如何让BottomNavigation重选时回到嵌套导航起始目的地？

核心思路是利用Navigation组件的OnItemReselectedListener监听底部导航的重复点击事件，配合导航图中配置的Action，实现回到对应嵌套导航的起始页面。

1. 确认导航图的Action配置 #

你的navigation.xml中已经为navigation_nested3（notification嵌套导航图）配置了正确的返回Action，这个配置可以保留：

<action
    android:id="@+id/action_navigation_nested3_self"
    app:destination="@id/navigation_notifications"
    app:launchSingleTop="true"
    app:popUpTo="@id/navigation_notifications"
    app:popUpToInclusive="true"/>

• popUpTo + popUpToInclusive="true"：清除嵌套导航图内从起始页到当前页面的所有栈元素，确保回到纯净的起始页
• launchSingleTop="true"：避免重复创建起始页实例，提升性能

如果需要给home、dashboard也实现相同功能，可在对应嵌套图中添加同款Action：

<!-- 给navigation_nested1添加返回起始页的Action -->
<navigation
    android:id="@+id/navigation_nested1"
    app:startDestination="@id/navigation_home">
    <fragment
        android:id="@+id/navigation_home"
        android:name="com.example.myvagtest.ui.home.HomeFragment"
        android:label="@string/title_home"
        tools:layout="@layout/fragment_home" />
        
    <action
        android:id="@+id/action_navigation_nested1_self"
        app:destination="@id/navigation_home"
        app:launchSingleTop="true"
        app:popUpTo="@id/navigation_home"
        app:popUpToInclusive="true"/>
</navigation>

<!-- 给navigation_nested2添加返回起始页的Action -->
<navigation
    android:id="@+id/navigation_nested2"
    app:startDestination="@id/navigation_dashboard">
    <fragment
        android:id="@+id/navigation_dashboard"
        android:name="com.example.myvagtest.ui.dashboard.DashboardFragment"
        android:label="@string/title_dashboard"
        tools:layout="@layout/fragment_dashboard" />
        
    <action
        android:id="@+id/action_navigation_nested2_self"
        app:destination="@id/navigation_dashboard"
        app:launchSingleTop="true"
        app:popUpTo="@id/navigation_dashboard"
        app:popUpToInclusive="true"/>
</navigation>

2. 在MainActivity中设置重选监听 #

修改MainActivity，添加底部导航的重选监听逻辑，重复点击已选中的菜单项时触发回到起始页：

完整修改后的代码：

package com.example.myvagtest;

import android.os.Bundle;
import android.view.MenuItem;

import com.google.android.material.bottomnavigation.BottomNavigationView;
import com.google.android.material.navigation.NavigationBarView;

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

import com.example.myvagtest.databinding.ActivityMainBinding;

import java.util.HashSet;
import java.util.Set;

public class MainActivity extends AppCompatActivity {

    private ActivityMainBinding binding;
    private NavController navController;
    private BottomNavigationView navView;

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

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

        navView = findViewById(R.id.nav_view);

        AppBarConfiguration appBarConfiguration = new AppBarConfiguration.Builder(
                R.id.navigation_nested3,R.id.navigation_nested2,R.id.navigation_nested1).build();
        navController = Navigation.findNavController(this, R.id.nav_host_fragment_activity_main);
        NavigationUI.setupActionBarWithNavController(this, navController, appBarConfiguration);
        NavigationUI.setupWithNavController(navView, navController);
        
        // 初始化底部导航重选监听
        setupBottomNavigationReselection();
    }

    private void setupBottomNavigationReselection() {
        navView.setOnItemReselectedListener(new NavigationBarView.OnItemReselectedListener() {
            @Override
            public void onNavigationItemReselected(@NonNull MenuItem item) {
                int itemId = item.getItemId();
                // 根据菜单项ID匹配对应嵌套图的返回Action
                if (itemId == R.id.navigation_nested1) {
                    navController.navigate(R.id.action_navigation_nested1_self);
                } else if (itemId == R.id.navigation_nested2) {
                    navController.navigate(R.id.action_navigation_nested2_self);
                } else if (itemId == R.id.navigation_nested3) {
                    navController.navigate(R.id.action_navigation_nested3_self);
                }
            }
        });
    }
}

逻辑说明 #

• OnItemReselectedListener：仅在用户点击当前已选中的底部菜单项时触发，不会干扰正常的导航切换行为
• 导航Action的popUpTo配置：确保嵌套导航图内的页面栈被清空，彻底回到起始页，避免栈内堆积无效页面
• launchSingleTop="true"：如果起始页已经在栈顶，不会重复创建新实例，减少内存消耗

内容的提问来源于stack exchange，提问作者Saulius Lipkevičius