C# 忙等待

发布于 2024-11-04 02:23:35 字数 285 浏览 2 评论 0原文

如何以一种不完全低效的方式实现忙碌等待？我面临的问题是我只能以拉取方式加载模型的数据，这意味着我必须以连续的方式调用 getXYZ() 方法。

对于用户交互来说，这必须发生得不够快，但要足够快，以便当 GUI 中的状态发生更改时，模型可以被注意到，并且 getXYZ() 方法会接收到新状态。

我的方法很简单：

while (c.hasChanged()) {
   Thread.sleep(500);
}
updateData();

是否有更好的机制？

原文

How do you implement busy waiting in a not total inefficient way? I am facing the issue that I can load the data of my model only in a pull manner, which means I have to invoke getXYZ() methods in a continuous way.

This has to happen not fast enough for user interaction, but fast enought, that when a state in the GUI is changed, the model can be noticed and the new state is received by the getXYZ() methods.

My approach simply be:

while (c.hasChanged()) {
   Thread.sleep(500);
}
updateData();

Are there better mechanisms?

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紅太極 2024-11-11 02:23:35

您的问题似乎可以通过线程。

在 WPF 中，您可以执行以下操作：

Thread t = new Thread((ThreadStart)delegate() {
   while (true) {
      Thread.sleep(500);
      if (c.hasChanged())
          Dispatcher.Invoke((Action)delegate() {updateData();});
   }

}).Start();

在 WinForms 中，

Thread t = new Thread((ThreadStart)delegate() {
   while (true) {
      Thread.sleep(500);
      // this must derive from Control
      if (c.hasChanged())
          this.Invoke((Action)delegate() {updateData();});
   }

}).Start();

调用可能缺少参数（这是在调用 UI 线程上执行代码所必需的）但我是从我的大脑中编写此内容，因此没有可用的智能感知：D

在 .NET 4 中，您可以使用 TaskFactory.StartNew 而不是自己生成一个线程。
在 .Net <= 4 中，您可以使用 TreadPool 为线程。
但是我记得您需要立即运行它，因为您希望它尽快进行检查，并且线程池不会向您保证（它可能已经满了，但不太可能:-）。
只是不要做愚蠢的事情，比如循环生成更多它们！

在线程内部，您应该进行类似的检查

while (!Closing)

，以便线程可以在需要时完成，而不必求助于诸如 t.Abort(); 之类的坏东西
退出时将 Closing 设置为 true 并执行 t.Join() 来关闭检查器线程。

编辑：

我忘了说 Closing 应该是 bool 属性或 VOLATILE 布尔值，不是一个简单的布尔值，因为您无法确保线程能够完成（如果您正在关闭应用程序，那么它会完成，但最好让它们按您的意愿完成）。 volatile 关键字旨在防止（伪）编译器对假设变量值无法更改的代码应用任何优化

Your problem seems to be solvable with Threading.

In WPF you can do:

Thread t = new Thread((ThreadStart)delegate() {
   while (true) {
      Thread.sleep(500);
      if (c.hasChanged())
          Dispatcher.Invoke((Action)delegate() {updateData();});
   }

}).Start();

In WinForms

Thread t = new Thread((ThreadStart)delegate() {
   while (true) {
      Thread.sleep(500);
      // this must derive from Control
      if (c.hasChanged())
          this.Invoke((Action)delegate() {updateData();});
   }

}).Start();

There may be missing parameters to Invoke (which is needed to execute the code on the calling UI thread) but I'm writing this from my brain so no intellisense at disposal :D

In .NET 4 you can use TaskFactory.StartNew instead of spawning a thread by yourself.
In .Net <= 4, you could use the TreadPool for the thread.
However I recall you need this to be run at once because you expect it to be there checking as soon as possible and the thread pool won't assure you that (it could be already full, but not very likely:-).
Just don't do silly things like spawning more of them in a loop!

And inside the thread you should put a check like

while (!Closing)

so that the thread can finish when you need it without having to resort to bad things like t.Abort();
An when exiting put the Closing to true and do a t.Join() to close the checker thread.

EDIT:

I forgot to say that the Closing should be a bool property or a VOLATILE boolean, not a simple boolean, because you won't be ensured that the thread could ever finish (well it would in case you are closing the application, but it is good practice to make them finish by your will). the volatile keyword is intended to prevent the (pseudo)compiler from applying any optimizations on the code that assume values of variables cannot change

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