P16 Cancel Task 取消活动

Pattern 16 Cancel Task 取消活动 An enabled task is withdrawn prior to it commencing execution. If the task has started, it is disabled and, where possible, the currently running instance is halted and removed. 一个可执行的活动被强制失效了，也就是说，一个正在等待执行的活动所在线程被移除了。