dart - 将方法作为参数传递给小部件

Question

我有一个自定义按钮小部件:

class Button extends StatelessWidget {
  final String text;

  Button(this.text);

  @override
  Widget build(BuildContext context) {
    return Container(
      height: 50,
      child: SizedBox(
        width: double.infinity,
        child: RaisedButton(
          onPressed: () => {}, // Use the function from parent Widget
          child: Padding(
              padding: EdgeInsets.symmetric(vertical: 13),
              child: Text(
                text,
                style: TextStyle(fontWeight: FontWeight.bold),
              )),
          color: COLOR_BLUE,
          textColor: Colors.white,
          shape:
              RoundedRectangleBorder(borderRadius: BorderRadius.circular(25)),
        ),
      ),
    );
  }
}

然后在父 Widget 中，我想将 onPressed 方法传递给此按钮小部件:

...
myMethod () => {
   // do some stuff
}
...
Padding(
    padding: EdgeInsets.only(bottom: 10),
    child: Button("Log in", myMethod),
),
...

我如何告诉按钮小部件将 myMethod 用于 onPress？

Answer 1

使用 VoidCallback 类型，像这样。查看代码的行注释以获取更多信息:

class Button extends StatelessWidget {
  final String text;
  final VoidCallback callback; // Notice the variable type

  Button(this.text, this.callback);

  @override
  Widget build(BuildContext context) {
    return Container(
      height: 50,
      child: SizedBox(
        width: double.infinity,
        child: RaisedButton(
          onPressed: callback, // Simply put the function name here, DON'T use ()
          child: Padding(
              padding: EdgeInsets.symmetric(vertical: 13),
              child: Text(
                text,
                style: TextStyle(fontWeight: FontWeight.bold),
              )),
          color: COLOR_BLUE,
          textColor: Colors.white,
          shape:
              RoundedRectangleBorder(borderRadius: BorderRadius.circular(25)),
        ),
      ),
    );
  }
}