RefundItem item : viewModel.getRefundCart().getValue()) total = total.add(item.getTotal());
         final BigDecimal finalTotal = total;
 
-        new AlertDialog.Builder(requireContext())
+        DialogUtils.showConfirmDialog(requireContext(), "Confirm Refund", 
-                .setTitle("Confirm Refund")
+                "Process refund for Sale #" + viewModel.getCurrentSale().getSaleId()
-                .setMessage("Process refund for Sale #" + viewModel.getCurrentSale().getSaleId()
+                        + "?\nRefund amount: $" + finalTotal.setScale(2, RoundingMode.HALF_UP),
-                        + "?\nRefund amount: $" + finalTotal.setScale(2, RoundingMode.HALF_UP))
+                () -> submitRefund(payment));
-                .setPositiveButton("Yes", (d, w) -> submitRefund(payment))
-                .setNegativeButton("No", null)
-                .show();
     }
 
     private void submitRefund(String payment) {
         viewModel.submitRefund(payment).observe(getViewLifecycleOwner(), resource -> {
             if (resource != null) {
+                setLoading(resource.status == Resource.Status.LOADING);
                 if (resource.status == Resource.Status.SUCCESS) {
                     Toast.makeText(getContext(), "Refund processed successfully!", Toast.LENGTH_LONG).show();
                     navigateBack();

android/app/src/main/java/com/example/petstoremobile/fragments/listfragments/detailfragments/SaleDetailFragment.java

@@ -14,6 +14,7 @@ import com.example.petstoremobile.dtos.*;
 import com.example.petstoremobile.viewmodels.SaleDetailViewModel;
 import com.example.petstoremobile.utils.SpinnerUtils;
 import com.example.petstoremobile.utils.DialogUtils;
+import com.example.petstoremobile.utils.InputValidator;
 import com.example.petstoremobile.utils.Resource;
 import com.example.petstoremobile.utils.UIUtils;
 import dagger.hilt.android.AndroidEntryPoint;
@@ -107,21 +108,35 @@ public class SaleDetailFragment extends Fragment {
         }
     }
 
+    private void setLoading(boolean loading) {
+        if (binding != null && binding.progressBar != null) {
+            binding.progressBar.setVisibility(loading ? View.VISIBLE : View.GONE);
+        }
+    }
+
     private void loadData() {
         viewModel.loadStores().observe(getViewLifecycleOwner(), resource -> {
+            if (resource == null) return;
+            setLoading(resource.status == Resource.Status.LOADING);
             if (resource.status == Resource.Status.SUCCESS && resource.data != null) viewModel.setStoreList(resource.data);
         });
         viewModel.loadCustomers().observe(getViewLifecycleOwner(), resource -> {
+            if (resource == null) return;
+            setLoading(resource.status == Resource.Status.LOADING);
             if (resource.status == Resource.Status.SUCCESS && resource.data != null) viewModel.setCustomerList(resource.data);
         });
         viewModel.loadProducts().observe(getViewLifecycleOwner(), resource -> {
+            if (resource == null) return;
+            setLoading(resource.status == Resource.Status.LOADING);
             if (resource.status == Resource.Status.SUCCESS && resource.data != null) viewModel.setProductList(resource.data.getContent());
         });
     }
 
     private void loadSaleDetails() {
         viewModel.loadSaleDetails().observe(getViewLifecycleOwner(), resource -> {
-            if (resource != null && resource.status == Resource.Status.SUCCESS && resource.data != null) {
+            if (resource == null) return;
+            setLoading(resource.status == Resource.Status.LOADING);
+            if (resource.status == Resource.Status.SUCCESS && resource.data != null) {
                 SaleDTO sale = resource.data;
                 binding.tvSaleDetailTotal.setText("Total: $" + sale.getTotalAmount());
                 binding.tvSaleSubtotal.setText("$" + (sale.getSubtotalAmount() != null ? sale.getSubtotalAmount() : sale.getTotalAmount()));
@@ -157,22 +172,10 @@ public class SaleDetailFragment extends Fragment {
 
     private void setupAddItem() {
         binding.btnAddItem.setOnClickListener(v -> {
-            if (binding.spinnerSaleProduct.getSelectedItemPosition() == 0) {
+            if (!InputValidator.isSpinnerSelected(binding.spinnerSaleProduct, "Product")) return;
-                Toast.makeText(getContext(), "Select a product", Toast.LENGTH_SHORT).show();
+            if (!InputValidator.isPositiveInteger(binding.etSaleQuantity, "Quantity")) return;
-                return;
-            }
-            String qtyStr = binding.etSaleQuantity.getText().toString().trim();
-            if (qtyStr.isEmpty()) {
-                binding.etSaleQuantity.setError("Enter quantity");
-                return;
-            }
-            int qty;
-            try { qty = Integer.parseInt(qtyStr); }
-            catch (Exception e) {
-                binding.etSaleQuantity.setError("Invalid quantity");
-                return;
-            }
 
