使用 NavController

如何解决使用 NavController

我正在尝试应用我所看到的关于带有 Fragment 和 MVVM“新组件”的导航抽屉活动的课程，在这个简单的应用程序中，我尝试使用三个 Fragment 在它们之间导航 navController.addOnDestinationChangedListener 并显示吐司消息，但似乎代码不起作用，我不知道原因

这是我的代码

public class MainActivity extends AppCompatActivity {

    private AppBarConfiguration mAppBarConfiguration;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Toolbar toolbar = findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);
        FloatingActionButton fab = findViewById(R.id.fab);

        FragmentManager fragmentManager = getSupportFragmentManager();
        FragmentTransaction fragmentTransaction = 
        fragmentManager.beginTransaction();

        fab.setonClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Snackbar.make(view,"Replace with your own action",Snackbar.LENGTH_LONG)
                        .setAction("Action",null).show();
            }
        });
        DrawerLayout drawer = findViewById(R.id.drawer_layout);
        NavigationView navigationView = findViewById(R.id.nav_view);
        // Passing each menu ID as a set of Ids because each
        // menu should be considered as top level destinations.
        mAppBarConfiguration = new AppBarConfiguration.Builder(
                R.id.nav_home,R.id.nav_gallery,R.id.nav_slideshow)
                .setDrawerLayout(drawer)
                .build();
        NavController navController = Navigation.findNavController(this,R.id.nav_host_fragment);
        NavigationUI.setupActionBarWithNavController(this,navController,mAppBarConfiguration);
        NavigationUI.setupWithNavController(navigationView,navController);

        navController.addOnDestinationChangedListener(new NavController.OnDestinationChangedListener() {
            @Override
            public void onDestinationChanged(@NonNull NavController controller,@NonNull NavDestination destination,@Nullable Bundle arguments) {

                int menuId = destination.getId();
                switch (menuId){
                    case R.id.nav_gallery:
                        fab.hide();
                        Toast.makeText(getApplicationContext(),"gallery",Toast.LENGTH_LONG).show();
                        fragmentTransaction.replace(R.id.homeFragment,new galleryFragment());
                        fragmentTransaction.addToBackStack(null);
                        fragmentTransaction.commit();

                        NavGraph navGraph = new NavGraph()

//                        controller.getGraph().clear();
//                        controller.navigate(R.id.nav_gallery);


                        break;
                    case R.id.nav_slideshow:
                        fab.hide();
                        Toast.makeText(getApplicationContext(),"Slideshow",Toast.LENGTH_LONG).show();
                        break;


                }

            }
        });

    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main,menu);
        return true;
    }

    @Override
    public boolean onSupportNavigateUp() {
        NavController navController = Navigation.findNavController(this,R.id.nav_host_fragment);
        return NavigationUI.navigateUp(navController,mAppBarConfiguration)
                || super.onSupportNavigateUp();
    }
}

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.drawerlayout.widget.DrawerLayout 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:id="@+id/drawer_layout"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:fitsSystemWindows="true"
    tools:openDrawer="start">

    <com.google.android.material.navigation.NavigationView
        android:id="@+id/nav_view"
        android:layout_width="wrap_content"
        android:layout_height="match_parent"
        android:layout_gravity="start"
        android:fitsSystemWindows="true"
        app:headerLayout="@layout/nav_header_main"
        app:menu="@menu/activity_main_drawer" />

    <include
        layout="@layout/app_bar_main"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />
</androidx.drawerlayout.widget.DrawerLayout>

content.main.xml

<?xml version="1.0" encoding="utf-8"?>
<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="match_parent"
    app:layout_behavior="@string/appbar_scrolling_view_behavior"
    tools:showIn="@layout/app_bar_main">

    <fragment
        android:id="@+id/nav_host_fragment"
        android:name="androidx.navigation.fragment.NavHostFragment"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        app:defaultNavHost="true"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:navGraph="@navigation/mobile_navigation" />
</androidx.constraintlayout.widget.ConstraintLayout>

mobile_navigation.xml

<?xml version="1.0" encoding="utf-8"?>
<navigation 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:id="@+id/mobile_navigation"
    app:startDestination="@+id/nav_home">

    <fragment
        android:id="@+id/nav_home"
        android:name="com.test.dummyappv3.ui.home.HomeFragment"
        android:label="@string/menu_home"
        tools:layout="@layout/fragment_home" />

    <fragment
        android:id="@+id/nav_gallery"
        android:name="com.test.dummyappv3.ui.gallery.galleryFragment"
        android:label="@string/menu_gallery"
        tools:layout="@layout/fragment_gallery" />

    <fragment
        android:id="@+id/nav_slideshow"
        android:name="com.test.dummyappv3.ui.slideshow.SlideshowFragment"
        android:label="@string/menu_slideshow"
        tools:layout="@layout/fragment_slideshow" />
</navigation>

在寻找解决方案时，我发现了这个 answer，并尝试像这样使用控制器

controller.getGraph().clear();
controller.navigate(R.id.nav_gallery);

而不是使用片段事务，但它也不起作用

解决方法

问题在这里

    <include
        layout="@layout/app_bar_main"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

将这个包含从这里移到 NavigationView 的顶部

<?xml version="1.0" encoding="utf-8"?>
<androidx.drawerlayout.widget.DrawerLayout 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:id="@+id/drawer_layout"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:fitsSystemWindows="true"
    tools:openDrawer="start">

    <include
        layout="@layout/app_bar_main"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

    <com.google.android.material.navigation.NavigationView
        android:id="@+id/nav_view"
        android:layout_width="wrap_content"
        android:layout_height="match_parent"
        android:layout_gravity="start"
        android:fitsSystemWindows="true"
        app:headerLayout="@layout/nav_header_main"
        app:menu="@menu/activity_main_drawer" />



</androidx.drawerlayout.widget.DrawerLayout>

然后一切都会好的

好的，你需要了解两件事。

NavigationController 与 FragmentManager 没有任何共同之处，只是它也可以交换 Fragment。
应用您的课程，您需要决定使用 FragmentManager 还是 NavigationController。

同时使用两者不仅会使您感到困惑，而且可能会使应用程序本身崩溃。

如何解决使用 NavController

解决方法

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