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我正在尝试创建一个功能来退出应用程序时双击返回按钮在CupertinoTabbar.

虽然我已经应用了各种功能，例如DoubleBackToCloseApp插件或WillPopScope，但每当我点击后退按钮时，都会出现退出消息。

因此，我想构建一个代码工作，如下所示：

  • 只需点击一次返回按钮，在页面之前返回
  • 在几秒钟内点击两次，退出应用程序。

我的标签栏如下：

class TabPage extends StatefulWidget {

  final FirebaseUser currentUser;

  TabPage(this.currentUser);

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

class _TabPageState extends State<TabPage> {
  int _selectedIndex = 0;

  static const snackBarDuration = Duration(seconds: 1);

  DateTime backbuttonpressedTime;


  final FirebaseMessaging _firebaseMessaging = FirebaseMessaging();

  final GlobalKey<NavigatorState> homeTabNavKey = GlobalKey<NavigatorState>();
  final GlobalKey<NavigatorState> groupTabNavKey = GlobalKey<NavigatorState>();
  final GlobalKey<NavigatorState> feedTabNavKey = GlobalKey<NavigatorState>();
  final GlobalKey<NavigatorState> userTabNavKey = GlobalKey<NavigatorState>();

  @override
  void initState() {
    _firebaseMessaging.onTokenRefresh.listen(sendTokenToServer);
    _firebaseMessaging.getToken();
  }

  @override
  Widget build(BuildContext context) {
    return WillPopScope(
      onWillPop: () async {
        return !await currentNavigatorKey().currentState.maybePop();
      },
      child: Scaffold(
        body: WillPopScope(
          onWillPop: _onWillPop,
          child: CupertinoTabScaffold(
            tabBar: CupertinoTabBar(
              activeColor: Theme
                  .of(context)
                  .colorScheme
                  .mainColor,
              inactiveColor: Theme
                  .of(context)
                  .colorScheme
                  .greyColor,
              items: [
                BottomNavigationBarItem(
                    icon: Icon(Icons.home)),
                BottomNavigationBarItem(
                    icon: Icon(Icons.group)),
                BottomNavigationBarItem(
                    icon: Icon(Icons.favorite_border)),
                BottomNavigationBarItem(
                    icon: Icon(Icons.account_circle)),
              ],
              onTap: (index) {
                // back home only if not switching tab
                if (_selectedIndex == index) {
                  switch (index) {
                    case 0:
                      homeTabNavKey.currentState.popUntil((r) => r.isFirst);
                      break;
                    case 1:
                      groupTabNavKey.currentState.popUntil((r) => r.isFirst);
                      break;
                    case 2:
                      feedTabNavKey.currentState.popUntil((r) => r.isFirst);
                      break;
                    case 3:
                      userTabNavKey.currentState.popUntil((r) => r.isFirst);
                      break;
                  }
                }
                _selectedIndex = index;
              },
            ),
            tabBuilder: (BuildContext context, int index) {
              switch (index) {
                case 0:
                  return CupertinoTabView(
                    navigatorKey: homeTabNavKey,
                    builder: (BuildContext context) => HomePage(),
                  );
                  break;
                case 1:
                  return CupertinoTabView(
                    navigatorKey: groupTabNavKey,
                    builder: (BuildContext context) => GroupPage(),
                  );
                  break;
                case 2:
                  return CupertinoTabView(
                    navigatorKey: feedTabNavKey,
                    builder: (BuildContext context) => FeedPage(widget.currentUser),
                  );
                  break;
                case 3:
                  return CupertinoTabView(
                    navigatorKey: userTabNavKey,
                    builder: (BuildContext context) =>
                        UserPage(widget.currentUser?.uid),
                  );
                  break;
              }
              return null;
            },
          ),
        ),
      ),
    );
  }

  void sendTokenToServer(String fcmToken) {
    print('Token: $fcmToken');

    Firestore.instance.collection('pushtokens')
        .document(widget.currentUser.uid)
        .setData({
      'pushToken': fcmToken
    });
  }

  GlobalKey<NavigatorState> currentNavigatorKey() {
    switch (_selectedIndex) {
      case 0:
        return homeTabNavKey;
        break;
      case 1:
        return groupTabNavKey;
        break;
      case 2:
        return feedTabNavKey;
        break;
      case 3:
        return userTabNavKey;
        break;
    }

    return null;
  }

//
  Future<bool> _onWillPop() async {
    DateTime currentTime = DateTime.now();
    //Statement 1 Or statement2
    bool backButton = backbuttonpressedTime == null ||
        currentTime.difference(backbuttonpressedTime) > Duration(seconds: 2);
    if (backButton) {
      backbuttonpressedTime = currentTime;
      Fluttertoast.showToast(
          msg: "Double Click to exit app",
          backgroundColor: Colors.black,
          textColor: Colors.white);
      return false;
    }
    return true;
  }
}

谢谢！

我终于解决了这个问题。我将发布更新的代码！

  int backbuttonpressedTime = 0;
  Future<bool> _onWillPop() async {
    var currentTime = DateTime.now().millisecondsSinceEpoch;

    if(!currentNavigatorKey().currentState.canPop()) {
      if (currentTime-backbuttonpressedTime < Duration(seconds: 2).inMilliseconds) {
        return SystemChannels.platform.invokeMethod('SystemNavigator.pop');
      }else{
        Fluttertoast.showToast(
            msg: "Double Click to exit app",
            backgroundColor: Colors.black,
            timeInSecForIos: 1,
            textColor: Colors.white);
        backbuttonpressedTime = currentTime;
        return false;
      }
    }else{
      return true;
    }
  }

我只修改_onWillPop()了一部分。谢谢！

4

1 回答 1

0

在简单的情况下，当您需要拦截 Android 后退按钮时，通常会将 WillPopScope 添加到您的小部件树中。但是，在开发与后退按钮交互的有状态小部件时，使用 BackButtonInterceptor 会更方便。看一看：

https://pub.dev/packages/back_button_interceptor

于 2020-03-08T21:18:47.727 回答