+            int qty = Integer.parseInt(binding.etSaleQuantity.getText().toString().trim());
             ProductDTO product = viewModel.getProductList().getValue().get(binding.spinnerSaleProduct.getSelectedItemPosition() - 1);
 
             for (SaleDTO.SaleItemDTO existing : viewModel.getCartItems().getValue()) {
@@ -238,10 +241,8 @@ public class SaleDetailFragment extends Fragment {
     }
 
     private void saveSale() {
-        if (binding.spinnerSaleStore.getSelectedItemPosition() == 0) {
+        if (!InputValidator.isSpinnerSelected(binding.spinnerSaleStore, "Store")) return;
-            Toast.makeText(getContext(), "Select a store", Toast.LENGTH_SHORT).show();
+
-            return;
-        }
         if (viewModel.getCartItems().getValue() == null || viewModel.getCartItems().getValue().isEmpty()) {
             Toast.makeText(getContext(), "Add at least one item", Toast.LENGTH_SHORT).show();
             return;
@@ -259,6 +260,7 @@ public class SaleDetailFragment extends Fragment {
 
         viewModel.createSale(dto).observe(getViewLifecycleOwner(), resource -> {
             if (resource != null) {
+                setLoading(resource.status == Resource.Status.LOADING);
                 if (resource.status == Resource.Status.SUCCESS) {
                     Toast.makeText(getContext(), "Sale saved!", Toast.LENGTH_SHORT).show();
                     navigateBack();

android/app/src/main/java/com/example/petstoremobile/fragments/listfragments/detailfragments/ServiceDetailFragment.java

@@ -17,6 +17,7 @@ import com.example.petstoremobile.R;
 import com.example.petstoremobile.databinding.FragmentServiceDetailBinding;
 import com.example.petstoremobile.dtos.ServiceDTO;
 import com.example.petstoremobile.utils.ActivityLogger;
+import com.example.petstoremobile.utils.DateTimeUtils;
 import com.example.petstoremobile.utils.DialogUtils;
 import com.example.petstoremobile.utils.InputValidator;
 import com.example.petstoremobile.utils.Resource;
@@ -57,6 +58,12 @@ public class ServiceDetailFragment extends Fragment {
         binding.btnDeleteService.setOnClickListener(v -> deleteService());
     }
 
+    private void setLoading(boolean loading) {
+        if (binding != null && binding.progressBar != null) {
+            binding.progressBar.setVisibility(loading ? View.VISIBLE : View.GONE);
+        }
+    }
+
     @Override
     public void onDestroyView() {
         super.onDestroyView();
@@ -81,6 +88,8 @@ public class ServiceDetailFragment extends Fragment {
         serviceDTO.setServicePrice(price);
 
         viewModel.saveService(serviceDTO).observe(getViewLifecycleOwner(), resource -> {
+            if (resource == null) return;
+            setLoading(resource.status == Resource.Status.LOADING);
             if (resource.status == Resource.Status.SUCCESS) {
                 if (viewModel.isEditing()) {
                     ActivityLogger.logChange(requireContext(), "Service", "UPDATED", (int) viewModel.getServiceId());
@@ -99,6 +108,8 @@ public class ServiceDetailFragment extends Fragment {
     private void deleteService() {
         DialogUtils.showDeleteConfirmDialog(requireContext(), "Service", () -> 
                 viewModel.deleteService().observe(getViewLifecycleOwner(), resource -> {
+                    if (resource == null) return;
+                    setLoading(resource.status == Resource.Status.LOADING);
                     if (resource.status == Resource.Status.SUCCESS) {
                         ActivityLogger.logChange(requireContext(), "Service", "DELETED", (int) viewModel.getServiceId());
                         Toast.makeText(getContext(), "Service deleted successfully!", Toast.LENGTH_SHORT).show();
@@ -118,7 +129,7 @@ public class ServiceDetailFragment extends Fragment {
             long serviceId = getArguments().getLong("serviceId");
             viewModel.setServiceId(serviceId);
             binding.tvMode.setText("Edit Service");
-            binding.tvServiceId.setText("ID: " + serviceId);
+            binding.tvServiceId.setText(DateTimeUtils.formatId(serviceId));
             binding.btnDeleteService.setVisibility(View.VISIBLE);
             loadServiceData();
         } else {
@@ -133,6 +144,7 @@ public class ServiceDetailFragment extends Fragment {
     private void loadServiceData() {
         viewModel.loadService().observe(getViewLifecycleOwner(), resource -> {
             if (resource == null) return;
+            setLoading(resource.status == Resource.Status.LOADING);
             if (resource.status == Resource.Status.SUCCESS && resource.data != null) {
                 ServiceDTO s = resource.data;
                 binding.etServiceName.setText(s.getServiceName());

android/app/src/main/java/com/example/petstoremobile/fragments/listfragments/detailfragments/StaffDetailFragment.java

