使用GPS GPS获取我当前的位置

Question

Hi I'm trying to get my location and use it to draw a path between my place and a specific location , I use GMapV2Direction class to draw the directions and this is my code

public class MapsActivity extends FragmentActivity implements LocationListener {
GoogleMap mMap;
Location location;
String provider;
LocationManager service;
GMapV2Direction md;
private Boolean flag = false;
LatLng fromPosition ;
LatLng toPosition = new LatLng(35.407838, 8.112893);

public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    flag = displayGpsStatus();
    if (!flag) {
        alertbox("Gps Status!!", "Your GPS is: OFF");
    }

    setContentView(R.layout.activity_maps);
    if (android.os.Build.VERSION.SDK_INT > 9) {
        StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build();
        StrictMode.setThreadPolicy(policy);
    }
    md = new GMapV2Direction();
    mMap = ((SupportMapFragment)getSupportFragmentManager()
            .findFragmentById(R.id.map)).getMap();

    service = (LocationManager)this.getSystemService(LOCATION_SERVICE);
    Criteria criteria = new Criteria();
    provider = service.getBestProvider(criteria, true);
    location = service.getLastKnownLocation(provider);
    if (location != null){
        fromPosition = new LatLng(location.getLatitude(), location.getLongitude());
        DrawRoute();
    }
    else{
       ProgressDialog mProgressDialog = new ProgressDialog(MapsActivity.this);

        mProgressDialog.setTitle("Waiting");

        mProgressDialog.setMessage("Loading...");
        mProgressDialog.setIndeterminate(false);

       mProgressDialog.show();

    }
}
/*----Method to Check GPS is enable or disable ----- */
private Boolean displayGpsStatus() {
    ContentResolver contentResolver = getBaseContext()
            .getContentResolver();
    boolean gpsStatus = Settings.Secure
            .isLocationProviderEnabled(contentResolver,
                    LocationManager.GPS_PROVIDER);
    if (gpsStatus) {
        return true;

    } else {
        return false;
    }
}
/*----------Method to create an AlertBox ------------- */
protected void alertbox(String title, String mymessage) {
    AlertDialog.Builder builder = new AlertDialog.Builder(this);
    builder.setMessage("Your Device's GPS is Disable")
            .setCancelable(false)
            .setTitle("** Gps Status **")
            .setPositiveButton("Gps On",
                    new DialogInterface.OnClickListener() {
                        public void onClick(DialogInterface dialog, int id) {
                            // finish the current activity
                            // AlertBoxAdvance.this.finish();
                            Intent myIntent = new Intent(
                                    Settings.ACTION_LOCATION_SOURCE_SETTINGS);
                            startActivity(myIntent);
                            dialog.cancel();
                        }
                    })
            .setNegativeButton("Cancel",
                    new DialogInterface.OnClickListener() {
                        public void onClick(DialogInterface dialog, int id) {
                            // cancel the dialog box
                            dialog.cancel();
                        }
                    });
    AlertDialog alert = builder.create();
    alert.show();
}
@Override
public void onLocationChanged(Location location) {
    double lng=location.getLongitude();
    double lat=location.getLatitude();
    fromPosition = new LatLng(lat,lng);
}

@Override
public void onStatusChanged(String provider, int status, Bundle extras) {

}

@Override
public void onProviderEnabled(String provider) {

}

@Override
public void onProviderDisabled(String provider) {

}

public void DrawRoute(){
    mMap.animateCamera(CameraUpdateFactory.newLatLngZoom(fromPosition, 16));
    mMap.addMarker(new MarkerOptions().position(fromPosition).title("Start"));
    mMap.addMarker(new MarkerOptions().position(toPosition).title("End"));
    Document doc = md.getDocument(fromPosition, toPosition, GMapV2Direction.MODE_DRIVING);
   /* int duration = md.getDurationValue(doc);
    String distance = md.getDistanceText(doc);
    String start_address = md.getStartAddress(doc);
    String copy_right = md.getCopyRights(doc);*/

    ArrayList<LatLng> directionPoint = md.getDirection(doc);
    PolylineOptions rectLine = new PolylineOptions().width(3).color(Color.RED);

    for(int i = 0 ; i < directionPoint.size() ; i++) {
        rectLine.add(directionPoint.get(i));
    }
    mMap.addPolyline(rectLine);
}

@Override
protected void onResume() {
    super.onResume();
    service.requestLocationUpdates(provider, 5000, 10, this);
}

}

But when I check location I found it alwaus = null can anyone help me to get my location

Answer 1

Make a simple single location update like this

   locationManager.requestSingleUpdate(provider,locationListener,null);

Official Doc: LocationManager check more similar methods And

Enable this settings Settings -> Location and security -> Use Wireless network (Location determined by wifi and/or mobile network)