如何将 onPressed 值发送到另一个小部件 Flutter

Posted 2023-02-19

【中文标题】如何将 onPressed 值发送到另一个小部件 Flutter

【英文标题】：How to send onPressed value to another widget Flutter

【发布时间】：2021-12-12 07:42:41

【问题描述】：

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,
    );
  

【问题讨论】：

How to access Stateful widget variable inside State class outside the build method?的可能重复

CancelAppBar(onPressed: yourOnPressedFunction)

【参考方案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,
    );
  

【讨论】：

还有，调用CancelAppBar()时应该写什么参数