@@ -4,13 +4,16 @@ import android.os.Bundle;
 import android.view.*;
 import android.widget.*;
 import androidx.annotation.NonNull;
-import androidx.appcompat.app.AlertDialog;
 import androidx.fragment.app.Fragment;
 import androidx.lifecycle.ViewModelProvider;
 import androidx.navigation.fragment.NavHostFragment;
 import com.example.petstoremobile.R;
 import com.example.petstoremobile.databinding.FragmentStaffDetailBinding;
 import com.example.petstoremobile.dtos.EmployeeDTO;
+import com.example.petstoremobile.utils.DialogUtils;
+import com.example.petstoremobile.utils.InputValidator;
+import com.example.petstoremobile.utils.SpinnerUtils;
+import com.example.petstoremobile.utils.UIUtils;
 import com.example.petstoremobile.viewmodels.StaffDetailViewModel;
 import com.example.petstoremobile.utils.Resource;
 import dagger.hilt.android.AndroidEntryPoint;
@@ -36,14 +39,15 @@ public class StaffDetailFragment extends Fragment {
         binding.btnStaffBack.setOnClickListener(v -> navigateBack());
         binding.btnSaveStaff.setOnClickListener(v -> save());
         binding.btnDeleteStaff.setOnClickListener(v -> confirmDelete());
+        
+        UIUtils.formatPhoneInput(binding.etStaffPhone);
+        
         return binding.getRoot();
     }
 
     private void setupSpinners() {
-        binding.spinnerStaffRole.setAdapter(new ArrayAdapter<>(requireContext(),
+        SpinnerUtils.setupStringSpinner(requireContext(), binding.spinnerStaffRole, ROLES);
-                android.R.layout.simple_spinner_item, ROLES));
+        SpinnerUtils.setupStringSpinner(requireContext(), binding.spinnerStaffStatus, STATUSES);
-        binding.spinnerStaffStatus.setAdapter(new ArrayAdapter<>(requireContext(),
-                android.R.layout.simple_spinner_item, STATUSES));
     }
 
     private void handleArguments() {
@@ -62,16 +66,8 @@ public class StaffDetailFragment extends Fragment {
             binding.etStaffPhone.setText(a.getString("phone", ""));
             binding.btnDeleteStaff.setVisibility(View.VISIBLE);
 
-            String role = a.getString("role", "STAFF");
+            SpinnerUtils.setSelectionByValue(binding.spinnerStaffRole, a.getString("role", "STAFF"));
-            for (int i = 0; i < ROLES.length; i++) {
+            binding.spinnerStaffStatus.setSelection(a.getBoolean("active", true) ? 0 : 1);
-                if (ROLES[i].equals(role)) {
-                    binding.spinnerStaffRole.setSelection(i);
-                    break;
-                }
-            }
-
-            boolean active = a.getBoolean("active", true);
-            binding.spinnerStaffStatus.setSelection(active ? 0 : 1);
 
         } else {
             viewModel.setEmployeeId(-1, false);
@@ -81,29 +77,39 @@ public class StaffDetailFragment extends Fragment {
         }
     }
 
+    private void setLoading(boolean loading) {
+        if (binding != null && binding.progressBar != null) {
+            binding.progressBar.setVisibility(loading ? View.VISIBLE : View.GONE);
+        }
+    }
 
