我试图在 AnimatedList 上预先生成所有更新操作,就像我为 Android 中的 RecyclerView 适配器所做的那样。但是当我要清除所有数据时,我不知道该怎么做。
如果我这样做
setState(() {
_data.clear();
});
那么backing data被清除了但是GlobalKey的当前状态仍然不知道变化,并且上面没有clear()
方法。
补充代码
import 'package:flutter/material.dart';
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
return MaterialApp(
debugShowCheckedModeBanner: false,
home: Scaffold(
appBar: AppBar(title: Text('Update AnimatedList data')),
body: BodyWidget(),
),
);
}
}
class BodyWidget extends StatefulWidget {
@override
BodyWidgetState createState() {
return new BodyWidgetState();
}
}
class BodyWidgetState extends State<BodyWidget> {
// the GlobalKey is needed to animate the list
final GlobalKey<AnimatedListState> _listKey = GlobalKey();
// backing data
List<String> _data = ['Horse', 'Cow', 'Camel', 'Sheep', 'Goat'];
@override
Widget build(BuildContext context) {
return Column(
children: <Widget>[
SizedBox(
height: 400,
child: AnimatedList(
key: _listKey,
initialItemCount: _data.length,
itemBuilder: (context, index, animation) {
return _buildItem(_data[index], animation);
},
),
),
RaisedButton(
child: Text(
'Clear all items',
style: TextStyle(fontSize: 20),
),
onPressed: () {
_clearAllItems();
},
)
],
);
}
Widget _buildItem(String item, Animation animation) {
return SizeTransition(
sizeFactor: animation,
child: Card(
child: ListTile(
title: Text(
item,
style: TextStyle(fontSize: 20),
),
),
),
);
}
void _clearAllItems() {
_data.clear();
// no such method
_listKey.currentState.clear();
}
}
最佳答案
您必须手动删除 _listKey.currentState
中的项目
示例代码:
import 'package:flutter/material.dart';
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
return MaterialApp(
debugShowCheckedModeBanner: false,
home: Scaffold(
appBar: AppBar(title: Text('Update AnimatedList data')),
body: BodyWidget(),
),
);
}
}
class BodyWidget extends StatefulWidget {
@override
BodyWidgetState createState() {
return new BodyWidgetState();
}
}
class BodyWidgetState extends State<BodyWidget> {
// the GlobalKey is needed to animate the list
final GlobalKey<AnimatedListState> _listKey = GlobalKey();
// backing data
List<String> _data = ['Horse', 'Cow', 'Camel', 'Sheep', 'Goat'];
@override
Widget build(BuildContext context) {
return Column(
children: <Widget>[
SizedBox(
height: 400,
child: AnimatedList(
key: _listKey,
initialItemCount: _data.length,
itemBuilder: (context, index, animation) {
return _buildItem(_data[index], animation);
},
),
),
RaisedButton(
child: Text(
'Clear all items',
style: TextStyle(fontSize: 20),
),
onPressed: () {
_clearAllItems();
},
)
],
);
}
Widget _buildItem(String item, Animation animation) {
return SizeTransition(
sizeFactor: animation,
child: Card(
child: ListTile(
title: Text(
item,
style: TextStyle(fontSize: 20),
),
),
),
);
}
void _clearAllItems() {
for (var i = 0; i <= _data.length - 1; i++) {
_listKey.currentState.removeItem(0,
(BuildContext context, Animation<double> animation) {
return Container();
});
}
_data.clear();
}
}
https://stackoverflow.com/questions/54376474/
相关文章:
dart - ListView.builder 在 flutter 中逐项滚动
flutter - Hummingbird(现在是 Flutter for web)计划发布。我应该
android - flutter Assets 错误 : EXCEPTION CAUGHT BY
dart - 如何在继续 flutter 之前等待 future 的对象?
firebase - Flutter 多个 Firestore 查询
flutter - 使用 FadeInImage Flutter 正确拟合图像
dart - Flutter - 关闭小部件时 BLoC 流实例会导致内存泄漏吗?