Unity 之 C# 利用回调函数实现C++匿名函数

using UnityEngine;
using System.Collections;

public class AClass{

	public delegate void onComplete(Sprite sprite);

	public IEnumerator GetTexture(onComplete callback)
	{
		//save
		Texture2D t=new Texture2D(Screen.width,(int)(Screen.width*aspect));
		t.ReadPixels(new Rect(0,0,Screen.width,(int)(Screen.width*aspect)),0,0,false);
		t.Apply();
		byte[] byt = t.EncodeToPNG();
		m_photoName = Time.time+".png";
		m_photoPath = Globe.persistentDataUrl+m_photoName;

		Debug.Log("System.IO++++++++Start WritePng");
		System.IO.File.WriteAllBytes(m_photoPath.Replace("file://",""),byt);
		
		Debug.Log("m_photoPath="+m_photoPath);
		//load image
		WWW www = new WWW(m_photoPath);
		yield return www;

		//回调
		callback(sprite);
	}
}

using UnityEngine;
using System.Collections;

public class BClass{

	public void ExecuteCallBack(){

		StartCoroutine(m_webCamera.GetTexture(delegate(Sprite sp)
		{
			watermark.gameObject.SetActive(false);
			photoImg.sprite=sp;
		}));
	}
}

A类中定义了一个用于回调的Delegate，參数是要传递的精灵类。GetTexture方法是用于截屏的方法。

B类中是调用方式，当B类调用A类的截屏方法时，能够直接通过Delegate(Sprite sp) 匿名函数来获取到sp得图片。应为A类中截屏方法中。使用了WWW的异步载入，所以B类中的给PhotoImg的精灵赋值也是异步的。

using UnityEngine;
using System.Collections;

public class BClass{

	public void ExecuteCallBack(){

		//StartCoroutine();
		m_webCamera.GetTexture(delegate(Sprite sp)
		{
			watermark.gameObject.SetActive(false);
			photoImg.sprite=sp;
		});
	}
}

可是。普通情况下使用匿名函数，多数人会想使用异步，这个时候StartCoroutine() 必须在调用的使用，即在B类中调用。假设在B类中不使用StartCortine() 而在A类中使用
即，在B类中调用A类的截屏方法

	public void ExecuteCallBack(){

		//StartCoroutine();
		
		m_webCamera.GetTexture(delegate(Sprite sp);

		m_webCamera.GetTexture(delegate(Sprite sp)
		{
			watermark.gameObject.SetActive(false);
			photoImg.sprite=sp;
		});
	}

而在A类的截屏其中使用StartCoroutine() 方法启用异步，则会出现空指针异常。这是我在使用过程中碰到的问题。困扰了我有一会儿呢，希望大家注意！！

！

using UnityEngine;
using System.Collections;

public class AClass{

	public delegate void onComplete(Sprite sprite);

	public void GetTexture(onComplete callback){
	
		StartCoroutine(ScreenCapture(callback));
	}

	public IEnumerator ScreenCapture(onComplete callback)
	{
		//save
		Texture2D t=new Texture2D(Screen.width,(int)(Screen.width*aspect));
		t.ReadPixels(new Rect(0,0,Screen.width,(int)(Screen.width*aspect)),0,0,false);
		t.Apply();
		byte[] byt = t.EncodeToPNG();
		m_photoName = Time.time+".png";
		m_photoPath = Globe.persistentDataUrl+m_photoName;

		Debug.Log("System.IO++++++++Start WritePng");
		System.IO.File.WriteAllBytes(m_photoPath.Replace("file://",""),byt);
		
		Debug.Log("m_photoPath="+m_photoPath);
		//load image
		WWW www = new WWW(m_photoPath);
		yield return www;

		//回调

		callback(sprite);
	}
}