Android开发---按两次Back键退出

  思路1：记录上次点击的时间，与本次点击的时间比较，当两次时间间隔小于一定值时，退出，否则提示“再按一次退出程序”，同时更新上次点击时间

    

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1. private long firstTime = 0;  
2.    @Override  
3. public boolean onKeyUp(int keyCode, KeyEvent event) {  
4.        // TODO Auto-generated method stub  
5.        switch(keyCode)  
6.        {  
7.        case KeyEvent.KEYCODE_BACK:  
8.             long secondTime = System.currentTimeMillis();   
9.              if (secondTime - firstTime > 2000) {                                         //如果两次按键时间间隔大于2秒，则不退出  
10.                  Toast.makeText(this, "再按一次退出程序", Toast.LENGTH_SHORT).show();   
11.                  firstTime = secondTime;//更新firstTime  
12.                  return true;   
13.              } else {                                                    //两次按键小于2秒时，退出应用  
14.             System.exit(0);  
15.              }   
16.            break;  
17.        }  
18.      return super.onKeyUp(keyCode, event);  
19.    }  

     思路2：开线程延时处理

[java]  view plain  copy

1. private int mBackKeyPressedTimes = 0;  
2.   
3.         @Override  
4.         public void onBackPressed() {  
5.                 if (mBackKeyPressedTimes == 0) {  
6.                         Toast.makeText(this, "再按一次退出程序 ", Toast.LENGTH_SHORT).show();  
7.                         mBackKeyPressedTimes = 1;  
8.                         new Thread() {  
9.                                 @Override  
10.                                 public void run() {  
11.                                         try {  
12.                                                 Thread.sleep(2000);  
13.                                         } catch (InterruptedException e) {  
14.                                                 e.printStackTrace();  
15.                                         } finally {  
16.                                                 mBackKeyPressedTimes = 0;  
17.                                         }  
18.                                 }  
19.                         }.start();  
20.                         return;  
21.                       else{  
22.                                this.activity.finish();  
23.                             }  
24.                 }  
25.                 super.onBackPressed();  
26.         }