Check GPS activation on Android and prompt user to change GPS setting

.java

final LocationManager manager = (LocationManager) getSystemService( Context.LOCATION_SERVICE );

    if ( !manager.isProviderEnabled( LocationManager.GPS_PROVIDER ) ) {
        buildAlertMessageNoGps();
    }

  private void buildAlertMessageNoGps() {
    final AlertDialog.Builder builder = new AlertDialog.Builder(this);
    builder.setMessage("Your GPS seems to be disabled, do you want to enable it?")
           .setCancelable(false)
           .setPositiveButton("Yes", new DialogInterface.OnClickListener() {
               public void onClick(@SuppressWarnings("unused") final DialogInterface dialog, @SuppressWarnings("unused") final int id) {
                   startActivity(new Intent(android.provider.Settings.ACTION_LOCATION_SOURCE_SETTINGS));
               }
           })
           .setNegativeButton("No", new DialogInterface.OnClickListener() {
               public void onClick(final DialogInterface dialog, @SuppressWarnings("unused") final int id) {
                    dialog.cancel();
               }
           });
    final AlertDialog alert = builder.create();
    alert.show();
}

// 	I would advise declaring alert for the whole activity so you can dismiss it here in onDestroy to avoid a memory leak 
@Override
    protected void onDestroy() {
        super.onDestroy();
        if(alert != null) { alert.dismiss(); }
    }