BottomNavigationView 中的多 NavHost

如何解决BottomNavigationView 中的多 NavHost

我想用 BottomNavigationView 创建多个 NavHostFragment 来保存每个选项卡的状态。但是当我在选项卡之间切换时，navControllers 将返回到每个选项卡的 StartDestination。我遵循 https://github.com/moallemi/MultiNavHost 中的示例，这是我的代码： 1.主要活动：

public class MainActivity extends AppCompatActivity {
    
    private BottomNavigationView bottomNavView;
    private NavController currentController;
    private AppBarConfiguration appBarConfiguration;
    private TabManager tabManager;
    private FrameLayout homeContainer,searchContainer,favoriteContainer,recentContainer;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        initControl();
    }

    @SuppressLint("ResourceType")
    private void initControl() {
        homeContainer= findViewById(R.id.homeContainer);
        searchContainer= findViewById(R.id.searhContainer);
        favoriteContainer= findViewById(R.id.favoriteContainer);
        recentContainer= findViewById(R.id.recentContainer);
        bottomNavView = findViewById(R.id.nav_view);
        tabManager= new TabManager(this);
        currentController= tabManager.getHomeController();
        appBarConfiguration= new AppBarConfiguration.Builder(R.id.nav_home,R.id.nav_search,R.id.nav_favorite,R.id.nav_recent).build();
        NavigationUI.setupWithNavController(bottomNavView,currentController);
        bottomNavView.setonNavigationItemSelectedListener(item -> {
            switchTab(item.getItemId());
            return true;
        });
        bottomNavView.setSelectedItemId(R.id.nav_home);
    }

    @SuppressLint("RestrictedApi")
    private void switchTab(int itemId) {
        switch (itemId){
            case R.id.nav_home:
                currentController= tabManager.getHomeController();
                setTabContainerInvisible();
                homeContainer.setVisibility(View.VISIBLE);
                NavigationUI.setupActionBarWithNavController(this,currentController,appBarConfiguration);
                break;
            case R.id.nav_search:
                currentController= tabManager.getSearchController();
                setTabContainerInvisible();
                searchContainer.setVisibility(View.VISIBLE);
                NavigationUI.setupActionBarWithNavController(this,appBarConfiguration);
                break;
            case R.id.nav_favorite:
                currentController= tabManager.getFavoriteController();
                setTabContainerInvisible();
                favoriteContainer.setVisibility(View.VISIBLE);
                NavigationUI.setupActionBarWithNavController(this,appBarConfiguration);
                break;
            case R.id.nav_recent:
                currentController= tabManager.getRecentController();
                setTabContainerInvisible();
                recentContainer.setVisibility(View.VISIBLE);
                NavigationUI.setupActionBarWithNavController(this,appBarConfiguration);
                break;
        }
    }

    private void setTabContainerInvisible(){
        homeContainer.setVisibility(View.INVISIBLE);
        searchContainer.setVisibility(View.INVISIBLE);
        favoriteContainer.setVisibility(View.INVISIBLE);
        recentContainer.setVisibility(View.INVISIBLE);
    }

2.TabManager

public class TabManager {

    private MainActivity mainActivity;

    public TabManager(MainActivity mainActivity) {
        this.mainActivity = mainActivity;
    }

    @SuppressLint("ResourceType")
    public NavController getHomeController(){
        NavController homeController= Navigation.findNavController(mainActivity,R.id.home_nav_host_fragment);
        NavGraph graph= homeController.getNavInflater().inflate(R.navigation.nav_graph);
        graph.setStartDestination(R.id.nav_home);
        homeController.setGraph(graph);
        return homeController;
    }
... setup another tab

3.NavGraph xml

<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="0dp"
    app:layout_behavior="@string/appbar_scrolling_view_behavior"
    tools:showIn="@layout/app_bar_main">

    <FrameLayout
        android:id="@+id/homeContainer"
        android:visibility="visible"
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <fragment
            android:id="@+id/home_nav_host_fragment"
            android:name="androidx.navigation.fragment.NavHostFragment"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            app:defaultNavHost="false"
            app:layout_constraintLeft_toLeftOf="parent"
            app:layout_constraintRight_toRightOf="parent"
            app:layout_constraintTop_toTopOf="parent" />

    </FrameLayout>
   ... <FrameLayout>... </FrameLayout>