关于flutter:全局监听路由堆栈变化

老孟导读 ：很多时候咱们须要监听路由堆栈的变动，这样能够自定义路由堆栈、不便剖析异样日志等。

监听路由堆栈的变动应用 RouteObserver，首先在 MaterialApp 组件中增加 navigatorObservers：

void main() {runApp(MyApp());
}

RouteObserver<PageRoute> routeObserver = RouteObserver<PageRoute>();

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      ...
      navigatorObservers: [routeObserver],
      home: HomePage(),);
  }
}

监听页面设置如下：

class ARouteObserverDemo extends StatefulWidget {
  @override
  _RouteObserverDemoState createState() => _RouteObserverDemoState();
}

class _RouteObserverDemoState extends State<ARouteObserverDemo> with RouteAware {

  @override
  void didChangeDependencies() {super.didChangeDependencies();
    routeObserver.subscribe(this, ModalRoute.of(context));
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Container(
        alignment: Alignment.center,
        child: RaisedButton(child: Text('A RouteObserver'),
          onPressed: () {Navigator.of(context).pushNamed('/BRouteObserver');
          },
        ),
      ),
    );
  }

  @override
  void dispose() {super.dispose();
    routeObserver.unsubscribe(this);
  }

  @override
  void didPush() {final route = ModalRoute.of(context).settings.name;
    print('A-didPush route: $route');
  }

  @override
  void didPopNext() {final route = ModalRoute.of(context).settings.name;
    print('A-didPopNext route: $route');
  }

  @override
  void didPushNext() {final route = ModalRoute.of(context).settings.name;
    print('A-didPushNext route: $route');
  }

  @override
  void didPop() {final route = ModalRoute.of(context).settings.name;
    print('A-didPop route: $route');
  }

}

其中 didPush、didPushNext、didPopNext、didPop 为路由堆栈变动的回调。

从 A 页面跳转到 ARouteObserverDemo 页面，日志输入如下：

flutter: A-didPush route: /ARouteObserver

进入此页面只调用了 didPush。

从 ARouteObserverDemo 页面跳转到 BRouteObserverDemo 页面（同 ARouteObserverDemo 页面，设置了监听），日志输入如下：

flutter: A-didPushNext route: /ARouteObserver
flutter: B-didPush route: /BRouteObserver

先调用了 ARouteObserverDemo 页面的 didPushNext，而后调用了 BRouteObserverDemo 页面的 didPush。

从 BRouteObserverDemo 页面执行 pop 返回 ARouteObserverDemo 页面，日志输入如下：

flutter: A-didPopNext route: /ARouteObserver
flutter: B-didPop route: /BRouteObserver

先调用了 ARouteObserverDemo 页面的 didPopNext，而后调用了 BRouteObserverDemo 页面的 didPop。

下面的案例仅仅是页面级别的路由堆栈变动，如果想晓得整个应用程序路由堆栈变动如何解决？

一种办法是写一个监听路由堆栈的基类，所有页面继承此基类。此办法对源代码的侵入性十分高。

还有一种办法是自定义 RouteObserver，继承 RouteObserver 并重写其中的办法：

class MyRouteObserver<R extends Route<dynamic>> extends RouteObserver<R> {
  @override
  void didPush(Route route, Route previousRoute) {super.didPush(route, previousRoute);
    print('didPush route: $route,previousRoute:$previousRoute');
  }

  @override
  void didPop(Route route, Route previousRoute) {super.didPop(route, previousRoute);
    print('didPop route: $route,previousRoute:$previousRoute');
  }

  @override
  void didReplace({Route newRoute, Route oldRoute}) {super.didReplace(newRoute: newRoute, oldRoute: oldRoute);
    print('didReplace newRoute: $newRoute,oldRoute:$oldRoute');
  }

  @override
  void didRemove(Route route, Route previousRoute) {super.didRemove(route, previousRoute);
    print('didRemove route: $route,previousRoute:$previousRoute');
  }

  @override
  void didStartUserGesture(Route route, Route previousRoute) {super.didStartUserGesture(route, previousRoute);
    print('didStartUserGesture route: $route,previousRoute:$previousRoute');
  }

  @override
  void didStopUserGesture() {super.didStopUserGesture();
    print('didStopUserGesture');
  }
}

应用：

void main() {runApp(MyApp());
}

MyRouteObserver<PageRoute> myRouteObserver = MyRouteObserver<PageRoute>();

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      navigatorObservers: [myRouteObserver],
      initialRoute: '/A',
      home: APage(),);
  }
}

此时从 A 页面 跳转到 B 页面，日志输入如下：

flutter: didPush route: MaterialPageRoute<dynamic>(RouteSettings("/B", 来自 A), animation: AnimationController#6d429(▶ 0.000; for MaterialPageRoute<dynamic>(/B))),previousRoute:MaterialPageRoute<dynamic>(RouteSettings("/A", null), animation: AnimationController#e60f7(⏭ 1.000; paused; for MaterialPageRoute<dynamic>(/A)))

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