     private void save() {
-        String username  = binding.etStaffUsername.getText() != null ? binding.etStaffUsername.getText().toString().trim() : "";
+        if (!InputValidator.isNotEmpty(binding.etStaffUsername, "Username")) return;
-        String password  = binding.etStaffPassword.getText() != null ? binding.etStaffPassword.getText().toString().trim() : "";
+        
-        String firstName = binding.etStaffFirstName.getText() != null ? binding.etStaffFirstName.getText().toString().trim() : "";
+        if (!viewModel.isEditing()) {
-        String lastName  = binding.etStaffLastName.getText() != null ? binding.etStaffLastName.getText().toString().trim() : "";
+            if (!InputValidator.isNotEmpty(binding.etStaffPassword, "Password")) return;
-        String email     = binding.etStaffEmail.getText() != null ? binding.etStaffEmail.getText().toString().trim() : "";
+            String pass = binding.etStaffPassword.getText().toString();
-        String phone     = binding.etStaffPhone.getText() != null ? binding.etStaffPhone.getText().toString().trim() : "";
+            if (pass.length() < 6) {
+                binding.etStaffPassword.setError("At least 6 characters");
+                binding.etStaffPassword.requestFocus();
+                return;
+            }
+        }
+        
+        if (!InputValidator.isNotEmpty(binding.etStaffFirstName, "First Name")) return;
+        if (!InputValidator.isNotEmpty(binding.etStaffLastName, "Last Name")) return;
+        if (!InputValidator.isValidEmail(binding.etStaffEmail)) return;
+        if (!InputValidator.isValidPhone(binding.etStaffPhone)) return;
+
+        String username  = binding.etStaffUsername.getText().toString().trim();
+        String password  = binding.etStaffPassword.getText().toString().trim();
+        String firstName = binding.etStaffFirstName.getText().toString().trim();
+        String lastName  = binding.etStaffLastName.getText().toString().trim();
+        String email     = binding.etStaffEmail.getText().toString().trim();
+        String phone     = binding.etStaffPhone.getText().toString().trim();
         String role      = ROLES[binding.spinnerStaffRole.getSelectedItemPosition()];
         boolean active   = binding.spinnerStaffStatus.getSelectedItemPosition() == 0;
 
-        if (username.isEmpty()) { binding.etStaffUsername.setError("Required"); return; }
-        if (!viewModel.isEditing() && password.isEmpty()) {
-            binding.etStaffPassword.setError("Required for new account"); return;
-        }
-        if (!viewModel.isEditing() && password.length() < 6) {
-            binding.etStaffPassword.setError("At least 6 characters"); return;
-        }
-        if (firstName.isEmpty()) { binding.etStaffFirstName.setError("Required"); return; }
-        if (lastName.isEmpty()) { binding.etStaffLastName.setError("Required"); return; }
-        if (email.isEmpty()) { binding.etStaffEmail.setError("Required"); return; }
-        if (phone.isEmpty()) { binding.etStaffPhone.setError("Required"); return; }
-
         EmployeeDTO dto = new EmployeeDTO(
                 username,
                 password.isEmpty() ? null : password,
@@ -117,6 +123,7 @@ public class StaffDetailFragment extends Fragment {
 
         viewModel.saveEmployee(dto).observe(getViewLifecycleOwner(), resource -> {
             if (resource != null) {
+                setLoading(resource.status == Resource.Status.LOADING);
                 if (resource.status == Resource.Status.SUCCESS) {
                     Toast.makeText(getContext(), viewModel.isEditing() ? "Updated successfully" : "Staff account created", Toast.LENGTH_SHORT).show();
                     navigateBack();
@@ -128,12 +135,10 @@ public class StaffDetailFragment extends Fragment {
     }
 
     private void confirmDelete() {
-        new AlertDialog.Builder(requireContext())
+        DialogUtils.showDeleteConfirmDialog(requireContext(), "Staff Account", () ->
-                .setTitle("Delete Staff Account?")
-                .setMessage("This will permanently delete this staff account.")
-                .setPositiveButton("Yes", (d, w) ->
                 viewModel.deleteEmployee().observe(getViewLifecycleOwner(), resource -> {
                     if (resource != null) {
+                        setLoading(resource.status == Resource.Status.LOADING);
                         if (resource.status == Resource.Status.SUCCESS) {
                             navigateBack();
                         } else if (resource.status == Resource.Status.ERROR) {
@@ -141,8 +146,7 @@ public class StaffDetailFragment extends Fragment {
                                     Toast.LENGTH_SHORT).show();
                         }
                     }
-                        }))
+                }));
-                .setNegativeButton("No", null).show();
     }
 
     private void navigateBack() {

android/app/src/main/java/com/example/petstoremobile/fragments/listfragments/detailfragments/SupplierDetailFragment.java

@@ -58,6 +58,12 @@ public class SupplierDetailFragment extends Fragment {
         binding.btnDeleteSupplier.setOnClickListener(v -> deleteSupplier());
     }
 
+    private void setLoading(boolean loading) {
+        if (binding != null && binding.progressBar != null) {
+            binding.progressBar.setVisibility(loading ? View.VISIBLE : View.GONE);
+        }
+    }
+
     @Override
     public void onDestroyView() {
         super.onDestroyView();
@@ -85,6 +91,8 @@ public class SupplierDetailFragment extends Fragment {
         supplierDTO.setSupPhone(phone);
 
