当点击Form上的X或用ESC关闭Form时系统会掉用canClose()和close()方法。canClose()方法会有个boolean的ret来决定是否关闭Form，close()方法当用户点击x时会得不到数据。当Form上有OKbutton时点击Ok会调用okclose()canclose()close()当Form上有CANCELbutton时点击Cancel会调用cancelclose()canclose()close()form上还有几个closed(),closedOK(),closedCancel()方法来判断form被关闭时的状态如是被OKbutton关闭的还是被Cancelbutton关闭的或是点击X或esc关闭的当被OKbutton关闭会掉用okclose()canclose()close()closedOK()closed()当被Cancelbutton关闭时会调用cancelclose()canclose()close()closedCancel()closed()其他情况下是canclose()close()closed()
