不管 InvokeRequired 调用 Invoke 有什么问题? [英] What's wrong with calling Invoke, regardless of InvokeRequired?

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问题描述

我已经看到了对 GUI 控件进行跨线程访问的常见设置,如下所述:最短的写法对 Windows 窗体控件的线程安全访问方法

I've seen the common setup for cross threading access to a GUI control, such as discussed here: Shortest way to write a thread-safe access method to a windows forms control

我发现的所有网络点击都描述了类似的事情.

All the web hits I found describe a similar thing.

但是,为什么我们需要检查 InvokeRequired?我们不能直接调用 Invoke 吗?

However, why do we need to check InvokeRequired? Can't we just call Invoke directly?

我假设答案是否定的,所以我真正的问题是为什么"?

I assume the answer is no, so my real question is 'why'?

推荐答案

从非 UI 线程我们无法触摸 UI - 可能会发生非常糟糕的事情,因为控件具有线程关联性.因此,我们必须(至少)从非 UI 线程调用 InvokeBeginInvoke.

From non-UI threads we can't touch the UI - very bad things can happen, since controls have thread affinity. So from a non-UI thread we must (at a minumum) call Invoke or BeginInvoke.

然而,对于 UI 线程 - 我们想要调用 Invoke 很多时间;问题是,如果您已经在 UI 线程上,它仍然有向表单的泵发送消息并进行处理的不必要开销.

For UI-threads, however - we don't want to call Invoke lots of time; the issue is that if you are already on the UI thread, it still has the unnecessary overhead of sending a message to the form's pump and processing it.

实际上,在您知道的大多数线程代码中,您希望在 -UI 线程上调用特定方法,因此在这些情况下,不需要额外的开销:只需调用 Invoke.

In reality, in most threading code you know you expect a specific method to be called on a non-UI thread, so in those cases, there is no additional overhead: just call Invoke.

这篇关于不管 InvokeRequired 调用 Invoke 有什么问题?的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持IT屋!

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