原文网址：http://blog.csdn.net/jumping_android/article/details/7571309

1. @Override  
2.     public boolean onKeyDown(int keyCode, KeyEvent event) {  
3.         if (keyCode == KeyEvent.KEYCODE_BACK && event.getRepeatCount() == 0) {  
4.             dialog();  
5.             return true;  
6.         }  
7.         return true;  
8.     }  

1. protected void dialog() {  
2.         AlertDialog.Builder builder = new Builder(AccoutList.this);  
3.         builder.setMessage("确定要退出吗?");  
4.         builder.setTitle("提示");  
5.         builder.setPositiveButton("确认",  
6.         new android.content.DialogInterface.OnClickListener() {  
7.             @Override  
8.             public void onClick(DialogInterface dialog, int which) {  
9.                 dialog.dismiss();  
10.                 //AccoutList.this.finish();  
11.                 //System.exit(1);  
12.                 android.os.Process.killProcess(android.os.Process.myPid());  
13.             }  
14.         });  
15.         builder.setNegativeButton("取消",  
16.         new android.content.DialogInterface.OnClickListener() {  
17.             @Override  
18.             public void onClick(DialogInterface dialog, int which) {  
19.                 dialog.dismiss();  
20.             }  
21.         });  
22.         builder.create().show();  
23.     }