How to implement Android press the quit program again

private boolean isExit;
    private Handler handler;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        (savedInstanceState);
        setContentView(.activity_main);
        handler = new Handler(){
            @Override
            public void handleMessage(Message msg) {
                (msg);
                isExit = false;
            }
        };
    }
public boolean onKeyDown(int keyCode, KeyEvent event) {
        if(keyCode==KeyEvent.KEYCODE_BACK){
            if(!isExit){
                isExit = true;
                (0, 1500);
(this, "Press again to launch the program", 1000).show();
                return false;
            }else{
                finish();
            }
        }
        return (keyCode, event);
    }