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