导航到片段后无法返回菜单（带 gif）答案

【问题标题】：Unable to go back through menu after navigation to fragment (with gif)导航到片段后无法返回菜单（带 gif）
【发布时间】：2022-08-13 21:35:03
【问题描述】：

Gif showing the problem

我正在使用最新 Android Studio（2021.2.1 补丁 2）中的“导航抽屉活动”模板作为开始。

通过单击 imageViews，我能够以编程方式在片段之间导航。

但是在这些成功的导航之后，单击菜单中的“主页”项不起作用。 (Gif)

https://developer.android.com/guide/navigation/navigation-navigate https://developer.android.com/guide/navigation/navigation-programmatic

HomeFragment.java：（已编辑）

final ImageView imageView = binding.imageView2;
imageView.setOnClickListener(new View.OnClickListener() {
    public void onClick(View v) {
        Fragment navHostFragment = getActivity().getSupportFragmentManager().findFragmentById(R.id.nav_host_fragment_content_main);
        NavController navController = NavHostFragment.findNavController(navHostFragment);
        navController.navigate(R.id.nav_slideshow);
    }
});

SlideshowFragment.java：（已编辑）

final ImageView imageView = binding.imageView3;
imageView.setOnClickListener(new View.OnClickListener() {
    public void onClick(View v) {
        Fragment navHostFragment = getActivity().getSupportFragmentManager().findFragmentById(R.id.nav_host_fragment_content_main);
        NavController navController = NavHostFragment.findNavController(navHostFragment);
        navController.navigate(R.id.nav_home);
    }
});

MainActivity.java：（未编辑）

package com.example.try3;

import android.os.Bundle;
import android.view.View;
import android.view.Menu;

import com.google.android.material.snackbar.Snackbar;
import com.google.android.material.navigation.NavigationView;

import androidx.navigation.NavController;
import androidx.navigation.Navigation;
import androidx.navigation.ui.AppBarConfiguration;
import androidx.navigation.ui.NavigationUI;
import androidx.drawerlayout.widget.DrawerLayout;
import androidx.appcompat.app.AppCompatActivity;

import com.example.try3.databinding.ActivityMainBinding;

public class MainActivity extends AppCompatActivity {

    private AppBarConfiguration mAppBarConfiguration;
    private ActivityMainBinding binding;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        binding = ActivityMainBinding.inflate(getLayoutInflater());
        setContentView(binding.getRoot());

        setSupportActionBar(binding.appBarMain.toolbar);
        binding.appBarMain.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 = binding.drawerLayout;
        NavigationView navigationView = binding.navView;
        // 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)
                .setOpenableLayout(drawer)
                .build();
        NavController navController = Navigation.findNavController(this, R.id.nav_host_fragment_content_main);
        NavigationUI.setupActionBarWithNavController(this, navController, mAppBarConfiguration);
        NavigationUI.setupWithNavController(navigationView, navController);
    }

    @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_content_main);
        return NavigationUI.navigateUp(navController, mAppBarConfiguration)
                || super.onSupportNavigateUp();
    }
}

fragment_home.xml：（未编辑）

<?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\"
    tools:context=\".ui.home.HomeFragment\">
    <ImageView
        android:id=\"@+id/imageView2\"
        android:layout_width=\"wrap_content\"
        android:layout_height=\"wrap_content\"
        android:src=\"@drawable/ic_launcher_background\"
        app:layout_constraintStart_toStartOf=\"parent\"
        app:layout_constraintTop_toTopOf=\"parent\" />
</androidx.constraintlayout.widget.ConstraintLayout>

fragment_slideshow.xml：（未编辑）

<?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\"
    tools:context=\".ui.slideshow.SlideshowFragment\">
    <ImageView
        android:id=\"@+id/imageView3\"
        android:layout_width=\"wrap_content\"
        android:layout_height=\"wrap_content\"
        android:src=\"@drawable/ic_launcher_background\"
        app:layout_constraintBottom_toBottomOf=\"parent\"
        app:layout_constraintEnd_toEndOf=\"parent\" />
</androidx.constraintlayout.widget.ConstraintLayout>

content_main.xml：（未编辑）

<?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_content_main\"
        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>

activity_main.xml：（未编辑）

<?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
        android:id=\"@+id/app_bar_main\"
        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>

activity_main_drawer.xml：（未编辑）

<?xml version=\"1.0\" encoding=\"utf-8\"?>
<menu xmlns:android=\"http://schemas.android.com/apk/res/android\"
    xmlns:tools=\"http://schemas.android.com/tools\"
    tools:showIn=\"navigation_view\">
    <group android:checkableBehavior=\"single\">
        <item
            android:id=\"@+id/nav_home\"
            android:icon=\"@drawable/ic_menu_camera\"
            android:title=\"@string/menu_home\" />
        <item
            android:id=\"@+id/nav_gallery\"
            android:icon=\"@drawable/ic_menu_gallery\"
            android:title=\"@string/menu_gallery\" />
        <item
            android:id=\"@+id/nav_slideshow\"
            android:icon=\"@drawable/ic_menu_slideshow\"
            android:title=\"@string/menu_slideshow\" />
    </group>
</menu>

mobile_navigation.xml：（未编辑）

<?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.example.try3.ui.home.HomeFragment\"
        android:label=\"@string/menu_home\"
        tools:layout=\"@layout/fragment_home\" />
    <fragment
        android:id=\"@+id/nav_gallery\"
        android:name=\"com.example.try3.ui.gallery.GalleryFragment\"
        android:label=\"@string/menu_gallery\"
        tools:layout=\"@layout/fragment_gallery\" />
    <fragment
        android:id=\"@+id/nav_slideshow\"
        android:name=\"com.example.try3.ui.slideshow.SlideshowFragment\"
        android:label=\"@string/menu_slideshow\"
        tools:layout=\"@layout/fragment_slideshow\" />
</navigation>

先感谢您。

标签： java android android-studio android-layout

【解决方案1】：

这是由于与元素关联的多个回栈。我们需要使用 NavigationUI.onNavDestinationSelected() 将目的地与菜单项联系起来。请覆盖主要活动中的 onOptionsItemSelected 函数。

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    NavController navController = Navigation.findNavController(this,
        R.id.nav_host_fragment_content_main);

    // By calling onNavDestinationSelected(), you always get the right behavior
    return NavigationUI.onNavDestinationSelected(item, navController)
            || super.onOptionsItemSelected(item);
}

【讨论】：