Flutter onPressed Function

Question

onPressed出错 尝试传递onPressed函数但是出现了错误。

错误 - 参数类型'Function'不能被赋值给参数类型'void Function()?'.

class CircleButton extends StatelessWidget {
  CircleButton({required this.icon, required this.onPressed});
  final IconData icon;
  final Function onPressed;                 [![Error][1]][1]//Here
  @override
  Widget build(BuildContext context) {
    return ElevatedButton(
      child: Icon(icon),
      onPressed: onPressed,
      style: ElevatedButton.styleFrom(
        elevation: 6.0,
        primary: Color(0xFF4C4F5E),
        shape: CircleBorder(),
        padding: EdgeInsets.all(15),
      ),);
  }}

- Yash kolte

---

这个回答解决了你的问题吗？ [在使用空安全后，参数类型'Function'无法分配给参数类型'void Function()'] (https://dev59.com/O1IG5IYBdhLWcg3wiQ55) - Yeasin Sheikh

Answer 1

Function类型实际上是一个动态的Function类型。

ElevatedButton期望一个void Function来作为它的onPressed方法，实际上这个类型有一个别名typedef：VoidCallback

因此，请将您的Function onPressed替换为VoidCallback onPressed。

- Miguel Ruivo

Answer 2

将函数改为VoidCallback

class CircleButton extends StatelessWidget {
  CircleButton({required this.icon, required this.onPressed});
  final IconData icon;
  final VoidCallback onPressed;   //Change Function to VoidCallback
  @override
  Widget build(BuildContext context) {
    return ElevatedButton(
      onPressed: onPressed,
      child: Icon(icon),
      style: ElevatedButton.styleFrom(
        elevation: 6.0,
        primary: Color(0xFF4C4F5E),
        shape: CircleBorder(),
        padding: EdgeInsets.all(15),
      ),
    );
  }
}

- Yash kolte