Android中再按一次退出提醒实现的两种方法

 long waitTime = 2000;  long touchTime = 0;  @Override public boolean onKeyDown(int keyCode, KeyEvent event) { if(event.getAction() == KeyEvent.ACTION_DOWN && KeyEvent.KEYCODE_BACK == keyCode) {      long currentTime = System.currentTimeMillis();      if((currentTime-touchTime)>=waitTime) {      //让Toast的显示时间和等待时间相同       Toast.makeText(this, "再按一次退出", (int)waitTime).show();        touchTime = currentTime;      }else {        finish();      }      return true;    }    return super.onKeyDown(keyCode, event);  }

 @Override public void onBackPressed() {    long currentTime = System.currentTimeMillis();     if((currentTime-touchTime)>=waitTime) {      //让Toast的显示时间和等待时间相同      Toast.makeText(this, "再按一次退出", (int)waitTime).show();       touchTime = currentTime;     }else {       finish();     }  }