如何检查按钮是否被按下答案

【问题标题】：How to check if a button is pressed如何检查按钮是否被按下
【发布时间】：2020-01-02 14:44:49
【问题描述】：

我需要一个点赞按钮，点击一次会增加点赞数，第二次点击会减少点赞数，如何判断按钮是否被点击

这是我的客户颤振小部件练习

按钮小部件

lass ButtonBuilder extends StatefulWidget{
  final Icon icon;

  ButtonBuilder({this.icon,});

  _ButtonBuilderState createState()=>_ButtonBuilderState(this.icon);
}

class _ButtonBuilderState extends State<ButtonBuilder>{
  final Icon _icon;

   _ButtonBuilderState(this._icon);

  final _bloc=ButtonCounterBloc();

  @override
  Widget build(BuildContext context) {
    return RootButton(
      child: StreamBuilder(
        stream: _bloc.counter,
        initialData: 0,
        builder: (BuildContext context,AsyncSnapshot snapshot){
          return _buildButton(_icon,'${snapshot.data}');
        },
      ),
    );
  }

  _buildButton(Icon _icon,String _text){
    return Column(
      children: <Widget>[
        IconButton(
          icon: _icon,
          onPressed: ()=>_bloc.buttonEventSink.add(FirstOnPressedEvent()),
        ),
        Text(_text),
      ],
    );
  }
}

main.dart

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);

  final String title;

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Center(
        child: Row(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            ButtonBuilder(icon: Icon(Icons.thumb_up),),
            ButtonBuilder(icon: Icon(Icons.thumb_down),),
          ],
        ),
      ),
    );
  }
}

我不知道如何检查按钮是否被点击

【问题讨论】：

简单地使用一个布尔变量initialy一旦按下使其为真再次按下时检查它是否已经为真然后将其设为假

标签： android ios flutter dart bloc

【解决方案1】：

您可以将名为 isPressed 的标志最初设置为 false，每次按下按钮时都会取消该标志。

而在onPressed回调中，你可以根据变量编写不同的逻辑。

但您应该记住，在下面的示例中，一旦按钮宽度的 State 被释放，_isPressed 变量将被重置。

如果您希望有一个持久按钮，您可以在ButtonCounterBloc 中添加一个类似的参数，并将其值分配给initState 类的initState 方法中的_isPressed。

这样，即使应用重新启动或状态被释放并再次挂载，您的按钮也会保持不变。

class ButtonBuilder extends StatefulWidget{
  final Icon icon;

  ButtonBuilder({this.icon,});

  _ButtonBuilderState createState()=>_ButtonBuilderState(this.icon);
}

class _ButtonBuilderState extends State<ButtonBuilder>{
  final Icon _icon;

   _ButtonBuilderState(this._icon);

  final _bloc=ButtonCounterBloc();
  bool _isPressed = false;

  @override
  Widget build(BuildContext context) {
    return RootButton(
      child: StreamBuilder(
        stream: _bloc.counter,
        initialData: 0,
        builder: (BuildContext context,AsyncSnapshot snapshot){
          return _buildButton(_icon,'${snapshot.data}');
        },
      ),
    );
  }

  _buildButton(Icon _icon,String _text){
    return Column(
      children: <Widget>[
        IconButton(
          icon: _icon,
          onPressed: () {
            setState(() {
              _isPressed = !_isPressed;
            });
            if(_isPressed) {
              // This block will be executed when button is pressed odd number of times.
              _bloc.buttonEventSink.add(FirstOnPressedEvent());
            } else {
              // This block will be executed when button is pressed even number of times;
            }
          }
        ),
        Text(_text),
      ],
    );
  }
}

【讨论】：