Android按2次返回键退出程序

 1 @Override
 2 public boolean onKeyDown(int keyCode, KeyEvent event) {
 3 long exitTime = 0;
 4 复制代码
 5 // 判断按下的是不是返回键
 6             if(keyCode == KeyEvent.KEYCODE_BACK && event.getAction() == KeyEvent.ACTION_DOWN){   
 7                 if((System.currentTimeMillis()-exitTime) > 2000){  
 8                     Toast.makeText(getApplicationContext(), "再按一次退出程序", Toast.LENGTH_SHORT).show();                                
 9                     exitTime = System.currentTimeMillis();   
10                 } else {
11                     finish();
12                     System.exit(0);
13                 }
14                 return true;   
15             }
16             return super.onKeyDown(keyCode, event);
17         }