1 @Override
 2     public boolean onKeyDown(int keyCode, KeyEvent event)
 3     {
 4         if(keyCode == KeyEvent.KEYCODE_BACK){
 5             quitApp();
 6             return false;
 7         }else{
 8             return super.onKeyDown(keyCode, event);
 9         }
10     }
11     /**
12      * 退出APP
13      */
14     private void quitApp(){
15         if(isExit){
16             Intent intent = new Intent(Intent.ACTION_MAIN);
17             intent.addCategory(Intent.CATEGORY_HOME);
18             startActivity(intent);
19             System.exit(0);
20         }else{
21             isExit = true;
22             Tools.showText(mContext, "再按一次退出应用");
23             mHandler.sendEmptyMessageDelayed(0, 2000);
24         }
25     }
26     Handler mHandler = new Handler(){
27         public void handleMessage(android.os.Message msg) {
28             super.handleMessage(msg);
29             isExit = false;
30         };
31     };

 1 @Override
 2     public boolean onKeyDown(int keyCode, KeyEvent event)
 3     {
 4         if(keyCode == KeyEvent.KEYCODE_BACK && event.getRepeatCount() == 0)
 5             quitApp();
 6         return false;
 7     }
 8     private long exitTime = 0;
 9     private void quitApp(){
10         if(System.currentTimeMillis() - exitTime > 2000){
11             Tools.showText(mContext, "再按一次退出应用");
12             exitTime = System.currentTimeMillis();
13         }else{
14             finish();
15         }
16     }