flutter - 如何在 Flutter 中进行嵌套导航

Question

有人对 Flutter 中的嵌套导航有什么建议吗？

我想要的是即使在重定向到新屏幕时也能保持持久的 BottomNavigationBar。与 YouTube 类似，即使您更深入地浏览菜单，底部栏也始终存在。

我无法从文档中弄清楚。

到目前为止，我能够找到的唯一深入了解我的要求的教程是https://medium.com/coding-with-flutter/flutter-case-study-multiple-navigators-with-bottomnavigationbar-90eb6caa6dbf （源代码）。然而，它超级混乱。

现在我正在使用

Navigator.push(context,
                MaterialPageRoute(builder: (BuildContext context) {
              return Container()

然而，它只是将新的小部件推到整个堆栈上，与 BottomNavigationBar 相辅相成。

任何提示将非常感谢！

Answer 1

这是一个简单的示例，它甚至支持使用标签栏弹出到第一个屏幕。

import 'package:flutter/material.dart';

import '../library/screen.dart';
import '../playlists/screen.dart';
import '../search/screen.dart';
import '../settings/screen.dart';

class TabsScreen extends StatefulWidget {
  @override
  _TabsScreenState createState() => _TabsScreenState();
}

class _TabsScreenState extends State<TabsScreen> {
  int _currentIndex = 0;

  final _libraryScreen = GlobalKey<NavigatorState>();
  final _playlistScreen = GlobalKey<NavigatorState>();
  final _searchScreen = GlobalKey<NavigatorState>();
  final _settingsScreen = GlobalKey<NavigatorState>();

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: IndexedStack(
        index: _currentIndex,
        children: <Widget>[
          Navigator(
            key: _libraryScreen,
            onGenerateRoute: (route) => MaterialPageRoute(
              settings: route,
              builder: (context) => LibraryScreen(),
            ),
          ),
          Navigator(
            key: _playlistScreen,
            onGenerateRoute: (route) => MaterialPageRoute(
              settings: route,
              builder: (context) => PlaylistsScreen(),
            ),
          ),
          Navigator(
            key: _searchScreen,
            onGenerateRoute: (route) => MaterialPageRoute(
              settings: route,
              builder: (context) => SearchScreen(),
            ),
          ),
          Navigator(
            key: _settingsScreen,
            onGenerateRoute: (route) => MaterialPageRoute(
              settings: route,
              builder: (context) => SettingsScreen(),
            ),
          ),
        ],
      ),
      bottomNavigationBar: BottomNavigationBar(
        type: BottomNavigationBarType.fixed,
        currentIndex: _currentIndex,
        onTap: (val) => _onTap(val, context),
        backgroundColor: Theme.of(context).scaffoldBackgroundColor,
        items: [
          BottomNavigationBarItem(
            icon: Icon(Icons.library_books),
            title: Text('Library'),
          ),
          BottomNavigationBarItem(
            icon: Icon(Icons.list),
            title: Text('Playlists'),
          ),
          BottomNavigationBarItem(
            icon: Icon(Icons.search),
            title: Text('Search'),
          ),
          BottomNavigationBarItem(
            icon: Icon(Icons.settings),
            title: Text('Settings'),
          ),
        ],
      ),
    );
  }

  void _onTap(int val, BuildContext context) {
    if (_currentIndex == val) {
      switch (val) {
        case 0:
          _libraryScreen.currentState.popUntil((route) => route.isFirst);
          break;
        case 1:
          _playlistScreen.currentState.popUntil((route) => route.isFirst);
          break;
        case 2:
          _searchScreen.currentState.popUntil((route) => route.isFirst);
          break;
        case 3:
          _settingsScreen.currentState.popUntil((route) => route.isFirst);
          break;
        default:
      }
    } else {
      if (mounted) {
        setState(() {
          _currentIndex = val;
        });
      }
    }
  }
}

Answer 2

以下是作为启动器的持久性 BottomNavigationBar 的示例代码：

import 'package:flutter/material.dart';

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: MainPage(),
    );
  }
}

class MainPage extends StatelessWidget {
  final navigatorKey = GlobalKey<NavigatorState>();

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Column(
        children: <Widget>[
          Expanded(
            child: Navigator(
              key: navigatorKey,
              onGenerateRoute: (route) => MaterialPageRoute(
                    settings: route,
                    builder: (context) => PageOne(),
                  ),
            ),
          ),
          BottomNavigationBar(navigatorKey)
        ],
      ),
    );
  }
}

class BottomNavigationBar extends StatelessWidget {
  final GlobalKey<NavigatorState> navigatorKey;

  BottomNavigationBar(this.navigatorKey) : assert(navigatorKey != null);

  Future<void> push(Route route) {
    return navigatorKey.currentState.push(route);
  }

  @override
  Widget build(BuildContext context) {
    return Container(
      color: Colors.blue,
      child: ButtonBar(
        alignment: MainAxisAlignment.spaceEvenly,
        children: <Widget>[
          RaisedButton(
            child: Text("PageOne"),
            onPressed: () {
              push(MaterialPageRoute(builder: (context) => PageOne()));
            },
          ),
          RaisedButton(
            child: Text("PageTwo"),
            onPressed: () {
              push(MaterialPageRoute(builder: (context) => PageTwo()));
            },
          )
        ],
      ),
    );
  }
}

class PageOne extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Container(
      child: Column(
        mainAxisAlignment: MainAxisAlignment.center,
        children: <Widget>[
          Text("Page One"),
          RaisedButton(
            onPressed: (){
              Navigator.of(context).pop();
            },
            child: Text("Pop"),
          ),
        ],
      ),
    );
  }
}

class PageTwo extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Container(
      child: Column(
        mainAxisAlignment: MainAxisAlignment.center,
        children: <Widget>[
          Text("Page Two"),
          RaisedButton(
            onPressed: (){
              Navigator.of(context).pop();
            },
            child: Text("Pop"),
          ),
        ],
      ),
    );
  }
}

这是屏幕记录的方式