所有的问题都解决了。

将观察者从小部件树（materialappwidget）的根放置在导航器上。

如果您需要更多说明，请访问此链接：https : //api.flutter.dev/flutter/widgets/RouteObserver-
class.html

我已经在我的项目中实现了它，并且工作得很好@ Sp4Rx

// Register the RouteObserver as a navigation observer.
final RouteObserver<PageRoute> routeObserver = 
  RouteObserver<PageRoute>();
  void main() {
runApp(MaterialApp(
home: Container(),
navigatorObservers: [routeObserver],
 ));
   }

 class RouteAwareWidget extends StatefulWidget {
  State<RouteAwareWidget> createState() => RouteAwareWidgetState();
 }

 // Implement RouteAware in a widget's state and subscribe it to 
  the 
  RouteObserver.
  class RouteAwareWidgetState extends State<RouteAwareWidget> with 
 RouteAware {

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

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

@override
void didPush() {
  // Route was pushed onto navigator and is now topmost route.
}

 @override
void didPopNext() {
  // Covering route was popped off the navigator.
 }

@override
Widget build(BuildContext context) => Container();

 }