有没有办法配置 willPopScope 以在 flutter 中捕获自定义弹出导航？

Question

有没有办法配置 willPopScope 来捕获自定义弹出导航，如下所示？我有一个自定义 Raisingbutton 小部件，带有 onPressed 来导航回上一页。

但 willPopScope 不会像 AppBar 后退按钮那样捕获导航。我不确定这是否可能。请指教。谢谢！

WillPopScope(
 child: Scaffold(
  body: Container(
   child: Center(
    child: RaisedButton(
     onPressed:(){
      return Navigator.pop(context);
     },
     child: Text("Go Back),
    ),
   ),
  ),
 ),
 onWillPop: () async {
  // code to show a modal
 }
);

Answer 1

这是实现您的目标的完整示例。WillPopScope需要maybePop调用才能执行您的逻辑：

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);

  final String title;

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

class _MyHomePageState extends State<MyHomePage> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Center(
        child: RaisedButton(
          child: Text('Jump To Next Screen'),
          onPressed: () => Navigator.of(context)
              .push(MaterialPageRoute(builder: (_) => ModalScreen())),
        ),
      ), // This trailing comma makes auto-formatting nicer for build methods.
    );
  }
}

class ModalScreen extends StatefulWidget {
  @override
  _ModalScreenState createState() => _ModalScreenState();
}

class _ModalScreenState extends State<ModalScreen> {
  @override
  Widget build(BuildContext context) {
    return WillPopScope(
      child: Scaffold(
        appBar: AppBar(
          leading: InkResponse(
            child: Icon(Icons.arrow_back),
            onTap: () => Navigator.of(context).maybePop(),
          ),
        ),
        backgroundColor: Colors.blue,
        body: Center(
          child: RaisedButton(
            child: Text('Let\'s go back'),
            onPressed: () {
              Navigator.of(context).maybePop();
            },
          ),
        ),
      ),
      onWillPop: () => _willPop(context),
    );
  }

  Future<bool> _willPop(BuildContext context) {
    final completer = Completer<bool>();
    showModalBottomSheet(
        context: context,
        builder: (buildContext) {
          return SizedBox(
            height: 200,
            child: Column(
              children: [
                Padding(
                  padding: const EdgeInsets.symmetric(vertical: 20),
                  child: Text('Are you sure?'),
                ),
                MaterialButton(
                    child: Text('YES'),
                    onPressed: () {
                      completer.complete(true);
                      Navigator.of(context).pop();
                    }),
                MaterialButton(
                    child: Text('NO'),
                    onPressed: () {
                      completer.complete(true);
                    }),
              ],
            ),
          );
        });

    return completer.future;
  }
}

返回true模态框后，您还需要弹出屏幕，因为模态框有自己的上下文需要弹出。

最终结果如下：