Flutter Callback 示例代码

App主体，因为只是做示例，没有做页面变化的效果，所以使用了StatelessWidget这个类

class myApp extends StatelessWidget {

  String actionName;
  //declare & create object
  Lee classLee = new Lee();
  //create string only array
  List<String> actions = ['First Button Click','Second Button Click','Third Button Click'];

  void onPressFirstBtn(){
    classLee.action_name = actions[0];
    classLee.action();
  }
  void onPressSecondBtn(){
    classLee.action_name = actions[1];
    classLee.action();
  }
  void onPressThirdBtn(){
    classLee.action_name = actions[2];
    classLee.action();
  }

  @override
  Widget build(BuildContext context) {
    // TODO: implement build
    return new Scaffold(
      appBar: AppBar(
        title: Text('Bar Title'),
      ),
      body: Center(
        child: Column(
          children: <Widget>[
            new MyButton(
              onPress: onPressFirstBtn,
              title: Text('First_Btn'),
              icon: Icon(Icons.favorite),
            ),
            new MyButton(
              onPress: onPressSecondBtn,
              title: Text('Second_Btn'),
              icon: Icon(Icons.favorite),
            ),
            new MyButton(
              onPress: onPressThirdBtn,
              title: Text('third_Btn'),
              icon: Icon(Icons.favorite),
            )
          ],
        ),
      ),
    );
  }
}

按钮，其中声明了回调函数onPress，并将其与其它属性放入该类的构造方法中

class MyButton extends StatelessWidget {

  //callback
  @required VoidCallback onPress;
  Text title;
  Icon icon;
  //constructor
  MyButton({this.onPress,this.title,this.icon});
  
  @override
  Widget build(BuildContext context) {
    // TODO: implement build
    return new Container(
      child: new Column(
        mainAxisAlignment: MainAxisAlignment.center,
        children: <Widget>[
          new FlatButton(
            onPressed: onPress,//这里为回调函数的使用，即每次按钮触发点击事件则调用回调函数
            color: Colors.pink[100],
            child: new Column(
              children: <Widget>[
                this.title,
                this.icon
              ],
            ),
          ),
        ],
      ),
    );
  }
}

最后这个类为测试使用，不同的按钮点击会log出不同的actionName

class Lee{
  String action_name;
  Lee({this.action_name});

  void action() {
    print('$action_name');
  }
}