flutter - 单击后退按钮时设置方向

Question

我在第一个屏幕上设置了2个屏幕，我设置了横向，在第二个屏幕上，当我弹出第二个屏幕时又应用了纵向，回到第一个屏幕仍然设置为纵向，我该如何解决此问题，我应该将这些行放在哪里代码，这样我回到主屏幕时就可以重新定向。

import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
void main() {
  runApp(
      MaterialApp(
    debugShowCheckedModeBanner: false,
    home: won(),
  ));
}
class won extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    SystemChrome.setPreferredOrientations(
        [DeviceOrientation.landscapeLeft, DeviceOrientation.landscapeRight]);
    return Scaffold(
      body: Center(
        child: RaisedButton(
          onPressed: () {
            Navigator.push(
              context,
              MaterialPageRoute(builder: (context) => won1()),
            );
          },
          child: Text('Forward'),
        ),
      ),
    );
  }
}
class won1 extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    SystemChrome.setPreferredOrientations(
        [DeviceOrientation.portraitUp, DeviceOrientation.portraitDown]);
    return Scaffold(
      body: Center(
        child: RaisedButton(
          onPressed: () {
            Navigator.pop(context);
          },
          child: Text('Back'),
        ),
      ),
    );
  }
}

Answer 1

我通过使用RouteObserver(https://api.flutter.dev/flutter/widgets/RouteObserver-class.html)成功处理了它
导航时使用此选项传递屏幕名称:

Navigator.of(context)
        .push(MaterialPageRoute(
            builder: (context) => w,
            settings: RouteSettings(name: w.runtimeType.toString())))
        .then((value) {
      if (value == null) {
        widget.getHomepageData();
      }
    });

然后通过向MaterialApp添加观察者来检测和处理屏幕变化(向前或向后导航):

return MaterialApp(
                    builder: (BuildContext context, Widget child) {
                      return MediaQuery(
                        data: MediaQuery.of(context).copyWith(
                            textScaleFactor: 1.0),
                        child: child,
                      );
                    },
                    home: GeneralStatelessWidget((ctx) => getHome(ctx)),
                    navigatorObservers: [
                      CustomRouteObserver()
            ],
                    onGenerateTitle: generateAppTitle);

这是自定义观察者:

import 'package:flutter/material.dart';
import 'package:tangerine/utils/flutter_device_type.dart';
import 'package:tangerine/utils/screen_functions.dart';

class CustomRouteObserver extends RouteObserver<PageRoute<dynamic>> {
  void _sendScreenView(PageRoute<dynamic> route) {
    var screenName = route.settings.name;
    final landscapeOnlyOnTablet = [
      "LandingPage",
      "/",
      "ProductScreen",
      "SearchScreen"
    ];
    if (landscapeOnlyOnTablet.contains(screenName)) {
      if (Device.get().isTablet) {
        allowLandscape();
      } else {
        denyLandscape();
      }
    } else {
      allowLandscape();
    }
  }

  @override
  void didPush(Route<dynamic> route, Route<dynamic> previousRoute) {
    super.didPush(route, previousRoute);
    if (route is PageRoute) {
      _sendScreenView(route);
    }
  }

  @override
  void didReplace({Route<dynamic> newRoute, Route<dynamic> oldRoute}) {
    super.didReplace(newRoute: newRoute, oldRoute: oldRoute);
    if (newRoute is PageRoute) {
      _sendScreenView(newRoute);
    }
  }

  @override
  void didPop(Route<dynamic> route, Route<dynamic> previousRoute) {
    super.didPop(route, previousRoute);
    if (previousRoute is PageRoute && route is PageRoute) {
      _sendScreenView(previousRoute);
    }
  }
}

void allowLandscape() {
  SystemChrome.setPreferredOrientations([
    DeviceOrientation.landscapeRight,
    DeviceOrientation.landscapeLeft,
    DeviceOrientation.portraitUp,
    DeviceOrientation.portraitDown,
  ]);
}

void denyLandscape() {
  SystemChrome.setPreferredOrientations([
    DeviceOrientation.portraitUp,
    DeviceOrientation.portraitDown,
  ]);
}