1# Performance Optimization
2 
3## Profiling Commands
4 
5```bash
6# Run in profile mode
7flutter run --profile
8 
9# Analyze performance
10flutter analyze
11 
12# DevTools
13flutter pub global activate devtools
14flutter pub global run devtools
15```
16 
17## Common Optimizations
18 
19### Const Widgets
20```dart
21// ❌ Rebuilds every time
22Widget build(BuildContext context) {
23  return Container(
24    padding: EdgeInsets.all(16),  // Creates new object
25    child: Text('Hello'),
26  );
27}
28 
29// ✅ Const prevents rebuilds
30Widget build(BuildContext context) {
31  return Container(
32    padding: const EdgeInsets.all(16),
33    child: const Text('Hello'),
34  );
35}
36```
37 
38### Selective Provider Watching
39```dart
40// ❌ Rebuilds on any user change
41final user = ref.watch(userProvider);
42return Text(user.name);
43 
44// ✅ Only rebuilds when name changes
45final name = ref.watch(userProvider.select((u) => u.name));
46return Text(name);
47```
48 
49### RepaintBoundary
50```dart
51// Isolate expensive widgets
52RepaintBoundary(
53  child: ComplexAnimatedWidget(),
54)
55```
56 
57### Image Optimization
58```dart
59// Use cached_network_image
60CachedNetworkImage(
61  imageUrl: url,
62  placeholder: (_, __) => const CircularProgressIndicator(),
63  errorWidget: (_, __, ___) => const Icon(Icons.error),
64)
65 
66// Resize images
67Image.network(
68  url,
69  cacheWidth: 200,  // Resize in memory
70  cacheHeight: 200,
71)
72```
73 
74### Compute for Heavy Operations
75```dart
76// ❌ Blocks UI thread
77final result = heavyComputation(data);
78 
79// ✅ Runs in isolate
80final result = await compute(heavyComputation, data);
81```
82 
83## Performance Checklist
84 
85| Check | Solution |
86|-------|----------|
87| Unnecessary rebuilds | Add `const`, use `select()` |
88| Large lists | Use `ListView.builder` |
89| Image loading | Use `cached_network_image` |
90| Heavy computation | Use `compute()` |
91| Jank in animations | Use `RepaintBoundary` |
92| Memory leaks | Dispose controllers |
93 
94## DevTools Metrics
95 
96- **Frame rendering time**: < 16ms for 60fps
97- **Widget rebuilds**: Minimize unnecessary rebuilds
98- **Memory usage**: Watch for leaks
99- **CPU profiler**: Identify bottlenecks
100