         viewModel.saveSupplier(supplierDTO).observe(getViewLifecycleOwner(), resource -> {
+            if (resource == null) return;
+            setLoading(resource.status == Resource.Status.LOADING);
             if (resource.status == Resource.Status.SUCCESS) {
                 if (viewModel.isEditing()) {
                     ActivityLogger.logChange(requireContext(), "Supplier", "UPDATED", (int) viewModel.getSupId());
@@ -103,6 +111,8 @@ public class SupplierDetailFragment extends Fragment {
     private void deleteSupplier() {
         DialogUtils.showDeleteConfirmDialog(requireContext(), "Supplier", () ->
                 viewModel.deleteSupplier().observe(getViewLifecycleOwner(), resource -> {
+                    if (resource == null) return;
+                    setLoading(resource.status == Resource.Status.LOADING);
                     if (resource.status == Resource.Status.SUCCESS) {
                         ActivityLogger.logChange(requireContext(), "Supplier", "DELETED", (int) viewModel.getSupId());
                         Toast.makeText(getContext(), "Supplier deleted successfully!", Toast.LENGTH_SHORT).show();
@@ -138,6 +148,7 @@ public class SupplierDetailFragment extends Fragment {
     private void loadSupplierData() {
         viewModel.loadSupplier().observe(getViewLifecycleOwner(), resource -> {
             if (resource == null) return;
+            setLoading(resource.status == Resource.Status.LOADING);
             if (resource.status == Resource.Status.SUCCESS && resource.data != null) {
                 SupplierDTO s = resource.data;
                 binding.etSupCompany.setText(s.getSupCompany());

android/app/src/main/java/com/example/petstoremobile/fragments/listfragments/listprofilefragments/PetProfileFragment.java

@@ -95,6 +95,12 @@ public class PetProfileFragment extends Fragment {
         return binding.getRoot();
     }
 
+    private void setLoading(boolean loading) {
+        if (binding != null && binding.progressBar != null) {
+            binding.progressBar.setVisibility(loading ? View.VISIBLE : View.GONE);
+        }
+    }
+
     @Override
     public void onDestroyView() {
         super.onDestroyView();
@@ -104,6 +110,7 @@ public class PetProfileFragment extends Fragment {
     private void loadPetData() {
         viewModel.getPetById(petId).observe(getViewLifecycleOwner(), resource -> {
             if (resource == null) return;
+            setLoading(resource.status == Resource.Status.LOADING);
             if (resource.status == Resource.Status.SUCCESS && resource.data != null) {
                 PetDTO pet = resource.data;
                 binding.tvPetName.setText(pet.getPetName());
@@ -172,14 +179,14 @@ public class PetProfileFragment extends Fragment {
             MultipartBody.Part body = MultipartBody.Part.createFormData("image", file.getName(), requestFile);
 
             viewModel.uploadPetImage(petId, body).observe(getViewLifecycleOwner(), resource -> {
-                if (resource != null && resource.status != Resource.Status.LOADING) {
+                if (resource == null) return;
+                setLoading(resource.status == Resource.Status.LOADING);
                 if (resource.status == Resource.Status.SUCCESS) {
                     Toast.makeText(getContext(), "Pet photo updated successfully", Toast.LENGTH_SHORT).show();
                     loadPetImage((int) petId);
-                    } else {
+                } else if (resource.status == Resource.Status.ERROR) {
                     Toast.makeText(getContext(), "Upload failed: " + resource.message, Toast.LENGTH_SHORT).show();
                 }
-                }
             });
         } catch (Exception e) {
             Log.e("UPLOAD_PET_IMAGE", "Error: " + e.getMessage());
@@ -188,15 +195,15 @@ public class PetProfileFragment extends Fragment {
 
     private void deletePetImage() {
         viewModel.deletePetImage(petId).observe(getViewLifecycleOwner(), resource -> {
-            if (resource != null && resource.status != Resource.Status.LOADING) {
+            if (resource == null) return;
+            setLoading(resource.status == Resource.Status.LOADING);
             if (resource.status == Resource.Status.SUCCESS) {
                 Toast.makeText(getContext(), "Pet photo removed", Toast.LENGTH_SHORT).show();
                 hasImage = false;
                 binding.imgPet.setImageResource(R.drawable.placeholder);
-                } else {
+            } else if (resource.status == Resource.Status.ERROR) {
                 Toast.makeText(getContext(), "Delete failed: " + resource.message, Toast.LENGTH_SHORT).show();
             }
-            }
         });
     }
 }

android/app/src/main/java/com/example/petstoremobile/viewmodels/ChatListViewModel.java

