Get GPS Location instantly via Android app

Questions

all. I am writing an android app about GPS locations.

I tried it on emulator and entered the latitude and longitude manually, and it worked fine. However, my problem is: on the real device, in debugging mode, to go the next class by using intent can only be achieved when location is changed. If I start the app directly, I can see the blinking GPS icon, but the app will only stay here, and won t start the next activity. It seems that the variables in the onLocationChanged() will never be changed.

I have heard that to get the location instantly is to use the getLastKnownLocation() method. But I failed to get where I should use it.

Here is the class of how I use the LocationManager to get the locations.

Is there any solutions? I am quite confused. Thank you very much!!

    public class mainMenu extends Activity{

private LocationManager locationManager = null;

public void onCreate(Bundle savedInstanceState){
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);




    Button button1 = (Button)findViewById(R.id.button1);
    button1.setOnClickListener(new OnClickListener(){
        public void onClick(View v){

            Intent i3 = new Intent();
            i3.setClass(mainMenu.this, police.class);
            i3.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
            mainMenu.this.startActivityForResult(i3,0);


        }
    });

    Button button2 = (Button)findViewById(R.id.button2);
    button2.setOnClickListener(new OnClickListener(){
        public void onClick(View v){

            Intent i3 = new Intent();
            i3.setClass(mainMenu.this, ambulance.class);
            i3.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
            mainMenu.this.startActivityForResult(i3,0);


        }
    });

    Button button3 = (Button)findViewById(R.id.button3);
    button3.setOnClickListener(new OnClickListener(){
        public void onClick(View v){

            Intent i3 = new Intent();
            i3.setClass(mainMenu.this, fire_station.class);
            i3.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
            mainMenu.this.startActivityForResult(i3,0);


        }
    });



        locationManager = (LocationManager)mainMenu.this.getSystemService(Context.LOCATION_SERVICE);

        locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 120000 , 0, new MyLocationUpdater());

        String provider = LocationManager.GPS_PROVIDER;
        Location location = locationManager.getLastKnownLocation(provider);



}



public class MyLocationUpdater implements LocationListener{ //change location interface
    @Override
    public void onLocationChanged(Location location) {
        // TODO Auto-generated method stub
    //          store the location data
    //          get the best record



        Double lat = location.getLatitude();
        Double lon = location.getLongitude();

        System.out.println("The latitude is " + lat + "and " 
                + "the longitude is "+ lon);


        Double lat11 = lat - 1/69.0;
        Double lat12 = lat + 1/69.0;
        Double lon11 = lon - 1/42.0;
        Double lon12 = lon + 1/42.0;

        StaticVariables.latS1 = lat11.toString();
        StaticVariables.latN1 = lat12.toString();
        StaticVariables.lonW1 = lon11.toString();
        StaticVariables.lonE1 = lon12.toString();

        Double lat111 = lat - 2/69.0;
        Double lat121 = lat + 2/69.0;
        Double lon111 = lon - 2/42.0;
        Double lon121 = lon + 2/42.0;

        StaticVariables.latS11 = lat111.toString();
        StaticVariables.latN11 = lat121.toString();
        StaticVariables.lonW11 = lon111.toString();
        StaticVariables.lonE11 = lon121.toString();

    //          ==================================================
    //          ambulances

        Double lat21 = lat - 3/69.0;
        Double lat22 = lat + 3/69.0;
        Double lon21 = lon - 3/42.0;
        Double lon22 = lon + 3/42.0;

        StaticVariables.latS2 = lat21.toString();
        StaticVariables.latN2 = lat22.toString();
        StaticVariables.lonW2 = lon21.toString();
        StaticVariables.lonE2 = lon22.toString();

        Double lat211 = lat - 5.5/69.0;
        Double lat221 = lat + 5.5/69.0;
        Double lon211 = lon - 5.5/42.0;
        Double lon221 = lon + 5.5/42.0;

        StaticVariables.latS21 = lat211.toString();
        StaticVariables.latN21 = lat221.toString();
        StaticVariables.lonW21 = lon211.toString();
        StaticVariables.lonE21 = lon221.toString();

    //          ===================================================
    //          fire stations

        Double lat31 = lat - 2/69.0;
        Double lat32 = lat + 2/69.0;
        Double lon31 = lon - 2/42.0;
        Double lon32 = lon + 2/42.0;

        StaticVariables.latS3 = lat31.toString();
        StaticVariables.latN3 = lat32.toString();
        StaticVariables.lonW3 = lon31.toString();
        StaticVariables.lonE3 = lon32.toString();

        Double lat311 = lat - 2/69.0;
        Double lat321 = lat + 2/69.0;
        Double lon311 = lon - 2/42.0;
        Double lon321 = lon + 2/42.0;

        StaticVariables.latS31 = lat311.toString();
        StaticVariables.latN31 = lat321.toString();
        StaticVariables.lonW31 = lon311.toString();
        StaticVariables.lonE31 = lon321.toString();

        Intent intent = new Intent();
        intent.setClass(mainMenu.this, getPhoneNumber.class);
        mainMenu.this.startActivity(intent);
    }

    @Override
    public void onProviderDisabled(String arg0) {
        // TODO Auto-generated method stub

    }

    @Override
    public void onProviderEnabled(String arg0) {
        // TODO Auto-generated method stub

    }

    @Override
    public void onStatusChanged(String arg0, int arg1, Bundle arg2) {
        // TODO Auto-generated method stub

    }
}

    }

Answers

The getLastKnownLocation method does not trigger an onLocationChanged event. One way to refactor your code would be to move the logic that acts on a Location to a separate method and then call that method both after you call getLastKnownLocation, and from your onLocationChanged method.

Bear in mind that there is no guarantee that getLastKnownLocation will provide a meaningful Location, since you the device might have moved since the last location update.

Example code:

public void onCreate(Bundle savedInstanceState){
    ....
    String provider = LocationManager.GPS_PROVIDER;
    Location location = locationManager.getLastKnownLocation(provider);
    updateLocation(location);
}

public class MyLocationUpdater implements LocationListener{ //change location interface
    @Override
    public void onLocationChanged(Location location) {
        updateLocation(location);
    }
    ...
}

void updateLocation(Location location) {
    Double lat = location.getLatitude();
    Double lon = location.getLongitude();

    // the rest of the code from onLocationChanged
}

Source

License : cc by-sa 3.0

http://stackoverflow.com/questions/6068614/get-gps-location-instantly-via-android-app

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