在一个协同程序中，我正在使用OkHttpClient执行一个http请求.请求是从一个包含suspend关键字的函数完成的:
suspend fun doSomethingFromHttp(someParam:String): Something {
...
val response = HttpReader.get(url)
return unmarshalSomething(response)!!
}
我假设函数可以在进入时挂起，因为它有关键字suspend，但是协程在执行http请求时也会挂起吗？其他类型的阻塞IO怎么办？
There's no automagic going on with Kotlin coroutines. If you call a blocking function like HttpReader.get(), the coroutine won't be suspended and instead the call will block. You can easily assure yourself that a given function won't cause the coroutine to suspend: if it's not a suspend function, it cannot possibly do it, whether or not it's called from a suspend function.
如果要将现有的阻塞API转换为非阻塞、可挂起的调用，必须将阻塞调用提交给线程池.实现这一目标的最简单方法如下:
val response = withContext(Dispatchers.IO) { HttpReader.get(url) }
withContext is a suspend fun that will suspend the coroutine, submit the provided block to another coroutine dispatcher (here IO) and resume when that block is done and has come up with its result.
您还可以轻松实例化自己的ExecutorService，并将其用作协同程序调度器:
val myPool = Executors.newCachedThreadPool().asCoroutineDispatcher()
现在你可以写作了
val response = withContext(myPool) { HttpReader.get(url) }
This way you work against a thread pool that is under your control, as opposed to the global IO. Just keep in mind that you are now also responsible to close() it.