在实现一个页面或在实现一个类的方法时，因为页面是复杂的，类是复杂的，所以常常不是“一步到位”的实现，而是逐步渐进式、小步往前推进式的，即先实现所要求的功能的一小部份，运行，调试，修改错误，正确之后，再实现另一小部份功能，运行，调试，修改错误，如此循环，直至最终实现了该页面或该类的功能。-In the realization of a page or in the realization of a class method, because the page is complex, class is complex, it is often not a " one-step"　to achieve, but gradually progressive, forward-propelled small step, that is, first achieve the required functionality for a small part of the run, debug, modify the error, correct, and then realize another small part of functionality, run, debug, modify the error, and so on, until the final realization of the pages or the class function.