android - BottomNavigationView.setupWithNavController 不工作

Question

目前我正在开发一个 Android 应用程序，我想在其中同时使用 Android Navigation Component和 BottomNavigationView .
在开发上述应用程序时，我查看了 官方codelab 还有几个问题，但事实证明它们没有任何帮助。
问题是分配 navController给我的BottomNavigationView似乎没有任何效果——点击菜单项不会影响导航主机。
我的代码:
main_activity.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.coordinatorlayout.widget.CoordinatorLayoutxmlns: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=".MainActivity">

    <androidx.fragment.app.FragmentContainerView
        android:id="@+id/main_host_fr"
        android:name="androidx.navigation.fragment.NavHostFragment"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        app:defaultNavHost="true"
        app:navGraph="@navigation/nav_graph" />

    <com.google.android.material.bottomnavigation.BottomNavigationView
        android:id="@+id/main_nav_bnv"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_gravity="bottom"
        android:background="@android:color/transparent"
        android:elevation="0dp"
        app:elevation="0dp"
        app:menu="@menu/menu_main" />

</androidx.coordinatorlayout.widget.CoordinatorLayout>

MainActivity.kt

import android.os.Bundle
import android.os.PersistableBundle
import android.view.MenuItem
import androidx.appcompat.app.AppCompatActivity
import androidx.navigation.findNavController
import androidx.navigation.fragment.NavHostFragment
import androidx.navigation.ui.NavigationUI
import androidx.navigation.ui.setupWithNavController
import com.aredruss.qurio.databinding.ActivityMainBinding
import com.aredruss.qurio.helpers.viewBinding

class MainActivity : AppCompatActivity() {

    // ViewBindingDelegate
    private val binding: ActivityMainBinding by viewBinding(ActivityMainBinding::inflate)

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
    
    }

    // Using onPostCreate because accessing NavHost in OnCreate causes crashes
    override fun onPostCreate(savedInstanceState: Bundle?, persistentState: PersistableBundle?) {
        super.onPostCreate(savedInstanceState, persistentState)
        binding.navigationBb.setupWithNavController(findNavController(R.id.main_host_fr))
        NavigationUI.setupWithNavController(binding.mainNavBnv, findNavController(R.id.main_host_fr))
    }
}

nav_graph.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/nav_graph"
    app:startDestination="@id/action_history">

    <fragment
        android:id="@+id/action_history"
        android:name="com.aredruss.qurio.ui.HistoryFragment"
        android:label="HistoryFragment"
        tools:layout="@layout/fragment_history" >
    </fragment>
  
    <fragment
        android:id="@+id/action_settings"
        android:name="com.aredruss.qurio.ui.SettingsFragment"
        android:label="SettingsFragment"
        tools:layout="@layout/fragment_settings" >
    </fragment>
</navigation>

menu_main.xml

<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto">
    <item
        android:id="@+id/action_history"
        android:icon="@drawable/ic_history"
        android:title="History"
        app:showAsAction="withText" />

    <item
        android:id="@+id/action_settings"
        android:title="Settings"
        android:icon="@drawable/ic_settings"
        app:showAsAction="withText"
        />
</menu>

我已经 checkout this解决方案，它没有任何帮助。

Answer 1

你覆盖了错误的onPostCreate() :

override fun onPostCreate(savedInstanceState: Bundle?, persistentState: PersistableBundle?) {

你不想要带 PersistableBundle 的那个。 - 你想要普通的:

override fun onPostCreate(savedInstanceState: Bundle?) {

现在您的 onPostCreate()实际上会被调用。
当然，你不应该使用 onPostCreate()一点也不。相反，您应该是 following the documentation ，其中明确指出您应该使用以下代码来获取您的 NavController在 onCreate() :

val navHostFragment =
    supportFragmentManager.findFragmentById(R.id.main_host_fr) as NavHostFragment
val navController = navHostFragment.navController

这使您可以将整个代码编写为:

// ViewBindingDelegate
private val binding: ActivityMainBinding by viewBinding(ActivityMainBinding::inflate)

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    // Note how we actually set the content view from the binding
    setContentView(binding.root)

    val navHostFragment =
        supportFragmentManager.findFragmentById(R.id.main_host_fr) as NavHostFragment
    val navController = navHostFragment.navController

    binding.navigationBb.setupWithNavController(navController)
    binding.mainNavBnv.setupWithNavController(navController)
}