BottomNavigationView 的导航错误

Question

我的 BottomNavigationView 导航无法正常工作，我很困惑。

• 当我第一次打开该应用程序时，它运行良好。我单击 BottomNavigationView 中的按钮，然后显示相应的片段。
• 使用片段 A 上的“转到 B”按钮从片段 A 导航到片段 B 后，我开始看到该错误。从那时起，当我单击 BottomNavigationView 中的 A 按钮时，将显示 B。

我尝试过的事情：

• 我覆盖了 A 中的所有片段生命周期回调（onCreate()、onCreateView()、onViewCreated()、onViewStateRestored()、onStart()、onResume()）。我在每个中都放置了断点。当处于越野车状态时，没有人被击中。
• 我使用底部导航活动的 Android 模板创建了一个新应用程序，并在那里重现了该错误。我唯一改变的是在片段 A 上添加一个导航到片段 B 的按钮。

我对 Android 和堆栈溢出都很陌生，所以如果我做了什么愚蠢的事情，请告诉我。预先感谢您的任何帮助！

这是重现该错误的代码。 （片段 A 是 HomeFragment）

HomeFragment.ktfragment_home.xml

import android.os.Bundle
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import android.widget.TextView
import androidx.fragment.app.Fragment
import androidx.lifecycle.ViewModelProvider
import androidx.navigation.findNavController
import androidx.navigation.fragment.findNavController
import com.example.myapplication.R
import com.example.myapplication.databinding.FragmentHomeBinding

class HomeFragment : Fragment() {

    private var _binding: FragmentHomeBinding? = null

    // This property is only valid between onCreateView and
    // onDestroyView.
    private val binding get() = _binding!!

    override fun onCreateView(
        inflater: LayoutInflater,
        container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View {
        val homeViewModel =
            ViewModelProvider(this).get(HomeViewModel::class.java)

        _binding = FragmentHomeBinding.inflate(inflater, container, false)
        val root: View = binding.root

        val textView: TextView = binding.textHome
        homeViewModel.text.observe(viewLifecycleOwner) {
            textView.text = it
        }
        return root
    }

    // This is the code I added
    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)

        binding.button.setOnClickListener {view ->
            view.findNavController().navigate(HomeFragmentDirections.actionNavigationHomeToNavigationDashboard())
        }
    }

    override fun onDestroyView() {
        super.onDestroyView()
        _binding = null
    }
}

mobile_navigation.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"
    tools:context=".ui.home.HomeFragment">

    <TextView
        android:id="@+id/text_home"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginEnd="8dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="8dp"
        android:textAlignment="center"
        android:textSize="20sp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <!-- I added this button -->
    <Button
        android:id="@+id/button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Dashboard"
        app:layout_constraintTop_toBottomOf="@id/text_home"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"/>
</androidx.constraintlayout.widget.ConstraintLayout>

顶级

<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_home">

    <fragment
        android:id="@+id/navigation_home"
        android:name="com.example.myapplication.ui.home.HomeFragment"
        android:label="@string/title_home"
        tools:layout="@layout/fragment_home" >
        <!-- I added this action -->
        <action
            android:id="@+id/action_navigation_home_to_navigation_dashboard"
            app:destination="@id/navigation_dashboard" />
    </fragment>

    <fragment
        android:id="@+id/navigation_dashboard"
        android:name="com.example.myapplication.ui.dashboard.DashboardFragment"
        android:label="@string/title_dashboard"
        tools:layout="@layout/fragment_dashboard" />

    <fragment
        android:id="@+id/navigation_notifications"
        android:name="com.example.myapplication.ui.notifications.NotificationsFragment"
        android:label="@string/title_notifications"
        tools:layout="@layout/fragment_notifications" />
</navigation>

