Android “再按一次退出“

 1 @Override
 2     public boolean onKeyDown(int keyCode, KeyEvent event) {
 3         if (keyCode == KeyEvent.KEYCODE_BACK) 
 4         {
 5             if ((System.currentTimeMillis() - mExitTime) > 2000) { //第一种：判断2次按后退键间隔是否在2秒内
 6             /*if(event.getRepeatCount() == 0) //第二种，判断是否重复按后退键
 7             {*/
 8                 System.out.println(mExitTime);
 9                 Object mHelperUtils;
10                 showTips(R.drawable.tips_smile, "再按一次返回桌面");
11                 mExitTime = System.currentTimeMillis();
12 
13             } else {
14                 finish();
15             }
16             return true; 
17         }
18         return super.onKeyDown(keyCode, event);
19     }