# 10. Pagination & List Performance

meta:
  id: android-production-10
  feature: android-production
  priority: P2
  depends_on: []
  tags: [performance, lists, production]

objective:
- Implement pagination and optimize list performance to prevent ANRs and jank on large datasets

deliverables:
- Pagination for all list endpoints
- LazyColumn optimization
- DiffUtil or Compose lazy list optimization
- ANR prevention

steps:
1. Implement pagination:
   - Add pagination to tRPC list endpoints (if not already)
   - Use Paging 3 library for Jetpack Compose
   - Configure page size (20-50 items)
   - Add pagination parameters to API calls
2. Optimize LazyColumn:
   - Use key parameter for item stability
   - Use contentType for different item types
   - Avoid unnecessary recompositions
   - Use remember for expensive calculations
3. Add loading states:
   - Skeleton placeholders while loading first page
   - Load more indicator at bottom
   - Empty state for no data
   - Error state with retry
4. Optimize data flow:
   - Use Flow/PagingData in ViewModels
   - CollectAsStateWithLifecycle for Compose
   - Avoid collecting flows in composables directly
5. Prevent ANRs:
   - Move heavy calculations to background threads
   - Use viewModelScope for coroutines
   - Avoid blocking main thread
   - Profile with Android Profiler
6. Add tests:
   - Test pagination boundaries
   - Test scroll performance
   - Test memory usage with large lists

tests:
- Unit: Test pagination logic
- Performance: Scroll test with 1000+ items
- ANR: Profile main thread during list operations

acceptance_criteria:
- All lists paginated (20-50 items per page)
- Paging 3 library used for Compose integration
- LazyColumn with key and contentType optimization
- Skeleton placeholders on initial load
- Load more indicator on scroll
- Empty and error states handled
- No ANRs during list operations
- 60fps scrolling on lists >100 items
- Memory stable during list scrolling
- Unit tests for pagination logic

validation:
- Scroll through alert list → smooth 60fps
- Scroll to bottom → next page loads automatically
- Check Android Profiler → no main thread blocking
- Memory monitor → stable during scrolling
- Test with 1000 items → no ANR, no OOM

notes:
- Paging 3 is the modern standard for Android pagination
- ANRs on lists are often caused by blocking main thread
- Use LazyColumn, not Column, for long lists
- Test on low-end devices (Android 10, 2GB RAM)