MainActivity.kt（未修改此）

package com.example.myapplication

import android.os.Bundle
import com.google.android.material.bottomnavigation.BottomNavigationView
import androidx.appcompat.app.AppCompatActivity
import androidx.navigation.findNavController
import androidx.navigation.ui.AppBarConfiguration
import androidx.navigation.ui.setupActionBarWithNavController
import androidx.navigation.ui.setupWithNavController
import com.example.myapplication.databinding.ActivityMainBinding

class MainActivity : AppCompatActivity() {

    private lateinit var binding: ActivityMainBinding

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

        binding = ActivityMainBinding.inflate(layoutInflater)
        setContentView(binding.root)

        val navView: BottomNavigationView = binding.navView

        val navController = findNavController(R.id.nav_host_fragment_activity_main)
        // Passing each menu ID as a set of Ids because each
        // menu should be considered as top level destinations.
        val appBarConfiguration = AppBarConfiguration(
            setOf(
                R.id.navigation_home, R.id.navigation_dashboard, R.id.navigation_notifications
            )
        )
        setupActionBarWithNavController(navController, appBarConfiguration)
        navView.setupWithNavController(navController)
    }
}

activity_main.xml（未修改此）

<?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"
    android:id="@+id/container"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingTop="?attr/actionBarSize">

    <com.google.android.material.bottomnavigation.BottomNavigationView
        android:id="@+id/nav_view"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginEnd="0dp"
        android:layout_marginStart="0dp"
        android:background="?android:attr/windowBackground"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:menu="@menu/bottom_nav_menu" />

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

</androidx.constraintlayout.widget.ConstraintLayout>

build.gradle

// Top-level build file where you can add configuration options common to all sub-projects/modules.

// I added everything within the buildscript block
buildscript {
    repositories {
        google()
    }
    dependencies {
        classpath("androidx.navigation:navigation-safe-args-gradle-plugin:2.4.1")
    }
}

plugins {
    id 'com.android.application' version '7.1.2' apply false
    id 'com.android.library' version '7.1.2' apply false
    id 'org.jetbrains.kotlin.android' version '1.6.10' apply false
}

task clean(type: Delete) {
    delete rootProject.buildDir
}

build.gradle（应用程序）

plugins {
    id 'com.android.application'
    id 'org.jetbrains.kotlin.android'
    // I added this line
    id 'androidx.navigation.safeargs.kotlin'
}

android {
    compileSdk 31

    defaultConfig {
        applicationId "com.example.myapplication"
        minSdk 26
        targetSdk 31
        versionCode 1
        versionName "1.0"

        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
    }

    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
        }
    }
    compileOptions {
        sourceCompatibility JavaVersion.VERSION_1_8
        targetCompatibility JavaVersion.VERSION_1_8
    }
    kotlinOptions {
        jvmTarget = '1.8'
    }
    buildFeatures {
        viewBinding true
    }
}

dependencies {

    implementation 'androidx.core:core-ktx:1.7.0'
    implementation 'androidx.appcompat:appcompat:1.4.1'
    implementation 'com.google.android.material:material:1.5.0'
    implementation 'androidx.constraintlayout:constraintlayout:2.1.3'
    implementation 'androidx.lifecycle:lifecycle-livedata-ktx:2.4.1'
    implementation 'androidx.lifecycle:lifecycle-viewmodel-ktx:2.4.1'
    implementation 'androidx.navigation:navigation-fragment-ktx:2.4.1'
    implementation 'androidx.navigation:navigation-ui-ktx:2.4.1'
    testImplementation 'junit:junit:4.13.2'
    androidTestImplementation 'androidx.test.ext:junit:1.1.3'
    androidTestImplementation 'androidx.test.espresso:espresso-core:3.4.0'
}

Answer 1

我想通了。解决方法是将最后三行添加到 mobile_navigation.xml 中的操作标记中：

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

有关其工作原理的更多信息：https://developer.android.com/guide/navigation/multi-back-stacks#nav-xml

Answer 2

我已经寻找了很多解决这个问题的方法，但没有一个对我有用。
最后，我找到了一个可以“修复”这个“bug”的懒惰黑客。我已经测试了这个解决方案一段时间，到目前为止还没有发现任何问题。

注意：这不是解决此问题的官方方法。我建议不要使用此解决方案，直到所有解决方案都不适合您。

解决方案：

将此行：替换

navController.navigate(R.id.navigation_dashboard);

为此行：

findViewById(R.id.nav_view).findViewById(R.id.navigation_dashboard).performClick();

R.id.nav_view is BottomNavigationView 组件的 id。它可能位于您的 activity_main.xml 中。

R.id.navigation_dashboard 是您要导航到的片段的 id。它可能位于您的 res/navigation/mobile_navigation.xml 或 res/navigation/nav_graph.xml 中。