再按一次退出程序

Android 1.0 到 Android 2.1 SDK

private long exitTime = 0; 

 1 @Override
 2     public boolean onKeyDown(int keyCode, KeyEvent event) {
 3         // TODO Auto-generated method stub
 4         
 5         if(keyCode == KeyEvent.KEYCODE_BACK && event.getAction() == KeyEvent.ACTION_DOWN){
 6             if(System.currentTimeMillis() - exitTime > 2000){
 7                 Toast.makeText(this, "再按一次退出程序", Toast.LENGTH_SHORT).show();
 8                 exitTime = System.currentTimeMillis();
 9             }else{
10                 finish();
11                 System.exit(0);
12             }
13         }
14             
15         return super.onKeyDown(keyCode, event);
16     }

Android 2.0 以上 SDK

 1 @Override
 2     public void onBackPressed() {
 3         // TODO Auto-generated method stub
 4         //super.onBackPressed();
 5         if(System.currentTimeMillis() - exitTime > 2000){
 6             Toast.makeText(this, "再按一次退出程序", Toast.LENGTH_SHORT).show();
 7             exitTime = System.currentTimeMillis();
 8         }else{
 9             finish();
10             System.exit(0);
11         }
12     }