如何从Dart / Flutter中自己的回调（onPressed）中访问Widget

3 回答

• 2

  您可以将某些属性变为变量 . 然后，您可以在 onPressed() 中调用 setState() 来更改属性变量 .
  此示例显示如何使用此方法更改按钮的文本颜色：

  Color textColor = Colors.white;
    @override
    Widget build(BuildContext context) {
      return new Container(
        height: 72.0, // in logical pixels
        padding: const EdgeInsets.symmetric(horizontal: 8.0, vertical: 8.0),
        decoration: new BoxDecoration(color: Colors.white),
        // Row is a horizontal, linear layout.
        child: new MaterialButton(
          child: new Text(
            _sprinkler.name,
            style: new TextStyle(color: textColor)
            ),
          splashColor: Colors.blueAccent,
          color: Colors.blue[800],
          onPressed: () {
            this.setState(() {
              textColor = Colors.red;
            })
          },
        ),
      );
    }
  

  回复于 2024-04-29T14:29:24+08:00
• 2

  您可能想要使用StatefulWidget，如下所示：

  class MyWidget extends StatefulWidget {
    _MyWidgetState createState() => new _MyWidgetState();
  }
  class _MyWidgetState extends State<MyWidget> {
    Color c = Colors.blue.shade500;
  
    Widget build() => new MaterialButton(
      color: c,
      onPressed: () => setState(() {
        c = Colors.red.shade500;
      }),
    );
  }
  

  回复于 2024-04-29T14:29:24+08:00
• 3

  感谢您的意见 . 正确的解决方案是你推荐的，看起来像这样：

  class SprinklerListItem extends StatefulWidget {
    // This class is the configuration for the state. It holds the
    // values (in this nothing) provided by the parent and used by the build
    // method of the State. Fields in a Widget subclass are always marked "final".
    final Sprinkler _sprinkler;
    SprinklerListItem(this._sprinkler);
  
  
    @override
    _SprinklerListItemState createState() {
      return new _SprinklerListItemState(this._sprinkler);
    }
  }
  
  
  class _SprinklerListItemState extends State<SprinklerListItem> {
    final Sprinkler _sprinkler;
  
    _SprinklerListItemState(this._sprinkler);
  
    Color textColor = Colors.white;
    Color bgColor = Colors.blue[800];
    @override
    Widget build(BuildContext context) {
      return new Container(
        height: 72.0, // in logical pixels
        padding: const EdgeInsets.symmetric(horizontal: 8.0, vertical: 8.0),
        decoration: new BoxDecoration(color: Colors.white),
        // Row is a horizontal, linear layout.
        child: new MaterialButton(
          child: new Text(
            _sprinkler.name,
            style: new TextStyle(color: textColor)
            ),
          splashColor: Colors.blueAccent,
          color: bgColor,
          onPressed: () {
            this.setState(() {
              textColor = Colors.grey;
              bgColor = Colors.red;
            });
          },
        ),
      );
    }
  }
  

  回复于 2024-04-29T14:29:24+08:00