无法在Google Map片段中获取当前位置

Question

I am trying to get current location in map fragment but the crashes with an error in line googleMap.setMyLocationEnabled(true); I used Location and Latlang to detect current location.

mapFragment.java

public class mapFragment extends Fragment {

    MapView mMapView;
    private GoogleMap googleMap;
    Location location;

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // inflat and return the layout
        View v = inflater.inflate(R.layout.fragment_map, container,
                false);
        mMapView = (MapView) v.findViewById(R.id.mapView);
        mMapView.onCreate(savedInstanceState);

        mMapView.onResume();// needed to get the map to display immediately

        try {
            MapsInitializer.initialize(getActivity().getApplicationContext());
        } catch (Exception e) {
            e.printStackTrace();
        }
        googleMap.setMyLocationEnabled(true);
        googleMap = mMapView.getMap();
        // latitude and longitude
        LatLng lat = new LatLng(location.getLatitude(), location.getLongitude());
        /*double latitude = 17.385044;
        double longitude = 78.486671;*/

        // create marker
        MarkerOptions marker = new MarkerOptions().position(
                lat).title("Hello Maps");

        // Changing marker icon
        marker.icon(BitmapDescriptorFactory
                .defaultMarker(BitmapDescriptorFactory.HUE_ROSE));

        // adding marker
        googleMap.addMarker(marker);
        CameraPosition cameraPosition = new CameraPosition.Builder()
                .target(lat).zoom(12).build();
        googleMap.animateCamera(CameraUpdateFactory
                .newCameraPosition(cameraPosition));

        // Perform any camera updates here
        return v;
    }


    @Override
    public void onResume() {
        super.onResume();
        mMapView.onResume();
    }

    @Override
    public void onPause() {
        super.onPause();
        mMapView.onPause();
    }

    @Override
    public void onDestroy() {
        super.onDestroy();
        mMapView.onDestroy();
    }

    @Override
    public void onLowMemory() {
        super.onLowMemory();
        mMapView.onLowMemory();
    }
}

fragment_map.xml

<?xml version="1.0" encoding="utf-8"?>
<com.google.android.gms.maps.MapView
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/mapView"
    android:layout_width="match_parent"
    android:layout_height="match_parent" />

Answer 1

Looks like you have a few issues, but the crash is happening because you need to call getMap() before you call setMyLocationEnabled() .

Change this:

googleMap.setMyLocationEnabled(true);
googleMap = mMapView.getMap();

...to this:

googleMap = mMapView.getMap();
googleMap.setMyLocationEnabled(true);

Updated: I was able to get this code working.

Getting the current location should be done with the Fused Location Provider API , but that is beyond the scope of this question.

The method in this sample code might work on older devices, but on 4.4.4 it's returning a null location due to getMyLocation() being depricated.

However, with the null check in place the map displays correctly, and you can click on the location button to have the map move to your current location.

        MapView mMapView;
        private GoogleMap googleMap;
        Location location;

        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container,
                                 Bundle savedInstanceState) {
            // inflat and return the layout
            View v = inflater.inflate(R.layout.fragment_main, container,
                    false);
            mMapView = (MapView) v.findViewById(R.id.mapView);
            mMapView.onCreate(savedInstanceState);

            mMapView.onResume();// needed to get the map to display immediately

            try {
                MapsInitializer.initialize(getActivity().getApplicationContext());
            } catch (Exception e) {
                e.printStackTrace();
            }
            googleMap = mMapView.getMap();
            googleMap.setMyLocationEnabled(true);

            location = googleMap.getMyLocation();

            if (location != null) {

                // latitude and longitude
                LatLng lat = new LatLng(location.getLatitude(), location.getLongitude());

                //double latitude = 17.385044;
                //double longitude = 78.486671;
                //LatLng lat = new LatLng(latitude,longitude);

                // create marker

                MarkerOptions marker = new MarkerOptions().position(
                        lat).title("Hello Maps");

