说明：  这个例子中，我们假设应用程序窗体是一个一直显示当前时间的数字时钟，当你使其执行“大任务”直到任务的完成，这期间你会发现数字时钟窗体从来就没有被“挂起”过，仍然能够响应你的拖动操作和不停地显示时间。
(This example, we assume that the application form has been a digital clock displays the current time, when you make the implementation of the " big task" until the completion of the task, during which you will find digital clock form never been " suspended " However, you are still able to respond to constantly drag and display time.)