状态管理
InheritedWidget
// 爷爷组件
class StateManagementDemo extends StatefulWidget {
@override
_StateManagementDemoState createState() => _StateManagementDemoState();
}class _StateManagementDemoState extends State {
int _count = 0;
void _transform() {
setState(() {
_count += 1;
});
}@override
Widget build(BuildContext context) {
return CounterProvider(
count: _count,
transform: _transform,
child: Scaffold(
appBar: AppBar(
title: Text('StateManagementDemo'),
elevation: 0,
),
body: CounterWrapper()),
);
}
}
// 父亲组件
class CounterWrapper extends StatelessWidget {
@override
Widget build(BuildContext context) {
return Counter();
}
}
// 孙组件
class Counter extends StatelessWidget {
@override
Widget build(BuildContext context) {
final int count = CounterProvider.of(context).count;
final VoidCallback transform = CounterProvider.of(context).transform;
return Center(
child: ActionChip(label: Text('$count'), onPressed: transform),
);
}
}
// 状态管理组件
class CounterProvider extends InheritedWidget {
final int count;
final VoidCallback transform;
final Widget child;
CounterProvider({this.count, this.transform, this.child}) : super(child: child);
static CounterProvider of(BuildContext context) => context.inheritFromWidgetOfExactType(CounterProvider);
@override
bool updateShouldNotify(InheritedWidget oldWidget) {
return true;
}
}
ScopedModel（第三方库）
// 爷爷组件
class StateManagementDemo extends StatelessWidget {
@override
Widget build(BuildContext context) {
return ScopedModel(
model: CounterModel(),
child: Scaffold(
appBar: AppBar(
title: Text('StateManagementDemo'),
elevation: 0,
),
body: CounterWrapper(),
floatingActionButton: ScopedModelDescendant(
rebuildOnChange: false,
builder: (context, _, model) => FloatingActionButton(
child: Icon(Icons.add),
onPressed: model.transform
),
),
),
);
}
}
// 父亲组件
class CounterWrapper extends StatelessWidget {
@override
Widget build(BuildContext context) {
return Counter();
}
}
// 孙组件
class Counter extends StatelessWidget {
@override
Widget build(BuildContext context) {
return ScopedModelDescendant(
builder: (context, _, model)=>ActionChip(
label: Text('${model.count}'),
onPressed: model.transform,
),
);
}
}
// 状态管理组件
class CounterModel extends Model {
int _count = 0;
int get count => _count;
void transform() {
_count += 1;
notifyListeners();
}
}
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