unity 中的协程

        //The coroutine will continue after all Update functionshave been calledon the next frame.

        yield return ;

        //Continue after a specified time delay, after all Update functions have been called for the frame.

        yield return new WaitForSeconds();

        // Continue after all FixedUpdate has been called on all scripts.

        yield return new WaitForFixedUpdate();

        // after a WWW download has completed

        yield return new WWW("url");

        //Chains the coroutine, and will wait for the MyFunc coroutine to complete first.

        yield return StartCoroutine(LoadPic(urls));