Question

当用户输入的当前处理完成时，有没有办法安排方法调用？某些喜欢将用户消息发布到消息队列。

让我们来看看如何处理用户输入：

1. User taps the screen                                      |  User input
2. Operating system puts a message in message queue          |  Operating system
3. WPF internals pick up the message                         \
4. WPF internals processes the message                        | WPF internals
5. WPF causes parts of application code to be run:           /
    a) As immediate reactions on events                      \  This is where call may
    b) As an effect of dependency properties being changed   /  be scheduled
6. The application code finishes                             |  Application code
7. The WPF internals finishes their work                     |  WPF internals
   *** This is where I want the scheduled method to run ***
8. WPF peeks for next message from message queue             |  WPF internals

我如何安排通话，以便在我想要的地方进行通话？

Answer 1

如果我理解你的问题，那么我就是这样解决的。

声明2个全局变量：

Action<object> gPostProcessingMethod = null;//it must be accessible to any of the methods
                       // that may decide to schedule post-processing of your message
object gDataForPostProcessing = null;//it will hold a data for post-processing (if any)

我假设你有一个循环在某个地方轮询你的消息队列。我们假设这是while循环。然后它应该看起来像这样来处理你的消息的后处理：

    while (...)
    {
        // 1. Your code to dequeue/get next message:
        // .................................
        gPostProcessingMethod= null;
        gDataForPostProcessing = null;
        /* 2. Your code that triggers processing of the message. As far as I understand,
              this triggering method does not return until all of the subsequently called
              methods are done.
              However, as you described, any of those methods may decide to schedule 
              "post-processing" method that must start at the moment the processing is complete.
              This is how the scheduling should be done: 
                  gPostProcessingMethod = <AnyMethodThatCompliesWithSignatureOfAction>  
                  gDataForPostProcessing = ...;
        */


        if (gPostProcessingMethod != null)
        {//You mentioned that this call MUST happen synchronously (otherwise you may use ThreadPool, etc.)
             gPostProcessingMethod(gDataForPostProcessing);
        }
        // 3. Your remaining code in the loop:
        // ......................................

    }

由于每个后续处理方法都可以覆盖先前分配给gPostProcessingMethod和gDataForPostProcessing的值，因此您应该接受下游方法具有优先级或相反：禁止更改这些变量（如果有）已经确定。

Answer 2

有很多方法可以完成这项工作。我个人倾向于实施此类行为是使用ConcurrentQueue<>

Answer 3

您可以使用信号量进行多线程处理，或者当单线程只是一个在方法开始时增加的int并在方法结束时减少。你只需等到它回到零。

如何在C＃中延迟方法调用？

3 个答案: