Kordant/tasks/android-production/10-pagination-lists.md

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)