Coroutine 切换调用的例子

原文地址 http://www.tuicool.com/articles/3IV32m
using System;
using System.Collections.Generic;
using System.Linq;
using UnityEngine;
using System.Collections;

[RequireComponent(typeof(GUIText))]
public class Hijack : MonoBehaviour {

//This will hold the counting up coroutine
IEnumerator countUp;
//This will hold the counting down coroutine
IEnumerator countDown;
//This is the coroutine we are currently
//hijacking
IEnumerator _current;

//A value that will be updated by the coroutine
//that is currently running
int value = 0;

void Start()
{

//Create our count up coroutine
_countUp = CountUp();
//Create our count down coroutine
_countDown = CountDown();
//Start our own coroutine for the hijack
StartCoroutine(DoHijack());

}

void Update()
{

//Show the current value on the screen
guiText.text = value.ToString();

}

void OnGUI()
{

//Switch between the different functions
if(GUILayout.Button("Switch functions"))
{
  if(_current == _countUp)
    _current = _countDown;
  else
    _current = _countUp;
}

}

IEnumerator DoHijack()
{

while(true)
{
  //Check if we have a current coroutine and MoveNext on it if we do
  if(_current != null && _current.MoveNext())
  {
    //Return whatever the coroutine yielded, so we will yield the
    //same thing
    yield return _current.Current;
  }
  else
    //Otherwise wait for the next frame
    yield return null;
}

}

IEnumerator CountUp()
{

//We have a local increment so the routines
//get independently faster depending on how
//long they have been active
float increment = 0;
while(true)
{
  //Exit if the Q button is pressed
  if(Input.GetKey(KeyCode.Q))
    break;
  increment+=Time.deltaTime;
  value += Mathf.RoundToInt(increment);
  yield return null;
}

}

IEnumerator CountDown()
{

float increment = 0f;
while(true)
{
  if(Input.GetKey(KeyCode.Q))
    break;
  increment+=Time.deltaTime;
  value -= Mathf.RoundToInt(increment);
  //This coroutine returns a yield instruction
  yield return new WaitForSeconds(0.1f);
}

}

}