单Activity设计时如何隐藏底栏导航？

Question

我试图仅在几个片段中显示底部栏导航（即，为我的大部分片段隐藏它）..

我读了 official document about this, but it unclear to me, like where do I put the code, and I read ，比如“我很惊讶文档中有这样的建议，因为它实际上看起来很糟糕，因为侦听器会在新片段放置在屏幕上之前触发，导致可见的闪烁（有时存在，有时不存在）”。

我对此进行了研究，根据我的理解，我需要创建一个嵌套的 naviagtion_graph（导航）或其他内容，听取 onDestinationChanged 并将底部导航或工具栏设置为 Gone..

我不是很明白这个..我只是想在大多数片段中隐藏底部导航栏..

这是我的 navigation_gragh (mobile_navigation) :

<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.testingbottomnav.ui.home.HomeFragment"
        android:label="@string/title_home"
        tools:layout="@layout/fragment_home" >
        <action
            android:id="@+id/action_navigation_home_to_newScreenFragment"
            app:destination="@id/newScreenFragment" />
    </fragment>

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

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

这是我的 activity_main.xml :

<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_marginStart="0dp"
        android:layout_marginEnd="0dp"
        android:background="?android:attr/windowBackground"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:labelVisibilityMode="selected"
        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>

这是我的 MainActivty.kt :

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)
    }
}

任何帮助将不胜感激，谢谢..

Answer 1

首先设置导航，然后将目的地更改侦听器添加到导航控制器。每当您导航到片段 navController.navigate(/* Some Destination Id */) 时，目标更改侦听器就会在那里启动，您可以检查并比较是否要显示或隐藏底部导航或工具栏。

private fun setupBottomNavigation() {

        val navHostFragment = supportFragmentManager
            .findFragmentById(R.id.fragment_container_view) as NavHostFragment?

        if (navHostFragment != null) {

            navController = navHostFragment.navController

            setupWithNavController(binding!!.navView, navController!!)

            initDestinationListener()

        }
    }

    private fun initDestinationListener() {

        navController!!.addOnDestinationChangedListener { controller: NavController?, destination: NavDestination, bundle: Bundle? ->

            // Showing or Hiding Bottom Navigation on Specific Screen
            
            if (destination.id == R.id.navigation_plan ||
                destination.id == R.id.navigation_video ||
                destination.id == R.id.navigation_about ||
                destination.id == R.id.navigation_detail ||
                destination.id == R.id.navigation_contact ||
                destination.id == R.id.navigation_privacy ||
                destination.id == R.id.navigation_comments
            ) {

                hideBottomNavigation()

            } else {

                showBottomNavigation()

            }
        }
    }

Answer 2

我在 onCreate 方法中添加了这行代码：

// hiding bottom bar
    navController.addOnDestinationChangedListener { _, nd: NavDestination, _ ->
        // the IDs of fragments as defined in the `navigation_graph`
        if (nd.id == R.id.navigation_home || nd.id == R.id.navigation_dashboard
            || nd.id == R.id.navigation_notifications
        ) {
            navView.visibility = View.VISIBLE
        } else {
            navView.visibility = View.GONE
        }
    }

Answer 3

如果您想让您的 BottomNavigationView 仅在目标是顶级目标时可见，您可以尝试：

 val appBarConfiguration = AppBarConfiguration(
            setOf(
                R.id.navigation_home, 
                R.id.navigation_dashboard, 
                R.id.navigation_notifications
            )
        )
 navController.addOnDestinationChangedListener { controller: NavController, destination: NavDestination, bundle: Bundle? ->
 yourBottomNavigationView.isVisible = appBarConfiguration.topLevelDestinations.contains(destination.id)
}

Answer 4

您可以编写一个方法来在 activity 中初始化导航并在此方法中隐藏导航并在 onCreate() 中使用它，如下所示：

 private fun setupNavigation() {
    val navController = findNavController(R.id.nav_host_fragment_activity_main)
    navView.setupWithNavController(navController)
    navController.addOnDestinationChangedListener { controller, destination, arguments ->
        when (destination.id) {
            R.id.fragment1 -> bottomNavigation.visibility = View.VISIBLE
            R.id.fragment2 -> bottomNavigation.visibility = View.VISIBLE
            R.id.fragment3 -> bottomNavigation.visibility = View.VISIBLE
            else -> bottomNavigation.visibility = View.GONE
        }
    }
}

此代码在片段 1、2、3 中显示导航并在另一个片段中隐藏它

单Activity设计时如何隐藏底栏导航？

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