自定义BottomNavigationView行为：切换标签时弹出搜索Fragment

我用BottomNavigationView做了三个标签页，第二个标签（B页，对应navigation_dashboard）是起始页。在B页执行搜索后，会打开Fragment D（navigation_laws_filtered），此时B页的导航栈变成 B -> D。按返回键能回到B页，但如果切换到A（navigation_home）或C（navigation_notifications）标签后再切回B，D页还会留在栈里显示。

Navigation组件的XML里支持popUpInclusive属性，但BottomNavigationView默认的导航不需要在XML里定义动作，我找不到重写这个行为的方法。试过监听OnItemViewSelectedListener但不知道后续怎么操作；用fragmentManager.replace()不够优雅；navigateUp()感觉合适但没正确用上，还怕不符合Navigation规范。想知道怎么实现「切换到其他标签时自动把搜索Fragment D从栈里弹出」的效果？

对应的导航XML代码：

<?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/navigation_dashboard">

    <fragment
        android:id="@+id/navigation_home"
        android:name="ru.home.government.screens.deputies.DeputiesFragment"
        android:label="@string/title_deputies"
        tools:layout="@layout/fragment_deputies">
        <argument
            android:name="EXTRA_NO_BOTTOM_VIEW"
            app:argType="boolean"
            android:defaultValue="false" />

        <action
            android:id="@+id/action_navigation_home_to_navigation_dashboard"
            app:destination="@id/navigation_dashboard"
            app:popUpTo="@+id/navigation_home"
            app:popUpToInclusive="true" />

    </fragment>

    <fragment
        android:id="@+id/navigation_dashboard"
        android:name="ru.home.government.screens.laws.main.LawsMainFragment"
        android:label="@string/title_laws"
        tools:layout="@layout/fragment_laws" >

        <action
            android:id="@+id/action_navigation_dashboard_to_lawsFilteredFragment"
            app:destination="@id/navigation_laws_filtered"
            />
        <action
            android:id="@+id/action_navigation_dashboard_to_navigation_home"
            app:destination="@id/navigation_home"
            app:popUpTo="@+id/navigation_dashboard"
            app:popUpToInclusive="true"
            />
        <action
            android:id="@+id/action_navigation_dashboard_to_navigation_notifications"
            app:destination="@id/navigation_notifications"
            app:popUpTo="@+id/navigation_dashboard"
            app:popUpToInclusive="true"
            />

    </fragment>

    <fragment
        android:id="@+id/navigation_notifications"
        android:name="ru.home.government.screens.tracker.TrackerFragment"
        android:label="@string/title_tracker"
        tools:layout="@layout/fragment_tracker">

        <action
            android:id="@+id/action_navigation_notifications_to_navigation_dashboard"
            app:destination="@id/navigation_dashboard"
            app:popUpTo="@+id/navigation_home"
            app:popUpToInclusive="true" />

    </fragment>

    <fragment
        android:id="@+id/navigation_laws_filtered"
        android:name="ru.home.government.screens.laws.filter.LawsFilteredFragment"
        android:label="@string/title_search"
        tools:layout="@layout/fragment_law_filtered">

        <argument
            android:name="EXTRA_KEY"
            app:argType="string"
            android:defaultValue="false" />

        <action
            android:id="@+id/action_navigation_laws_filtered_to_navigation_home"
            app:destination="@id/navigation_home"
            app:popUpTo="@+id/navigation_dashboard"
            app:popUpToInclusive="true" />

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

    </fragment>
</navigation>

直接通过监听BottomNavigationView的选中事件，结合Navigation组件的popBackStack()方法实现，完全符合Navigation规范，步骤如下：

1. 获取NavController和BottomNavigationView实例：

val navController = findNavController(R.id.nav_host_fragment)
val bottomNav = findViewById<BottomNavigationView>(R.id.bottom_nav_view)

2. 设置OnItemSelectedListener，在切换到非B标签时，检查当前栈顶是否是D页，若是则弹出栈回到B页：

bottomNav.setOnItemSelectedListener { item ->
    // 当选中的不是B标签时
    if (item.itemId != R.id.navigation_dashboard) {
        // 检查当前页面是否是搜索后的D页
        if (navController.currentDestination?.id == R.id.navigation_laws_filtered) {
            // 弹出栈到B页，false表示保留B页本身
            navController.popBackStack(R.id.navigation_dashboard, false)
        }
    }
    // 执行BottomNavigation默认的导航逻辑
    NavigationUI.onNavDestinationSelected(item, navController)
}

3. 额外优化：调整D页到A/C页的action配置，确保从D页直接切换标签时也能清除栈（将popUpToInclusive改为false，保留B页作为栈底，方便后续切回）：

<action
    android:id="@+id/action_navigation_laws_filtered_to_navigation_home"
    app:destination="@id/navigation_home"
    app:popUpTo="@+id/navigation_dashboard"
    app:popUpToInclusive="false" />

<action
    android:id="@+id/action_navigation_laws_filtered_to_navigation_notifications"
    app:destination="@id/navigation_notifications"
    app:popUpTo="@+id/navigation_dashboard"
    app:popUpToInclusive="false" />

这样处理后，只要用户离开B标签，不管是从B页还是D页切换，都会自动把D页从栈中移除，下次切回B标签时只会显示初始的B页，完全符合需求。

内容的提问来源于stack exchange，提问作者Gleichmut