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public class BackKeyTest extends Activity{	/** Called when the activity is first created. */	@Override	public void onCreate(Bundle savedInstanceState)	{		super.onCreate(savedInstanceState);		setContentView(R.layout.main);	}		@Override	public boolean onKeyDown(int keyCode, KeyEvent event)	{		if (keyCode == KeyEvent.KEYCODE_BACK )		{			// 创建退出对话框			AlertDialog isExit = new AlertDialog.Builder(this).create();			// 设置对话框标题			isExit.setTitle("系统提示");			// 设置对话框消息			isExit.setMessage("确定要退出吗");			// 添加选择按钮并注册监听			isExit.setButton("确定", listener);			isExit.setButton2("取消", listener);			// 显示对话框			isExit.show();		}				return false;			}	/**监听对话框里面的button点击事件*/	DialogInterface.OnClickListener listener = new DialogInterface.OnClickListener()	{		public void onClick(DialogInterface dialog, int which)		{			switch (which)			{			case AlertDialog.BUTTON_POSITIVE:// "确认"按钮退出程序				finish();				break;			case AlertDialog.BUTTON_NEGATIVE:// "取消"第二个按钮取消对话框				break;			default:				break;			}		}	};	}