谷歌地图在Android应用程序中不可见

Question

我使用此代码在地图上显示我的位置，但地图在应用中不可见。应用运行正常。我不知道自己做错了什么。请帮帮我。谢谢。

public class MapsActivity extends FragmentActivity implements LocationListener,OnMapReadyCallback{

GoogleMap mMap;
LatLng myPosition;

Location location;
LocationManager locationManager;
double latitude = 0, longitude = 0;
/**
 * ATTENTION: This was auto-generated to implement the App Indexing API.
 * See https://g.co/AppIndexing/AndroidStudio for more information.
 */
private GoogleApiClient client;

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

    // Obtain the SupportMapFragment and get notified when the map is ready      to be used.
    SupportMapFragment mapFragment = (SupportMapFragment) getSupportFragmentManager()
            .findFragmentById(R.id.map);
   // mMap = mapFragment.getMap();
    mapFragment.getMapAsync(this);

}

@Override
public void onMapReady(GoogleMap mMap) {




    if (ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
        // TODO: Consider calling
        //    ActivityCompat#requestPermissions
        // here to request the missing permissions, and then overriding
        //   public void onRequestPermissionsResult(int requestCode, String[] permissions,
        //                                          int[] grantResults)
        // to handle the case where the user grants the permission. See the documentation
        // for ActivityCompat#requestPermissions for more details.
        return;
    }
    mMap.setMyLocationEnabled(true);

    locationManager = (LocationManager) getSystemService(LOCATION_SERVICE);


    Criteria criteria = new Criteria();
    criteria.setAccuracy(Criteria.ACCURACY_FINE);

    // getting GPS status
    boolean isGPSEnabled = locationManager.isProviderEnabled(LocationManager.GPS_PROVIDER);

    // getting network status
    boolean isNetworkEnabled = locationManager.isProviderEnabled(LocationManager.NETWORK_PROVIDER);

    if (!isGPSEnabled && !isNetworkEnabled) {
        AlertDialog.Builder alertDialog=new AlertDialog.Builder(this);
        alertDialog.setTitle("GPS Is Off");

        alertDialog.setMessage("Please Enable GPS for better Location");

        alertDialog.setPositiveButton("YES", new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface dialog, int which) {
                Intent i = new Intent(Settings.ACTION_LOCATION_SOURCE_SETTINGS);
                startActivity(i);
            }
        });

        alertDialog.setNegativeButton("NO", new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface dialog, int which) {

            }
        });

        alertDialog.show();

    }

    {

        if (isNetworkEnabled) {
            locationManager.requestLocationUpdates(LocationManager.NETWORK_PROVIDER, 1000, 100f, this);

            if (locationManager != null) {
                location = locationManager.getLastKnownLocation(LocationManager.NETWORK_PROVIDER);
                if (location != null) {
                    latitude = location.getLatitude();
                    longitude = location.getLongitude();
                }
            }
        }
        // if GPS Enabled get lat/long using GPS Services
        if (isGPSEnabled) {
            if (location == null) {
                locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 1000L, 100f, this);
                if (locationManager != null) {
                    location = locationManager.getLastKnownLocation(LocationManager.GPS_PROVIDER);
                    if (location != null) {
                        latitude = location.getLatitude();
                        longitude = location.getLongitude();

                    }
                }
            }
        }
    }
  /*  String provider = locationManager.getBestProvider(criteria, true).toString();
   locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 1000L, 100.0f, this);
  //   locationManager.requestLocationUpdates(provider, 1000, 10f, this);
    location = locationManager.getLastKnownLocation(provider);*/

//Toast.makeText(getApplicationContext(),provider,Toast.LENGTH_LONG).show();


    if (location != null) {
        onLocationChanged(location);
    }

    // latitude = location.getLatitude();

//      longitude = location.getLongitude();


    myPosition = new LatLng(latitude, longitude);
    mMap.addMarker(new MarkerOptions().position(myPosition));

    mMap.animateCamera(CameraUpdateFactory.newLatLngZoom(new LatLng(latitude, longitude), 16));





    Timer t = new Timer(false);   //To show text for required time

    t.schedule(new TimerTask() {
        @Override
        public void run() {
            runOnUiThread(new Runnable() {

                public void run() {

                    dialogbox();

                }
            });
        }
    }, 10000);


}
}

还有mMap.getMyType给出＆＃39; 1＆＃39;值表示法线贴图。但地图不可见。此外，我将纬度和经度值传递给另一个活动。在该活动中，它将打印所提供的纬度和经度的地址。这部分工作正常，这意味着应用程序正确定位我的位置，但地图不可见。