谷歌地图未显示在底部导航中，Andriod studio (java) 中的活动

如何解决谷歌地图未显示在底部导航中，Andriod studio (java) 中的活动

左下角有GOOGLE图标，但地图不显示。

(1)strings.xml

（我在里面写了 api）

这个api可以用，我在其他项目也用了同一套api，但是这里加了就显示不出来了。

<resources>
<string name="app_name">HIKING</string>
<string name="map_key" translatable="false">AIza.....</string>

(2) AndroidManifest.xml

<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />

<application
    android:allowBackup="true"
    android:icon="@mipmap/ic_launcher"
    android:label="@string/app_name"
    android:roundIcon="@mipmap/ic_launcher_round"
    android:supportsRtl="true"
    android:theme="@style/AppTheme">

    <Meta-data
        android:name="com.google.android.geo.API_KEY"
        android:value="@string/map_key" />

(3)activity_main.xml (使用RelativeLayout)

//navigation
<com.google.android.material.bottomnavigation.BottomNavigationView
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:id="@+id/bottom_navigation"
    app:itemBackground="@color/colorPrimary"
    app:itemTextColor="@drawable/selector"
    app:itemIconTint="@drawable/selector"
    app:menu="@menu/menu_navigation"
    android:layout_alignParentBottom="true" />

这是关于地图。

<fragment
    android:layout_width="match_parent"
    android:layout_height="600dp"
    android:layout_marginTop="60dp"
    android:id="@+id/google_map"
    android:name="com.google.android.gms.maps.SupportMapFragment"/>

(4)MainActivity.java

public class MainActivity extends FragmentActivity implements OnMapReadyCallback {

GoogleMap googleMap;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    SupportMapFragment mapFragment = (SupportMapFragment) getSupportFragmentManager()
            .findFragmentById(R.id.google_map);
    mapFragment.getMapAsync(this);


    //navigation
    BottomNavigationView bottomNavigationView = findViewById(R.id.bottom_navigation);
    bottomNavigationView.setSelectedItemId(R.id.map);
    bottomNavigationView.setonNavigationItemSelectedListener(new BottomNavigationView.OnNavigationItemSelectedListener() {
        @Override
        public boolean onNavigationItemSelected(@NonNull MenuItem menuItem) {
            switch (menuItem.getItemId()){
                case R.id.map:
                    return true;

                case R.id.mountains:
                    startActivity(new Intent(getApplicationContext(),Mountain.class));
                    overridePendingTransition(0,0);
                    return true;

                case R.id.watch:
                    startActivity(new Intent(getApplicationContext(),Watch.class));
                    overridePendingTransition(0,0);
                    return true;

                case R.id.account:
                    startActivity(new Intent(getApplicationContext(),Account.class));
                    overridePendingTransition(0,0);
                    return true;

            }
            return false;
        }
    });
}

以及更多代码。

@Override
public void onMapReady(GoogleMap Map) {
    googleMap = Map;

    googleMap.setonMapClickListener(new GoogleMap.OnMapClickListener() {
        @Override
        public void onMapClick(LatLng latLng) {
            MarkerOptions markerOptions = new MarkerOptions();
            markerOptions.position(latLng);
            //set latitude and longitudue on marker
            markerOptions.title(latLng.latitude+" : "+latLng.longitude);
            googleMap.clear();
            //zoom on marker
            googleMap.animateCamera(CameraUpdateFactory.newLatLngZoom(latLng,10));
            //add marker on map
            googleMap.addMarker(markerOptions);


        }
    });

}