@@ -61,12 +61,15 @@ public class ChatListViewModel extends ViewModel {
     }
 
     public void loadCustomers() {
+        isLoading.setValue(true);
         customerRepository.getAllCustomers(0, 100).observeForever(resource -> {
             if (resource != null && resource.status == Resource.Status.SUCCESS && resource.data != null) {
                 for (CustomerDTO c : resource.data.getContent()) {
                     customerNames.put(c.getCustomerId(), c.getFullName());
                 }
                 loadConversations();
+            } else if (resource != null && resource.status == Resource.Status.ERROR) {
+                isLoading.setValue(false);
             }
         });
     }
@@ -96,6 +99,7 @@ public class ChatListViewModel extends ViewModel {
     }
 
     public void loadMessageHistory(Long conversationId) {
+        isLoading.setValue(true);
         chatRepository.getMessages(conversationId).observeForever(resource -> {
             if (resource != null && resource.status == Resource.Status.SUCCESS && resource.data != null) {
                 List<Message> messages = new ArrayList<>();
@@ -103,6 +107,9 @@ public class ChatListViewModel extends ViewModel {
                     messages.add(dtoToModel(dto));
                 }
                 messageList.setValue(messages);
+                isLoading.setValue(false);
+            } else if (resource != null && resource.status == Resource.Status.ERROR) {
+                isLoading.setValue(false);
             }
         });
     }

android/app/src/main/java/com/example/petstoremobile/viewmodels/PetDetailViewModel.java

@@ -27,6 +27,7 @@ public class PetDetailViewModel extends ViewModel {
     private final MutableLiveData<PetDTO> petState = new MutableLiveData<>();
     private final MutableLiveData<List<DropdownDTO>> customerList = new MutableLiveData<>(new ArrayList<>());
     private final MutableLiveData<List<DropdownDTO>> storeList = new MutableLiveData<>(new ArrayList<>());
+    private final MutableLiveData<Boolean> isLoading = new MutableLiveData<>(false);
     
     private long petId = -1;
     private boolean isEditing = false;
@@ -91,4 +92,12 @@ public class PetDetailViewModel extends ViewModel {
     public LiveData<List<DropdownDTO>> getStoreList() {
         return storeList;
     }
+
+    public LiveData<Boolean> getIsLoading() {
+        return isLoading;
+    }
+
+    public void setLoading(boolean loading) {
+        isLoading.setValue(loading);
+    }
 }

android/app/src/main/java/com/example/petstoremobile/viewmodels/SaleDetailViewModel.java

@@ -35,6 +35,7 @@ public class SaleDetailViewModel extends ViewModel {
     private final MutableLiveData<List<DropdownDTO>> customerList = new MutableLiveData<>(new ArrayList<>());
     private final MutableLiveData<List<ProductDTO>> productList = new MutableLiveData<>(new ArrayList<>());
     private final MutableLiveData<List<SaleDTO.SaleItemDTO>> cartItems = new MutableLiveData<>(new ArrayList<>());
+    private final MutableLiveData<Boolean> isLoading = new MutableLiveData<>(false);
 
     @Inject
     public SaleDetailViewModel(SaleRepository saleRepository, StoreRepository storeRepository,
@@ -106,4 +107,12 @@ public class SaleDetailViewModel extends ViewModel {
         }
         return total;
     }
+
+    public LiveData<Boolean> getIsLoading() {
+        return isLoading;
+    }
+
+    public void setLoading(boolean loading) {
+        isLoading.setValue(loading);
+    }
 }

android/app/src/main/res/layout/fragment_adoption_detail.xml

@@ -1,5 +1,9 @@
 <?xml version="1.0" encoding="utf-8"?>
-<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
+<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent">
+
+    <LinearLayout
         android:layout_width="match_parent"
         android:layout_height="match_parent"
         android:orientation="vertical"
@@ -211,4 +215,14 @@
 
         </LinearLayout>
 
-</LinearLayout>
+    </LinearLayout>
+
+    <ProgressBar
+        android:id="@+id/progressBar"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:layout_gravity="center"
+        android:visibility="gone"
+        android:indeterminateTint="@color/accent_coral"/>
+
+</FrameLayout>

android/app/src/main/res/layout/fragment_analytics.xml

@@ -1,5 +1,9 @@
 <?xml version="1.0" encoding="utf-8"?>
-<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
+<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent">
+
+    <LinearLayout
         android:layout_width="match_parent"
         android:layout_height="match_parent"
         android:orientation="vertical"
@@ -315,4 +319,14 @@
 
         </ScrollView>
 
-</LinearLayout>
+    </LinearLayout>
+
+    <ProgressBar
+        android:id="@+id/progressBar"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:layout_gravity="center"
+        android:visibility="gone"
+        android:indeterminateTint="@color/accent_coral"/>
+
+</FrameLayout>

android/app/src/main/res/layout/fragment_appointment_detail.xml

@@ -1,5 +1,9 @@
 <?xml version="1.0" encoding="utf-8"?>
-<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
+<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent">
+
+    <LinearLayout
         android:layout_width="match_parent"
         android:layout_height="match_parent"
         android:orientation="vertical"
@@ -265,4 +269,14 @@
 
