如何让Scaffold的MoreActionsButton获取Body组件的当前状态信息？

下面提供两种实用方案，无需将FAB移入body组件即可实现需求：

方法一：通过GlobalKey直接访问Body组件状态 #

如果你的body是StatefulWidget，可以用GlobalKey直接获取它的内部状态和数据：

1. 给Body组件定义专属GlobalKey并暴露数据获取方法

class MyBodyWidget extends StatefulWidget {
  // 定义全局可访问的GlobalKey
  static final GlobalKey<MyBodyWidgetState> globalKey = GlobalKey<MyBodyWidgetState>();

  const MyBodyWidget({super.key});

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

class MyBodyWidgetState extends State<MyBodyWidget> {
  // 示例：body内需要获取的当前信息
  String currentContent = "初始内容";

  // 暴露获取信息的方法
  String getCurrentContent() {
    return currentContent;
  }

  @override
  Widget build(BuildContext context) {
    return Center(child: Text(currentContent));
  }
}

2. 修改MyScaffold，接收并传递Body的GlobalKey

class MyScaffold extends StatelessWidget {
  final MyFruit apple;
  final Widget body;
  final GlobalKey bodyKey; // 添加Body的key参数

  const MyScaffold({
    required this.apple,
    required this.body,
    required this.bodyKey,
    super.key,
  });

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: ...,
      body: body,
      floatingActionButton: MoreActionsButton(apple, bodyKey: bodyKey), // 传递key给按钮
      bottomNavigationBar: ...,
      key: key,
    );
  }
}

3. 在MoreActionsButton中用Key获取Body信息

class MoreActionsButton extends StatelessWidget {
  final MyFruit apple;
  final GlobalKey bodyKey;

  const MoreActionsButton(this.apple, {required this.bodyKey, super.key});

  @override
  Widget build(BuildContext context) {
    return FloatingActionButton(
      onPressed: () {
        showModalBottomSheet(
          context: context,
          builder: (context) {
            return Column(
              mainAxisSize: MainAxisSize.min,
              children: [
                ListTile(
                  title: const Text("获取Body当前信息"),
                  onTap: () {
                    // 通过Key获取Body状态并提取信息
                    if (bodyKey.currentState is MyBodyWidgetState) {
                      final content = (bodyKey.currentState as MyBodyWidgetState).getCurrentContent();
                      // 这里处理获取到的信息，比如弹窗提示、打印等
                      print(content);
                      Navigator.pop(context);
                    }
                  },
                ),
              ],
            );
          },
        );
      },
      child: const Icon(Icons.more_vert),
    );
  }
}

4. 使用时传入Body的GlobalKey

MyScaffold(
  apple: MyFruit(),
  body: MyBodyWidget(key: MyBodyWidget.globalKey),
  bodyKey: MyBodyWidget.globalKey,
)

方法二：通过回调函数传递信息 #

如果不想用GlobalKey，可以通过回调函数让Body主动提供信息：

1. 修改MyScaffold，添加获取信息的回调参数

class MyScaffold extends StatelessWidget {
  final MyFruit apple;
  final Widget body;
  final String Function() getBodyInfo; // 定义获取信息的回调

  const MyScaffold({
    required this.apple,
    required this.body,
    required this.getBodyInfo,
    super.key,
  });

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: ...,
      body: body,
      floatingActionButton: MoreActionsButton(apple, getBodyInfo: getBodyInfo), // 传递回调
      bottomNavigationBar: ...,
      key: key,
    );
  }
}

2. 修改MoreActionsButton使用回调获取信息

class MoreActionsButton extends StatelessWidget {
  final MyFruit apple;
  final String Function() getBodyInfo;

  const MoreActionsButton(this.apple, {required this.getBodyInfo, super.key});

  @override
  Widget build(BuildContext context) {
    return FloatingActionButton(
      onPressed: () {
        showModalBottomSheet(
          context: context,
          builder: (context) {
            return Column(
              mainAxisSize: MainAxisSize.min,
              children: [
                ListTile(
                  title: const Text("获取Body当前信息"),
                  onTap: () {
                    final info = getBodyInfo();
                    // 处理获取到的信息
                    print(info);
                    Navigator.pop(context);
                  },
                ),
              ],
            );
          },
        );
      },
      child: const Icon(Icons.more_vert),
    );
  }
}

3. 使用时传入回调函数

final bodyKey = GlobalKey<MyBodyWidgetState>();

MyScaffold(
  apple: MyFruit(),
  body: MyBodyWidget(key: bodyKey),
  getBodyInfo: () => bodyKey.currentState!.getCurrentContent(),
)

内容的提问来源于stack exchange，提问作者Vasudev