Performance Optimization
Profiling Commands
# Run in profile mode
flutter run --profile
# Analyze performance
flutter analyze
# DevTools
flutter pub global activate devtools
flutter pub global run devtools
Common Optimizations
Const Widgets
// ❌ Rebuilds every time
Widget build(BuildContext context) {
return Container(
padding: EdgeInsets.all(16), // Creates new object
child: Text('Hello'),
);
}
// ✅ Const prevents rebuilds
Widget build(BuildContext context) {
return Container(
padding: const EdgeInsets.all(16),
child: const Text('Hello'),
);
}
Selective Provider Watching
// ❌ Rebuilds on any user change
final user = ref.watch(userProvider);
return Text(user.name);
// ✅ Only rebuilds when name changes
final name = ref.watch(userProvider.select((u) => u.name));
return Text(name);
RepaintBoundary
// Isolate expensive widgets
RepaintBoundary(
child: ComplexAnimatedWidget(),
)
Image Optimization
// Use cached_network_image
CachedNetworkImage(
imageUrl: url,
placeholder: (_, __) => const CircularProgressIndicator(),
errorWidget: (_, __, ___) => const Icon(Icons.error),
)
// Resize images
Image.network(
url,
cacheWidth: 200, // Resize in memory
cacheHeight: 200,
)
Compute for Heavy Operations
// ❌ Blocks UI thread
final result = heavyComputation(data);
// ✅ Runs in isolate
final result = await compute(heavyComputation, data);
Performance Checklist
| Check |
Solution |
| Unnecessary rebuilds |
Add const, use select() |
| Large lists |
Use ListView.builder |
| Image loading |
Use cached_network_image |
| Heavy computation |
Use compute() |
| Jank in animations |
Use RepaintBoundary |
| Memory leaks |
Dispose controllers |
DevTools Metrics
- Frame rendering time: < 16ms for 60fps
- Widget rebuilds: Minimize unnecessary rebuilds
- Memory usage: Watch for leaks
- CPU profiler: Identify bottlenecks
