[英]Delete specific widget | Flutter & Riverpod
如图所示,我试图有一个骰子列表,我可以在其中添加或删除骰子。 我尝试过 StateProvider、ChangeNotifier 和 StateNotifier。 每一个似乎都没有像我期望的那样工作。 我正在尝试创建一个包含 dieWidgets 列表的提供程序,但是当我长按它时,我无法弄清楚如何删除特定的 die。 图像显示了一个删除它的弹出菜单,这是长期目标,但现在只需长按删除就可以了。 关于如何解决这个问题的想法?
main.dart
class DiceNotifier extends ChangeNotifier {
List<DieWidget> dice = [];
void add() {
dice.add(DieWidget());
notifyListeners();
}
void removeDie(int id) {
// FIXME: Unable to delete a die based on id
print(id);
notifyListeners();
}
}
final diceProvider = ChangeNotifierProvider((_) {
return DiceNotifier();
});
class MyHomePage extends ConsumerWidget {
@override
Widget build(BuildContext context, ScopedReader watch) {
final dice = watch(diceProvider).dice;
return Scaffold(
appBar: AppBar(
title: Text("Dice"),
),
body: Center(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
...dice,
],
),
),
floatingActionButton: FloatingActionButton(
onPressed: () {
context.read(diceProvider).add();
},
child: Icon(Icons.add),
), // This trailing comma makes auto-formatting nicer for build methods.
);
}
}
die_widget.dart
class DieWidget extends StatefulWidget {
@override
_DieWidgetState createState() => _DieWidgetState();
}
class _DieWidgetState extends State<DieWidget> {
int value = 0;
int id = 0;
@override
Widget build(BuildContext context) {
return FlatButton(
child: Text(
'$value',
),
onPressed: () {
setState(() {
value++;
id++;
});
// context.read(dieProvider).increment();
},
onLongPress: () {
final dice = context.read(diceProvider);
dice.removeDie(id);
// print(this.value);
},
);
}
}
一种解决方案是在DiceWidget
class 中定义一个参数value
:
class DiceWidget extends StatefulWidget {
const DiceWidget({ Key key, this.value }) : super(key: key);
int value;
@override
_DiceWidgetState createState() => _DiceWidgetState();
}
并从DiceWidget
访问这些数据:
class DiceWidget extends StatefulWidget {
@override
_DiceWidgetState createState() => _DiceWidgetState();
}
class _DiceWidgetState extends State<DiceWidget> {
@override
Widget build(BuildContext context) {
return FlatButton(
child: Text(
widget.value.toString() ?? '',
),
onLongPress: () {
final dice = context.read(diceProvider);
dice.removeDice(widget.value);
// print(widget.value);
},
);
}
}
在DiceNotifier
class 中,我建议将dices
数组实现为List<int>
:
List<int> dices = [];
因此, addDice()
和removeDice()
函数将分别为:
class DiceNotifier extends ChangeNotifier {
List<int> dices = [];
void addDice() {
dices.add(dices.length);
notifyListeners();
}
void removeDice(int id) {
dices.remove(id);
print(id);
notifyListeners();
}
}
为了使示例工作,我们还需要修改MyHomePage
Column
以构建children
DiceWidget
:
...dices.map((d) => DiceWidget(value: d)).toList(),
整个示例将是: main.dart
:
class DiceNotifier extends ChangeNotifier {
List<int> dices = [];
void addDice() {
dices.add(dices.length);
notifyListeners();
}
void removeDice(int id) {
dices.remove(id);
print(id);
notifyListeners();
}
}
final diceProvider = ChangeNotifierProvider((_) {
return DiceNotifier();
});
class MyHomePage extends ConsumerWidget {
@override
Widget build(BuildContext context, ScopedReader watch) {
final dices = watch(diceProvider).dices;
return Scaffold(
appBar: AppBar(
title: Text("Dice"),
),
body: Center(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
...dices.map((d) => DiceWidget(value: d)).toList(),
],
),
),
floatingActionButton: FloatingActionButton(
onPressed: () {
context.read(diceProvider).addDice();
},
child: Icon(Icons.add),
),
);
}
}
dice_widget.dart
:
class DiceWidget extends StatefulWidget {
@override
_DiceWidgetState createState() => _DiceWidgetState();
}
class _DiceWidgetState extends State<DiceWidget> {
@override
Widget build(BuildContext context) {
return FlatButton(
child: Text(
widget.value.toString() ?? '',
),
onLongPress: () {
final dice = context.read(diceProvider);
dice.removeDice(widget.value);
print(widget.value);
},
);
}
}
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