Android BottomNavigationView被删除/隐藏后保留空白 [英] Android BottomNavigationView leave blank space after being removed/hidden

问题描述

如果用户未通过身份验证，则转到登录"片段；如果用户通过身份验证，则转到主页"片段.当未经身份验证的用户打开应用程序时，bottomNavView应该被隐藏，但是它留下了空白.

When user in not authenticate, it goes to Login fragment, if he's authenticate it goes to home fragment. When unauthenticated user open the app, the bottomNavView should be hidden, it is but it leaves a blank space.

class MainActivity : AppCompatActivity() {

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

    val navigationController = findNavController(R.id.nav_host_fragment)
    val bottomNavigationView = findViewById<BottomNavigationView>(R.id.bottom_nav)

    findNavController(R.id.nav_host_fragment).addOnNavigatedListener { _, destination ->
        when (destination.id) {
            R.id.register1Fragment -> hideBottomNavigation()
            R.id.register2Fragment -> hideBottomNavigation()
            R.id.loginFragment -> hideBottomNavigation()
            else -> showBottomNavigation()
        }
    }

    NavigationUI.setupWithNavController(bottomNavigationView, navigationController)

    // Sets up the Toolbar actions (like Back Button) to be managed by the Navigation Component
    NavigationUI.setupActionBarWithNavController(this, navigationController)
}

private fun hideBottomNavigation() {
    // bottom_navigation is BottomNavigationView
    with(bottom_nav) {
        if (visibility == View.VISIBLE) {
            visibility = View.INVISIBLE

        }
    }
}

private fun showBottomNavigation() {
    // bottom_navigation is BottomNavigationView
    with(bottom_nav) {
        visibility = View.VISIBLE
    }
}

override fun onSupportNavigateUp() = findNavController(R.id.nav_host_fragment).navigateUp()
}

这是for主要活动的xml.那显示了bottomNavView是如何实现的.根viewGroup是ConstraintLayout，高度和宽度设置为match_parent.我很难弄清楚真正的问题在哪里.

Here's the xml for the for main activity. That show how the bottomNavView is implemented. The root viewGroup is a ConstraintLayout, height and width are set to match_parent. I had a hard time figuring out where the real problem is.

<fragment
    android:id="@+id/nav_host_fragment"
    android:name="androidx.navigation.fragment.NavHostFragment"
    app:navGraph="@navigation/main_navigation_graph"
    app:defaultNavHost="true"

    android:layout_width="match_parent"
    android:layout_height="0dp"
    app:layout_constraintBottom_toTopOf="@+id/bottom_nav"
    app:layout_constraintLeft_toLeftOf="parent"
    app:layout_constraintRight_toRightOf="parent"
    app:layout_constraintTop_toTopOf="parent" />


<com.google.android.material.bottomnavigation.BottomNavigationView
    android:id="@+id/bottom_nav"
    style="@style/Widget.MaterialComponents.BottomNavigationView.Colored"
    android:layout_width="0dp"
    android:layout_height="wrap_content"
    app:labelVisibilityMode="unlabeled"
    android:background="@color/colorPrimary"
    app:itemBackground="@color/bottom_nav_state"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintLeft_toLeftOf="parent"
    app:layout_constraintRight_toRightOf="parent"
    app:menu="@menu/menu_bottom_nav" />

推荐答案

更改为

private fun hideBottomNavigation() {
    // bottom_navigation is BottomNavigationView
    with(bottom_nav) {
        if (visibility == View.VISIBLE) {
            visibility = View.GONE

        }
    }
}

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