我有一个底部导航视图，我在我的应用程序中实现了它。它有3个图标：

这就是我的MapsActivity的样子

所以我已经设法显示片段A和B。但是看起来我在xml中的某个地方用片段搞砸了（我是新来的，所以我仍然试图围绕xmls的布局进行思考），如果我点击屏幕顶部的搜索栏来自MapsActivity，那么搜索栏将显示为我的片段是“透明的”，但是你实际上看不到片段上的搜索栏。

activity_maps. xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
                xmlns:app="http://schemas.android.com/apk/res-auto"
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:orientation="vertical"
                android:id="@+id/fragmentContainer">

    <fragment
            android:id="@+id/place_autocomplete_fragment"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:name="com.google.android.gms.location.places.ui.PlaceAutocompleteFragment"
    />
    <fragment xmlns:android="http://schemas.android.com/apk/res/android"
              xmlns:tools="http://schemas.android.com/tools"
              android:layout_width="match_parent"
              android:layout_height="match_parent"
              android:id="@+id/map"
              tools:context=".MapsActivity"
              android:name="com.google.android.gms.maps.SupportMapFragment"
              android:layout_below="@id/place_autocomplete_fragment"
              android:layout_above="@id/bottom_navigation"
    />
    <android.support.design.widget.BottomNavigationView
            android:id="@+id/bottom_navigation"
            app:menu="@menu/bottom_nav_menu"
            android:background="@color/colorPrimaryDark"
            android:layout_width="match_parent"
            app:itemIconTint="@color/common_google_signin_btn_text_dark_default"
            android:layout_height="wrap_content"
            android:layout_alignParentBottom="true" android:layout_marginBottom="0dp"
            android:layout_alignParentLeft="true" android:layout_marginLeft="0dp"
            android:layout_alignParentStart="true" android:layout_marginStart="0dp"/>
</RelativeLayout>

fragment_a. xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
              android:layout_width="match_parent"
              android:layout_height="match_parent"
              android:orientation="vertical"
              android:background="@color/common_google_signin_btn_text_dark_pressed">

    <TextView
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:text="Fragment A"
            android:gravity="center_vertical|center_horizontal"/>

</LinearLayout>

我在MapsActivity. kt中这样显示我的片段。

class MapsActivity : AppCompatActivity(), OnMapReadyCallback {
        private val mOnNavigationItemSelectedListener = BottomNavigationView.OnNavigationItemSelectedListener {item->
        when(item.itemId){
            R.id.nav_map -> {
                Log.d(TAG, "map pressed")
                // if there's a fragment, close it

                return@OnNavigationItemSelectedListener true
            }
            R.id.nav_A -> {
                Log.d(TAG, "fragment A pressed")
                replaceFragment(FragmentA())
                return@OnNavigationItemSelectedListener true
            }
            R.id.nav_B -> {
                Log.d(TAG, "fragment B pressed")
                replaceFragment(FragmentB())
                return@OnNavigationItemSelectedListener true
            }
        }
        false
    }    

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_maps)
        val mapFragment = supportFragmentManager
            .findFragmentById(R.id.map) as SupportMapFragment
        mapFragment.getMapAsync(this)

        val bottomNavigation: BottomNavigationView = findViewById(R.id.bottom_navigation)
        bottomNavigation.setOnNavigationItemSelectedListener(mOnNavigationItemSelectedListener)
}

    private fun replaceFragment(fragment: Fragment){
        val fragmentTransaction = supportFragmentManager.beginTransaction()

        fragmentTransaction.replace(R.id.fragmentContainer, fragment)
        fragmentTransaction.commit()
    }
...
...
}

另一个问题，我有，我将解决后，我固定这篇文章的问题，但有人知道如何关闭当前片段时，我点击地图活动图标在导航栏？