Unity 加载网络图片

来源：互联网发布：哆啦A梦知乎编辑：程序博客网时间：2024/05/18 18:45

IOS工程师都应该用过SDWebImage或者android工程师应该使用过Glide，fresco，Imageloader等，在Unity里面，我按照同样的原理封装了一个ImageLoader 。

原理就是先用一张placeholder来显示图片，等待图片加载，等加载完了之后替换placeholder，第二次加载网络图片时，先判断本地时候已经加载过图片，如果加载过就从本地获取图片，如果没有就去网络上加载。

下面代码：

using UnityEngine;using UnityEngine.UI;using System.Collections;using System.IO;public class AsyncImageDownload : MonoBehaviour{    public Sprite placeholder;    private static AsyncImageDownload _instance = null;    public static AsyncImageDownload GetInstance() { return Instance; }    public static AsyncImageDownload Instance    {        get        {            if(_instance==null)            {                GameObject obj = new GameObject("AsyncImageDownload");                _instance = obj.AddComponent<AsyncImageDownload>();                DontDestroyOnLoad(obj);                _instance.Init();            }            return _instance;        }    }    public bool Init()    {        if (!Directory.Exists(Application.persistentDataPath + "/ImageCache/"))        {            Directory.CreateDirectory(Application.persistentDataPath + "/ImageCache/");        }        if(placeholder==null)        {            placeholder = Resources.Load("placeholder") as Sprite;        }        return true;    }    public void SetAsyncImage(string url, Image image)    {        //开始下载图片前，将UITexture的主图片设置为占位图        image.sprite = placeholder;        //判断是否是第一次加载这张图片        if (!File.Exists(path + url.GetHashCode()))        {            //如果之前不存在缓存文件            StartCoroutine(DownloadImage(url, image));        }        else {            StartCoroutine(LoadLocalImage(url, image));        }    }    IEnumerator DownloadImage(string url, Image image)    {        Debug.Log("downloading new image:" + path + url.GetHashCode());//url转换HD5作为名字        WWW www = new WWW(url);        yield return www;        Texture2D tex2d = www.texture;        //将图片保存至缓存路径        byte[] pngData = tex2d.EncodeToPNG();        File.WriteAllBytes(path + url.GetHashCode(), pngData);        Sprite m_sprite = Sprite.Create(tex2d, new Rect(0, 0, tex2d.width, tex2d.height), new Vector2(0, 0));        image.sprite = m_sprite;    }    IEnumerator LoadLocalImage(string url, Image image)    {        string filePath = "file:///" + path + url.GetHashCode();        Debug.Log("getting local image:" + filePath);        WWW www = new WWW(filePath);        yield return www;        Texture2D texture = www.texture;        Sprite m_sprite = Sprite.Create(texture,new Rect(0, 0, texture.width, texture.height), new Vector2(0, 0));        image.sprite = m_sprite;    }    public string path    {        get        {            //pc,ios //android :jar:file//            return Application.persistentDataPath + "/ImageCache/";                    }    }}

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