英文:
why setState not working for List of widgets in flutter
问题
我是Flutter新手，尝试使用Widget列表进行实验。我尝试在Widget列表内部更改状态，即在`initState`中初始化。我创建了一个示例来说明我的目标。
```dart
class Testing extends StatefulWidget {
const Testing({super.key});
@override
State<Testing> createState() => _TestingState();
}
class _TestingState extends State<Testing> {
bool isChanged = false;
List<Widget> simpleWidget = [];
@override
void initState() {
simpleWidget = [_someComplexWidget(), _someComplexWidget()];
super.initState();
}
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title:const Text("Test"),
),
body: Center(
child: Column(
children: [
Container(
child: Column(
children: simpleWidget,
),
),
ElevatedButton(
onPressed: () {
setState(() {
isChanged = !isChanged;
});
},
child: const Text("Click"))
],
),
),
);
}
Widget _someComplexWidget() {
return Text(
"Hello",
style: TextStyle(color: isChanged ? Colors.red : Colors.blue),
);
}
}
我也尝试使用了key，但在这个示例代码中没有起作用。何时使用Keys
这个代码不起作用的原因是什么。
英文:
I am new in flutter I try to experiment with List of Widget . I try to change state inside the list of widget i.e. initialized in initState . I create sample example to what I want to achieve.
class Testing extends StatefulWidget {
const Testing({super.key});
@override
State<Testing> createState() => _TestingState();
}
class _TestingState extends State<Testing> {
bool isChanged = false;
List<Widget> simpleWidget = [];
@override
void initState() {
simpleWidget = [_someComplexWidget(), _someComplexWidget()];
super.initState();
}
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title:const Text("Test"),
),
body: Center(
child: Column(
children: [
Container(
child: Column(
children: simpleWidget,
),
),
ElevatedButton(
onPressed: () {
setState(() {
isChanged = !isChanged;
});
},
child: const Text("Click"))
],
),
),
);
}
Widget _someComplexWidget() {
return Text(
"Hello",
style: TextStyle(color: isChanged ? Colors.red : Colors.blue),
);
}
}
I also try with keys but it did not work in this sample code. When to Use Keys
What is the reason behind not working this code.
答案1
得分: 1
因为你的simpleWidget是在initState中创建的，它在重建时不会改变。
你应该在build方法中添加[_someComplexWidget(), _someComplexWidget()]，以便根据当前状态动态更改它。
class Testing extends StatefulWidget {
const Testing({Key? key});
@override
State<Testing> createState() => _TestingState();
}
class _TestingState extends State<Testing> {
bool isChanged = false;
@override
void initState() {
super.initState();
}
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: const Text("Test"),
),
body: Center(
child: Column(
children: [
Container(
child: Column(
children: [_someComplexWidget(), _someComplexWidget()], // 在这里
),
),
ElevatedButton(
onPressed: () {
setState(() {
isChanged = !isChanged;
});
print(isChanged);
},
child: const Text("Click"),
),
],
),
),
);
}
Widget _someComplexWidget() {
return Text(
"Hello",
style: TextStyle(color: isChanged ? Colors.red : Colors.blue),
);
}
}
英文:
Because your simpleWidget is created at initState & it will not change on rebuild.
You should add [_someComplexWidget(), _someComplexWidget()] under build for it to change dynamically based on the current state.
class Testing extends StatefulWidget {
const Testing({super.key});
@override
State<Testing> createState() => _TestingState();
}
class _TestingState extends State<Testing> {
bool isChanged = false;
@override
void initState() {
super.initState();
}
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: const Text("Test"),
),
body: Center(
child: Column(
children: [
Container(
child: Column(
children: [_someComplexWidget(), _someComplexWidget()], // HERE
),
),
ElevatedButton(
onPressed: () {
setState(() {
isChanged = !isChanged;
});
print(isChanged);
},
child: const Text("Click"))
],
),
),
);
}
Widget _someComplexWidget() {
return Text(
"Hello",
style: TextStyle(color: isChanged ? Colors.red : Colors.blue),
);
}
}
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