Flutter Performance

Flutter Performance

Commands

flutter run --profile  # Required for profiling
flutter pub global run devtools

Targets

Widget Optimization

Const Constructors

// GOOD
const Column(children: [Text('Static'), Icon(Icons.star)])

Extract Widgets

// GOOD: Only counter rebuilds
Column(
  children: [
    const ExpensiveWidget(),  // no rebuild
    _Counter(),               // isolated state
  ],
)

RepaintBoundary

RepaintBoundary(child: AnimatedWidget())

Build Optimization

// BAD: compute in build
final sorted = items..sort();

// GOOD: compute once
late List<Item> _sorted;
void initState() { _sorted = items..sort(); }

Memory Management

@override
void dispose() {
  _animController.dispose();
  _textController.dispose();
  _subscription?.cancel();
  super.dispose();
}

// Check mounted
if (!mounted) return;
setState(() => _data = data);

Lists

// Use builder
ListView.builder(itemCount: items.length, itemBuilder: ...)

// Fixed extent
ListView.builder(itemExtent: 72, ...)

// Keys
ValueKey(item.id)

Images

CachedNetworkImage(
  imageUrl: url,
  memCacheWidth: 200,
  memCacheHeight: 200,
)

Checklist

• Profiled in profile mode
• No expensive ops in build()
• Const constructors used
• ListView.builder for lists
• Controllers disposed
• Check mounted before setState

Related Skills

• flutter-animations: Animation performance
• flutter-code-quality: Static analysis