如何将 onPressed 值发送到另一个小部件 Flutter

Question

我想将数据从小部件发送到另一个小部件，在我的示例中，我想将 onPressed 值作为变量发送。

appBar: CancelAppBar(onPressed: ),

在 onPressed 之后（在上面的代码中）我应该写什么来发送值： Navigator.of(context).push(MaterialPageRoute(builder: (context) => UnderBuild()));

到单独的 dart 文件中的小部件？

下面是另一个文件：

class CancelAppBar extends StatefulWidget implements PreferredSizeWidget {
  CancelAppBar({Key? key, required this.onPressed}) : super(key: key);

  final ValueGetter<String> onPressed;
  static final _appBar = AppBar();
  @override
  Size get preferredSize => _appBar.preferredSize;

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

class _CancelAppBarState extends State<CancelAppBar> {
  get onPressed => null;

  @override
  Widget build(BuildContext context) {
    return AppBar(
      titleSpacing: 0.0,
      title: Row(
        mainAxisAlignment: MainAxisAlignment.start,
        children: <Widget>[
          Padding(padding: EdgeInsets.only(left: 8.w)),
          IconButton(
            onPressed: ,
            icon: Icon(Icons.close),
          )
        ],
      ),
      backgroundColor: AppColors.dark,
    );
  }
}

Answer 1

您可以使用widget getter 访问State 类中的任何StatefulWidget 变量，例如：

另外，你可以注意到：

• 您的onPressed 变量具有ValueGetter<String> 类型which is only a typedef to String Function()
• IconButton 小部件的onPressed 具有void Function() 类型

然后你可以像这样使用你的变量：

class CancelAppBar extends StatefulWidget implements PreferredSizeWidget {
  CancelAppBar({Key? key, required this.onPressed}) : super(key: key);

  final ValueGetter<String> onPressed;
  static final _appBar = AppBar();
  @override
  Size get preferredSize => _appBar.preferredSize;

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

class _CancelAppBarState extends State<CancelAppBar> {
  @override
  Widget build(BuildContext context) {
    return AppBar(
      titleSpacing: 0.0,
      title: Row(
        mainAxisAlignment: MainAxisAlignment.start,
        children: <Widget>[
          Padding(padding: EdgeInsets.only(left: 8.w)),
          IconButton(
            onPressed: () {
              /// Access your variable by [widget.onPressed]
              widget.onPressed(); /// Call it inside this function because your variable doesn't match directly the [onPressed] of [IconButton] widget
            },
            icon: Icon(Icons.close),
          )
        ],
      ),
      backgroundColor: AppColors.dark,
    );
  }
}