                // Changing marker icon
                marker.icon(BitmapDescriptorFactory
                        .defaultMarker(BitmapDescriptorFactory.HUE_ROSE));

                // adding marker
                googleMap.addMarker(marker);

                CameraPosition cameraPosition = new CameraPosition.Builder()
                        .target(lat).zoom(12).build();


                googleMap.animateCamera(CameraUpdateFactory
                        .newCameraPosition(cameraPosition));

            }

            // Perform any camera updates here
            return v;
        }

Answer 2

You can use the setOnMyLocationChangeListener method to get the current location. Download the source here( Show Google Map In Android )

MainActivity.Java

package deepshikha.googlemap;

import android.Manifest;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.location.Location;
import android.support.v4.app.ActivityCompat;
import android.support.v4.content.ContextCompat;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;

import com.google.android.gms.maps.CameraUpdateFactory;
import com.google.android.gms.maps.GoogleMap;
import com.google.android.gms.maps.MapFragment;
import com.google.android.gms.maps.model.LatLng;
import com.google.android.gms.maps.model.MarkerOptions;

public class MainActivity extends AppCompatActivity {
public GoogleMap googleMap;
private static final int REQUEST_PERMISSIONS = 100;
Button btn;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    btn = (Button)findViewById(R.id.btn);


    fn_permission();
    fn_currentlocation ();
}

public void fn_currentlocation (){

    if (googleMap == null) {
        googleMap = ((MapFragment) getFragmentManager().findFragmentById(R.id.map)).getMap();

        try {

            googleMap.setMyLocationEnabled(true);
        } catch (Exception e) {

        }

        if (googleMap != null) {

            googleMap.setOnMyLocationChangeListener(new GoogleMap.OnMyLocationChangeListener() {

                @Override
                public void onMyLocationChange(Location arg0) {
                    // TODO Auto-generated method stub
                    double current_latitude = arg0.getLatitude();
                    double currrent_longitude = arg0.getLongitude();
                    LatLng current_latLng = new LatLng(current_latitude, currrent_longitude);
                    googleMap.moveCamera(CameraUpdateFactory.newLatLng(current_latLng));

                    Log.e("CURRENT LONGITUDE", currrent_longitude + "");
                    Log.e("CURRENT LATITUDE", current_latitude + "");

                    googleMap.animateCamera(CameraUpdateFactory.zoomTo(15));
                    googleMap.addMarker(new MarkerOptions().position(current_latLng).title("Marker"));
                }
            });

        }


    }
}

private void fn_permission(){
    if ((ContextCompat.checkSelfPermission(getApplicationContext(), Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED) ||
            (ContextCompat.checkSelfPermission(getApplicationContext(), Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED)) {
        if ((ActivityCompat.shouldShowRequestPermissionRationale(MainActivity.this, Manifest.permission.ACCESS_FINE_LOCATION)) &&
                (ActivityCompat.shouldShowRequestPermissionRationale(MainActivity.this, Manifest.permission.ACCESS_COARSE_LOCATION))) {
        } else {
            ActivityCompat.requestPermissions(MainActivity.this,
                    new String[]{Manifest.permission.ACCESS_FINE_LOCATION,Manifest.permission.ACCESS_COARSE_LOCATION},
                    REQUEST_PERMISSIONS);
        }
    }

}


@Override
public void onRequestPermissionsResult(int requestCode, String[] permissions, int[] grantResults) {
    super.onRequestPermissionsResult(requestCode, permissions, grantResults);

    switch (requestCode) {
        case REQUEST_PERMISSIONS: {
            for (int i = 0; i < grantResults.length; i++) {
                if (grantResults.length > 0 && grantResults[i] == PackageManager.PERMISSION_GRANTED) {

                } else {
                    Toast.makeText(MainActivity.this, "The app was not allowed to read or write to your storage. Hence, it cannot function properly. Please consider granting it this permission", Toast.LENGTH_LONG).show();
                }
            }
        }
    }
}
}