Android 软件退出系统方法重写

Android 软件退出系统按键方法重写
 1     //针对Andriod软件退出系统按键方法重写
 2 
 3     private long exitTime = 0;//key down time
 4     @Override
 5     public boolean onKeyDown(int keyCode, KeyEvent event) {
 6         switch (keyCode) {
 7             case KeyEvent.KEYCODE_BACK:
 8                 if (System.currentTimeMillis() - exitTime >= 2000) {
 9                     exitTime = System.currentTimeMillis();
10                     showToast(getString(R.string.quit_on_double_click_));
11                     return true;
12                 } else {
13                     showToast(getString(R.string.exiting));
14                     try {
15                         Thread.sleep(1000);
16                     } catch (InterruptedException e) {
17                         e.printStackTrace();
18                     }
19                     finish();
20                 }
21                 break;
22         }
23         return super.onKeyDown(keyCode, event);
24     }