         </LinearLayout>
 
-</LinearLayout>
+    </LinearLayout>
+
+    <ProgressBar
+        android:id="@+id/progressBar"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:layout_gravity="center"
+        android:visibility="gone"
+        android:indeterminateTint="@color/accent_coral"/>
+
+</FrameLayout>

android/app/src/main/res/layout/fragment_chat.xml

@@ -6,11 +6,15 @@
     android:layout_width="match_parent"
     android:layout_height="match_parent">
 
+    <RelativeLayout
+        android:layout_width="match_parent"
+        android:layout_height="match_parent"
+        android:background="@color/background_grey">
+
         <LinearLayout
             android:layout_width="match_parent"
             android:layout_height="match_parent"
-        android:orientation="vertical"
+            android:orientation="vertical">
-        android:background="@color/background_grey">
 
             <LinearLayout
                 android:layout_width="match_parent"
@@ -126,6 +130,16 @@
 
         </LinearLayout>
 
+        <ProgressBar
+            android:id="@+id/progressBar"
+            android:layout_width="wrap_content"
+            android:layout_height="wrap_content"
+            android:layout_centerInParent="true"
+            android:visibility="gone"
+            android:indeterminateTint="@color/accent_coral"/>
+
+    </RelativeLayout>
+
     <androidx.core.widget.NestedScrollView
         android:id="@+id/chatListDrawer"
         android:layout_width="260dp"

android/app/src/main/res/layout/fragment_inventory_detail.xml

@@ -1,5 +1,9 @@
 <?xml version="1.0" encoding="utf-8"?>
-<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
+<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent">
+
+    <LinearLayout
         android:layout_width="match_parent"
         android:layout_height="match_parent"
         android:orientation="vertical"
@@ -152,4 +156,14 @@
 
         </LinearLayout>
 
-</LinearLayout>
+    </LinearLayout>
+
+    <ProgressBar
+        android:id="@+id/progressBar"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:layout_gravity="center"
+        android:visibility="gone"
+        android:indeterminateTint="@color/accent_coral"/>
+
+</FrameLayout>

android/app/src/main/res/layout/fragment_pet_detail.xml

@@ -1,5 +1,10 @@
 <?xml version="1.0" encoding="utf-8"?>
-<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
+<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent">
+
+    <LinearLayout
         android:layout_width="match_parent"
         android:layout_height="match_parent"
         android:orientation="vertical"
@@ -226,4 +231,14 @@
 
         </LinearLayout>
 
-</LinearLayout>
+    </LinearLayout>
+
+    <ProgressBar
+        android:id="@+id/progressBar"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:layout_gravity="center"
+        android:visibility="gone"
+        android:indeterminateTint="@color/accent_coral"/>
+
+</FrameLayout>

android/app/src/main/res/layout/fragment_pet_profile.xml

@@ -1,5 +1,9 @@
 <?xml version="1.0" encoding="utf-8"?>
-<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
+<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent">
+
+    <LinearLayout
         android:layout_width="match_parent"
         android:layout_height="match_parent"
         android:orientation="vertical"
@@ -303,4 +307,14 @@
 
         </LinearLayout>
 
-</LinearLayout>
+    </LinearLayout>
+
+    <ProgressBar
+        android:id="@+id/progressBar"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:layout_gravity="center"
+        android:visibility="gone"
+        android:indeterminateTint="@color/accent_coral"/>
+
+</FrameLayout>

android/app/src/main/res/layout/fragment_product_detail.xml

@@ -1,5 +1,9 @@
 <?xml version="1.0" encoding="utf-8"?>
-<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
+<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent">
+
+    <LinearLayout
         android:layout_width="match_parent"
         android:layout_height="match_parent"
         android:orientation="vertical"
@@ -192,4 +196,14 @@
 
         </LinearLayout>
 
-</LinearLayout>
+    </LinearLayout>
+
+    <ProgressBar
+        android:id="@+id/progressBar"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:layout_gravity="center"
+        android:visibility="gone"
+        android:indeterminateTint="@color/accent_coral"/>
+
+</FrameLayout>

android/app/src/main/res/layout/fragment_product_supplier_detail.xml

@@ -1,5 +1,9 @@
 <?xml version="1.0" encoding="utf-8"?>
-<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
+<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent">
+
+    <LinearLayout
         android:layout_width="match_parent"
         android:layout_height="match_parent"
         android:orientation="vertical"
@@ -135,4 +139,14 @@
 
