Unity的web图片管理，自动回收

ImageManager.cs

//#define _Debug_Tools
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using System.IO;

public class ImageManager : MonoBehaviour
{
	public static void Request(string url, System.Action<Texture2D> callback)
	{
		Ins.StartCoroutine(Request_impl(url, callback));
	}
	public static void Release(Texture tex)
	{
		_TexInfo texInfo = null;
		if (m_dict.TryGetValue(tex.name, out texInfo))
		{
			texInfo.Release();
			Debug.LogFormat("Release [{0}]", tex.name);
		}
		else
		{
			Destroy(tex);
			Debug.LogWarningFormat("Can not find [{0}] in image manager, destroy it now", tex.name);
		}
		collectTime = 10;
	}
	private static readonly string ImagePath = "{0}/Image/{1}{2}";
	private static IEnumerator Request_impl(string url, System.Action<Texture2D> action)
	{
		_TexInfo texInfo = null;
		if (m_dict.TryGetValue(url, out texInfo))
		{
			Debug.LogFormat("[{0}] already managed", url);
			action(texInfo.Get());
		}
		else
		{
			var ext = Path.GetExtension(url);
			string fileName = HashTools.GenMD5String(url);
			string path = string.Format(ImagePath, Application.persistentDataPath, fileName, ext);
			if (File.Exists(path))
			{
				Debug.LogFormat("Exist {0}", path);
				WWW request = new WWW("file://" + path);
				yield return request;
				texInfo = new _TexInfo(request.texture, url);
				m_dict.Add(url, texInfo);
				action(texInfo.Get());
			}
			else
			{
				Debug.LogFormat("Not exist {0}", url);
				WWW request = new WWW(url);
				yield return request;
				if (!string.IsNullOrEmpty(request.error))
				{
					action(null);
					yield break;
				}
				Directory.CreateDirectory(Application.persistentDataPath + "/Image");
				File.WriteAllBytes(path, request.bytes);
				texInfo = new _TexInfo(request.texture, url);
				m_dict.Add(url, texInfo);
				action(texInfo.Get());
			}
		}
	}
	private class _TexInfo
	{
		private Texture2D texture;
		public int usingCount { get; private set; }
		public int usedCount { get; private set; }

		public _TexInfo(Texture2D tex, string url)
		{
			texture = tex;
			texture.name = url;
		}

		public Texture2D Get()
		{
			++usingCount;
			++usedCount;
			return texture;
		}
		public void Release()
		{
			--usingCount;
		}
	}
	private static Dictionary<string, _TexInfo> m_dict = new Dictionary<string, _TexInfo>();
	private static ImageManager _ins;
	private static ImageManager Ins
	{
		get
		{
			if (null == _ins)
			{
				GameObject mgr = new GameObject("_ImageManager");
				_ins = mgr.AddComponent<ImageManager>();
			}
			return _ins;
		}
		set
		{
			_ins = value;
		}
	}
#if _Debug_Tools
#if UNITY_EDITOR
	public int nextCollect = 0;
	private IEnumerator TimeCollect()
	{
		nextCollect = collectTime;
		int count = collectTime;
		int pre = nextCollect;
		for (int index = 0; index < count; ++index)
		{
			if (pre != nextCollect)
			{
				break;
			}
			nextCollect--;
			pre = nextCollect;
			yield return new WaitForSeconds(1.0f);
		}
	}
#endif
#endif
	private static int collectTime = 10;
	void Start()
	{
		StartCoroutine(Collect());
	}
	private static IEnumerator Collect()
	{
		for (bool removed = false; ;)
		{
			foreach (var pair in m_dict)
			{
				if (pair.Value.usingCount == 0)
				{
					m_dict.Remove(pair.Key);
					removed = true;
					Destroy(pair.Value.Get());
					Debug.LogFormat("Destroy {0}", pair.Key);
					break;
				}
			}
			if (removed)
			{
				removed = false;
				collectTime = 0;
				yield return new WaitForEndOfFrame();
			}
			else
			{
#if _Debug_Tools
#if UNITY_EDITOR
				collectTime = 10;
				Ins.StartCoroutine(Ins.TimeCollect());
#endif
#else
				collectTime = Mathf.Clamp(collectTime + 1, 10, 30);
#endif
				yield return new WaitForSeconds(collectTime);
			}
		}
	}
	public static void ForceCollect()
	{
		Ins.StartCoroutine(ForceCollect_impl());
	}
	private static IEnumerator ForceCollect_impl()
	{
		Debug.Log("Force collect textures memory");
		for (bool removed = false; !removed;)
		{
			foreach (var pair in m_dict)
			{
				if (pair.Value.usingCount == 0)
				{
					m_dict.Remove(pair.Key);
					removed = true;
					Destroy(pair.Value.Get());
					Debug.LogFormat("Destroy {0}", pair.Key);
					break;
				}
			}
			yield return new WaitForEndOfFrame();
		}
	}
}