1. hook
需要继承HookWidget
useMemoized
useRef useCallback 通过内部使用useMemoized 只调用一次
1.1 属性 行为 组合成了状态，除了状态还有作用
1.2 keys
指定是否应重用 [HookState] 或应创建新的对象列表。创建新的 [Hook] 时，框架会使用
[Hook.shouldPreserveState] 检查键是否匹配。如果没有，之前创建的 [HookState] 将被释放，并使用 [Hook.createState] 创建一个新的，然后是 [HookState.initHook]
2. useMemoized
缓存复杂对象的实例。
useMemoized->_MemoizedHook->_MemoizedHookState-> late final T value = hook.valueBuilder()
build 返回的一直都是value, 需要手动调用
一般useFuture useMemoized 配合使用
3. useCallback
缓存函数对象的实例
4. useRef
创建一个包含单个可变属性的对象。改变对象的属性是无效的。这对于在“构建”调用之间共享状态非常有用，而不会导致不必要的重构。
5. useEffect
对于需要取消的
useEffect->_EffectHook->_EffectHookState->initHook()->disposer = hook.effect()->dispose() => disposer?.call()
会在第一次build的时候主动调用，无需手动调用
dispose
6.1 其他钩子
useValueNotifier
useListenable->_ListenableHook->_ListenableStateHook->_listener->setState
useValueListenable->_UseValueListenableHook->_ListenableHook->
useValueListenable比useListenable多加了一个方法，有了返回值
useListenable相当于ValueListenableBuilder->_valueChanged->setState
useListenableSelector 多了一个条件，如果两个值不一样的时候才build
useAnimationController
useAnimation 相当于AnimatedBuilder->_handleChange->setState
useStreamController
useStream 相当于StreamBuilder
useFuture 相当于FutureBuilder
useReducer state一个是对象， action一个是参数
通过dispatch发送参数来返回新的state
6.2 useXXXX 自定义钩子
7. riverpod
runApp(const ProviderScope(child: App()));
需要继承ConsumerWidget 使用WidgetRef ref
继承 StateNotifier ChangeNotifier
ChangeNotifierProvider StateNotifierProvider
ref.watch 观察刷新
ref.read 修改
ref.listen 监听
8. 常用Provider
FutureProvider
StreamProvider.family可以传入参数
FutureProvider.autoDispose
StateNotifierProvider
StateController
Provider
9. 局部刷新
ValueListenableBuilder
ValueNotifier
Listenable
10. Consumer使用 ，局部刷新
提供程序更新时重建尽可能少的小部件
class Example extends StatefulWidget { @override _ExampleState createState() => _ExampleState(); } class _ExampleState extends State<Example> { @override Widget build(BuildContext context) { return Consumer( builder: (context, ref, child) { final value = ref.watch(helloWorldProvider); return Text(value); // Hello world }, ); } }
11. HookBuilder使用 ，局部刷新
HookBuilder(builder: (BuildContext context){ final num = useState(8); print("HookBuilder-build"); return TextButton( onPressed: () { num.value++; }, child: Text("num=${num.value}")); })
12 . hook源码分析
Hook
- HookWidget vs StatefulWidget
- HookElement vs StatefulElement
- HookState vs State
abstract class Hook<R> with Diagnosticable { final List<Object?>? keys; static R use<R>(Hook<R> hook) { return HookElement._currentHookElement!._use(hook); } static bool shouldPreserveState(Hook<Object?> hook1, Hook<Object?> hook2) {} @protected HookState<R, Hook<R>> createState(); }
1. HookWidget vs StatefulWidget
abstract class HookWidget extends StatelessWidget { /// Initializes [key] for subclasses. const HookWidget({Key? key}) : super(key: key); @override _StatelessHookElement createElement() => _StatelessHookElement(this); } abstract class StatefulWidget extends Widget { const StatefulWidget({ super.key }); @override StatefulElement createElement() => StatefulElement(this); State createState(); }
2. StatefulElement vs HookElement
/// class StatefulElement extends ComponentElement { StatefulElement():_state = createState(){ _state.element = this; _state.widget = widget; } _firstBuild(){ _state.initState(); _state.didChangeDependencies()； rebuild();///performRebuild(); } _update(){ _state.didUpdateWidget(); rebuild(); } build()=>_state.build(this); performRebuild(){ state.didChangeDependencies(); } activate(){ _state.activate(); } deactivete(){ _state.deactivate(): } unamount(){ _state.dispose(); } } class _StatelessHookElement extends StatelessElement with HookElement { _StatelessHookElement(HookWidget hooks) : super(hooks); }
HookElement
- 一个hookElement中有多个Hook，每个hook对应一个hookstate
- 可以根据keys，hookstate不变，但是hook重新赋值 和State对weidget(key,runtype)是一样的
mixin HookElement on ComponentElement { static HookElement? _currentHookElement; _Entry<HookState<Object?, Hook<Object?>>>? _currentHookState; ///一个HookElement对应多个HookState final _hooks = LinkedList<_Entry<HookState<Object?, Hook<Object?>>>>(); final _shouldRebuildQueue = LinkedList<_Entry<bool Function()>>(); LinkedList<_Entry<HookState<Object?, Hook<Object?>>>>? _needDispose; bool? _isOptionalRebuild = false; Widget? _buildCache; Widget build() { final mustRebuild = _isOptionalRebuild != true || _shouldRebuildQueue.any((cb) => cb.value()); _isOptionalRebuild = null; _shouldRebuildQueue.clear(); if (!mustRebuild) { return _buildCache!; } _currentHookState = _hooks.isEmpty ? null : _hooks.first; HookElement._currentHookElement = this; return _buildCache; } R _use<R>(Hook<R> hook) { ///如果为空应为列表中为空 直接添加 if (_currentHookState == null) { _appendHook(hook); }else if(hook.runtimeType != _currentHookState!.value.hook.runtimeType){ /// 是一个新的hook _appendHook(hook); }else if (hook != _currentHookState!.value.hook) { final previousHook = _currentHookState!.value.hook; if (Hook.shouldPreserveState(previousHook, hook)) { ///说明keys不一样了 需要重新hook _currentHookState!.value .._hook = hook ..didUpdateHook(previousHook); } else { ///新创建一个State _needDispose ??= LinkedList(); _needDispose!.add(_Entry(_currentHookState!.value)); _currentHookState!.value = _createHookState<R>(hook); } } final result = _currentHookState!.value.build(this) as R; _currentHookState = _currentHookState!.next; return result; } }
3. HookState vs State
///State bool get mounted => _element != null; ///HookState void markMayNeedRebuild() { if (_element!._isOptionalRebuild != false) { _element! .._isOptionalRebuild = true .._shouldRebuildQueue.add(_Entry(shouldRebuild)) ..markNeedsBuild(); } assert(_element!.dirty, 'Bad state'); }