         </LinearLayout>
 
-</LinearLayout>
+    </LinearLayout>
+
+    <ProgressBar
+        android:id="@+id/progressBar"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:layout_gravity="center"
+        android:visibility="gone"
+        android:indeterminateTint="@color/accent_coral"/>
+
+</FrameLayout>

android/app/src/main/res/layout/fragment_profile.xml

@@ -1,5 +1,9 @@
 <?xml version="1.0" encoding="utf-8"?>
-<ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
+<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent">
+
+    <ScrollView
         android:layout_width="match_parent"
         android:layout_height="match_parent"
         android:background="@color/background_grey">
@@ -197,4 +201,14 @@
 
         </LinearLayout>
 
-</ScrollView>
+    </ScrollView>
+
+    <ProgressBar
+        android:id="@+id/progressBar"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:layout_gravity="center"
+        android:visibility="gone"
+        android:indeterminateTint="@color/accent_coral"/>
+
+</FrameLayout>

android/app/src/main/res/layout/fragment_purchase_order_detail.xml

@@ -1,5 +1,9 @@
 <?xml version="1.0" encoding="utf-8"?>
-<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
+<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent">
+
+    <LinearLayout
         android:layout_width="match_parent"
         android:layout_height="match_parent"
         android:orientation="vertical"
@@ -137,4 +141,14 @@
 
         </LinearLayout>
 
-</LinearLayout>
+    </LinearLayout>
+
+    <ProgressBar
+        android:id="@+id/progressBar"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:layout_gravity="center"
+        android:visibility="gone"
+        android:indeterminateTint="@color/accent_coral"/>
+
+</FrameLayout>

android/app/src/main/res/layout/fragment_refund.xml

@@ -1,5 +1,9 @@
 <?xml version="1.0" encoding="utf-8"?>
-<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
+<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent">
+
+    <LinearLayout
         android:layout_width="match_parent"
         android:layout_height="match_parent"
         android:orientation="vertical"
@@ -219,4 +223,14 @@
 
         </LinearLayout>
 
-</LinearLayout>
+    </LinearLayout>
+
+    <ProgressBar
+        android:id="@+id/progressBar"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:layout_gravity="center"
+        android:visibility="gone"
+        android:indeterminateTint="@color/accent_coral"/>
+
+</FrameLayout>

android/app/src/main/res/layout/fragment_sale_detail.xml

@@ -1,5 +1,9 @@
 <?xml version="1.0" encoding="utf-8"?>
-<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
+<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent">
+
+    <LinearLayout
         android:layout_width="match_parent"
         android:layout_height="match_parent"
         android:orientation="vertical"
@@ -330,4 +334,14 @@
 
         </LinearLayout>
 
-</LinearLayout>
+    </LinearLayout>
+
+    <ProgressBar
+        android:id="@+id/progressBar"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:layout_gravity="center"
+        android:visibility="gone"
+        android:indeterminateTint="@color/accent_coral"/>
+
+</FrameLayout>

android/app/src/main/res/layout/fragment_service_detail.xml

@@ -1,5 +1,9 @@
 <?xml version="1.0" encoding="utf-8"?>
-<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
+<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent">
+
+    <LinearLayout
         android:layout_width="match_parent"
         android:layout_height="match_parent"
         android:orientation="vertical"
@@ -168,4 +172,14 @@
 
         </LinearLayout>
 
-</LinearLayout>
+    </LinearLayout>
+
+    <ProgressBar
+        android:id="@+id/progressBar"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:layout_gravity="center"
+        android:visibility="gone"
+        android:indeterminateTint="@color/accent_coral"/>
+
+</FrameLayout>

android/app/src/main/res/layout/fragment_staff_detail.xml

@@ -1,5 +1,9 @@
 <?xml version="1.0" encoding="utf-8"?>
-<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
+<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent">
+
+    <LinearLayout
         android:layout_width="match_parent"
         android:layout_height="match_parent"
         android:orientation="vertical"
@@ -230,4 +234,14 @@
 
         </LinearLayout>
 
-</LinearLayout>
+    </LinearLayout>
+
+    <ProgressBar
+        android:id="@+id/progressBar"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:layout_gravity="center"
+        android:visibility="gone"
+        android:indeterminateTint="@color/accent_coral"/>
+
+</FrameLayout>

android/app/src/main/res/layout/fragment_supplier_detail.xml

@@ -1,5 +1,9 @@
 <?xml version="1.0" encoding="utf-8"?>
-<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
+<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent">
+
+    <LinearLayout
         android:layout_width="match_parent"
         android:layout_height="match_parent"
         android:orientation="vertical"
@@ -179,4 +183,14 @@
 
         </LinearLayout>
 
-</LinearLayout>
+    </LinearLayout>
+
+    <ProgressBar
+        android:id="@+id/progressBar"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:layout_gravity="center"
+        android:visibility="gone"
+        android:indeterminateTint="@color/accent_coral"/>
+
+</FrameLayout>