| name | flutter-performance |
| description | Optimize Flutter widget rebuilds, memory usage, rendering, and scrolling performance. Use when diagnosing jank, reducing rebuilds, or improving list performance—not performance tests, monitoring setup, or API optimization. |
| metadata | {"triggers":{"files":["lib/presentation/**","pubspec.yaml","ListView.builder"],"keywords":["const","buildWhen","Isolate","RepaintBoundary"]}} |
Performance
Priority: P1 (HIGH)
- Rebuilds: Use
const widgets and buildWhen / select for granular updates.
- Lists: Always use
ListView.builder for item recycling.
- Heavy Tasks: Use
compute() or Isolates for parsing/logic.
- Repaints: Use
RepaintBoundary for complex animations. Use debugRepaintRainbowEnabled to debug.
- Images: Use
CachedNetworkImage + memCacheWidth. precachePicture for SVGs.
- Keys: Provide
ValueKey for list items and stable IDs for reconciliation.
- Resource Cleanup: Dispose controllers/streams in
dispose().
- Pagination: Default to 20 items per page for network lists.
- Build Purity: Keep
build methods free of heavy work; move logic to BLoC/Application.
- Image Resizing: Always set
maxWidth/maxHeight when loading images.
Anti-Patterns
- No Root
setState(): Use BlocBuilder with buildWhen or context.select() for granular updates
- No Heavy Business in
build(): Move sorting/filtering/heavy logic to BLoC or compute()
- No Non-
const Leaf Nodes: Apply const to all static widgets to skip unnecessary reconciliation
- No Large
Column Lists: Use ListView.builder for efficient item recycling in large lists
BlocBuilder<UserBloc, UserState>(
buildWhen: (p, c) => p.id != c.id,
builder: (context, state) => Text(state.name),
)
