GpsOn

private void Check(){
    	String provider = Settings.Secure.getString(getContentResolver(),
    	                                            Settings.Secure.LOCATION_PROVIDERS_ALLOWED);
        if(!provider.contains("gps")){ // if gps is disabled
        	new AlertDialog.Builder( this )
        		.setTitle( "Turn GPS" )
        		.setMessage( "The GPS is off you activate it ?" )
        		.setPositiveButton( "Yes", new DialogInterface.OnClickListener() {
        		public void onClick(DialogInterface dialog, int which) {
        	       	startActivity(new Intent(android.provider.Settings.ACTION_LOCATION_SOURCE_SETTINGS));
        		}})
        		.setNegativeButton( "No", new DialogInterface.OnClickListener() {
        		public void onClick(DialogInterface dialog, int which) {
        		}} )
        		.show(); 
        }
    }