Android图片管理组件（双缓存+异步加载）

转自：http://www.oschina.net/code/snippet_219356_18887?p=3#comments

ImageManager2这个类具有异步从网络下载图片，从sd读取本地图片，内存缓存，硬盘缓存，图片使用动画渐现等功能，已经将其应用在包含大量图片的应用中一年多，没有出现oom

Android程序常常会内存溢出，网上也有很多解决方案，如软引用，手动调用recycle等等。但经过我们实践发现这些方案，都没能起到很好的效果，我们的应用依然会出现很多oom，尤其我们的应用包含大量的图片。android3.0之后软引用基本已经失效，因为虚拟机只要碰到软引用就回收，所以带不来任何性能的提升。

我这里的解决方案是HandlerThread(异步加载)+LruCache(内存缓存)+DiskLruCache(硬盘缓存)。

作为程序员，我也不多说，直接和大家共享我的代码，用代码交流更方便些。

源码demo地址：https://github.com/yueyueniao2012/multiimagechooser

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package com.example.util;   import java.io.File; import java.util.Iterator; import java.util.LinkedList; import java.util.Queue; import java.util.Stack;   import org.apache.http.HttpEntity; import org.apache.http.HttpResponse; import org.apache.http.client.methods.HttpGet; import org.apache.http.util.EntityUtils;   import android.app.ActivityManager; import android.content.Context; import android.graphics.Bitmap; import android.graphics.BitmapFactory; import android.graphics.drawable.BitmapDrawable; import android.graphics.drawable.ColorDrawable; import android.graphics.drawable.Drawable; import android.graphics.drawable.TransitionDrawable; import android.media.ThumbnailUtils; import android.os.Handler; import android.os.HandlerThread; import android.os.Looper; import android.os.Message; import android.support.v4.util.LruCache; import android.widget.ImageView;   import com.example.MyApplication;   /**  * 图片加载类  *  * @author 月月鸟  */ public class ImageManager2 {       private static ImageManager2 imageManager;     public LruCache<String, Bitmap> mMemoryCache;     private static final int DISK_CACHE_SIZE = 1024 * 1024 * 20; // 10MB     private static final String DISK_CACHE_SUBDIR = "thumbnails";     public DiskLruCache mDiskCache;     private static MyApplication myapp;       /** 图片加载队列，后进先出 */     private Stack<ImageRef> mImageQueue = new Stack<ImageRef>();       /** 图片请求队列，先进先出，用于存放已发送的请求。 */     private Queue<ImageRef> mRequestQueue = new LinkedList<ImageRef>();       /** 图片加载线程消息处理器 */     private Handler mImageLoaderHandler;       /** 图片加载线程是否就绪 */     private boolean mImageLoaderIdle = true;       /** 请求图片 */     private static final int MSG_REQUEST = 1;     /** 图片加载完成 */     private static final int MSG_REPLY = 2;     /** 中止图片加载线程 */     private static final int MSG_STOP = 3;     /** 如果图片是从网络加载，则应用渐显动画，如果从缓存读出则不应用动画 */     private boolean isFromNet = true;       /**      * 获取单例，只能在UI线程中使用。      *      * @param context      * @return      */     public static ImageManager2 from(Context context) {           // 如果不在ui线程中，则抛出异常         if (Looper.myLooper() != Looper.getMainLooper()) {             throw new RuntimeException("Cannot instantiate outside UI thread.");         }           if (myapp == null) {             myapp = (MyApplication) context.getApplicationContext();         }           if (imageManager == null) {             imageManager = new ImageManager2(myapp);         }           return imageManager;     }       /**      * 私有构造函数，保证单例模式      *      * @param context      */     private ImageManager2(Context context) {         int memClass = ((ActivityManager) context                 .getSystemService(Context.ACTIVITY_SERVICE)).getMemoryClass();         memClass = memClass > 32 ? 32 : memClass;         // 使用可用内存的1/8作为图片缓存         final int cacheSize = 1024 * 1024 * memClass / 8;           mMemoryCache = new LruCache<String, Bitmap>(cacheSize) {               protected int sizeOf(String key, Bitmap bitmap) {                 return bitmap.getRowBytes() * bitmap.getHeight();             }           };           File cacheDir = DiskLruCache                 .getDiskCacheDir(context, DISK_CACHE_SUBDIR);         mDiskCache = DiskLruCache.openCache(context, cacheDir, DISK_CACHE_SIZE);       }       /**      * 存放图片信息      */     class ImageRef {           /** 图片对应ImageView控件 */         ImageView imageView;         /** 图片URL地址 */         String url;         /** 图片缓存路径 */         String filePath;         /** 默认图资源ID */         int resId;         int width = 0;         int height = 0;           /**          * 构造函数          *          * @param imageView          * @param url          * @param resId          * @param filePath          */         ImageRef(ImageView imageView, String url, String filePath, int resId) {             this.imageView = imageView;             this.url = url;             this.filePath = filePath;             this.resId = resId;         }           ImageRef(ImageView imageView, String url, String filePath, int resId,                 int width, int height) {             this.imageView = imageView;             this.url = url;             this.filePath = filePath;             this.resId = resId;             this.width = width;             this.height = height;         }       }       /**      * 显示图片      *      * @param imageView      * @param url      * @param resId      */     public void displayImage(ImageView imageView, String url, int resId) {         if (imageView == null) {             return;         }         if (imageView.getTag() != null                 && imageView.getTag().toString().equals(url)) {             return;         }         if (resId >= 0) {             if (imageView.getBackground() == null) {                 imageView.setBackgroundResource(resId);             }             imageView.setImageDrawable(null);           }         if (url == null || url.equals("")) {             return;         }           // 添加url tag         imageView.setTag(url);           // 读取map缓存         Bitmap bitmap = mMemoryCache.get(url);         if (bitmap != null) {             setImageBitmap(imageView, bitmap, false);             return;         }           // 生成文件名         String filePath = urlToFilePath(url);         if (filePath == null) {             return;         }           queueImage(new ImageRef(imageView, url, filePath, resId));     }       /**      * 显示图片固定大小图片的缩略图，一般用于显示列表的图片，可以大大减小内存使用      *      * @param imageView 加载图片的控件      * @param url 加载地址      * @param resId 默认图片      * @param width 指定宽度      * @param height 指定高度      */     public void displayImage(ImageView imageView, String url, int resId,             int width, int height) {         if (imageView == null) {             return;         }         if (resId >= 0) {               if (imageView.getBackground() == null) {                 imageView.setBackgroundResource(resId);             }             imageView.setImageDrawable(null);           }         if (url == null || url.equals("")) {             return;         }           // 添加url tag         imageView.setTag(url);         // 读取map缓存         Bitmap bitmap = mMemoryCache.get(url + width + height);         if (bitmap != null) {             setImageBitmap(imageView, bitmap, false);             return;         }           // 生成文件名         String filePath = urlToFilePath(url);         if (filePath == null) {             return;         }           queueImage(new ImageRef(imageView, url, filePath, resId, width, height));     }       /**      * 入队，后进先出      *      * @param imageRef      */     public void queueImage(ImageRef imageRef) {           // 删除已有ImageView         Iterator<ImageRef> iterator = mImageQueue.iterator();         while (iterator.hasNext()) {             if (iterator.next().imageView == imageRef.imageView) {                 iterator.remove();             }         }           // 添加请求         mImageQueue.push(imageRef);         sendRequest();     }       /**      * 发送请求      */     private void sendRequest() {           // 开启图片加载线程         if (mImageLoaderHandler == null) {             HandlerThread imageLoader = new HandlerThread("image_loader");             imageLoader.start();             mImageLoaderHandler = new ImageLoaderHandler(                     imageLoader.getLooper());         }           // 发送请求         if (mImageLoaderIdle && mImageQueue.size() > 0) {             ImageRef imageRef = mImageQueue.pop();             Message message = mImageLoaderHandler.obtainMessage(MSG_REQUEST,                     imageRef);             mImageLoaderHandler.sendMessage(message);             mImageLoaderIdle = false;             mRequestQueue.add(imageRef);         }     }       /**      * 图片加载线程      */     class ImageLoaderHandler extends Handler {           public ImageLoaderHandler(Looper looper) {             super(looper);         }           public void handleMessage(Message msg) {             if (msg == null)                 return;               switch (msg.what) {               case MSG_REQUEST: // 收到请求                 Bitmap bitmap = null;                 Bitmap tBitmap = null;                 if (msg.obj != null && msg.obj instanceof ImageRef) {                       ImageRef imageRef = (ImageRef) msg.obj;                     String url = imageRef.url;                     if (url == null)                         return;                     // 如果本地url即读取sd相册图片，则直接读取，不用经过DiskCache                     if (url.toLowerCase().contains("dcim")) {                           tBitmap = null;                         BitmapFactory.Options opt = new BitmapFactory.Options();                         opt.inSampleSize = 1;                         opt.inJustDecodeBounds = true;                         BitmapFactory.decodeFile(url, opt);                         int bitmapSize = opt.outHeight * opt.outWidth * 4;                         opt.inSampleSize = bitmapSize / (1000 * 2000);                         opt.inJustDecodeBounds = false;                         tBitmap = BitmapFactory.decodeFile(url, opt);                         if (imageRef.width != 0 && imageRef.height != 0) {                             bitmap = ThumbnailUtils.extractThumbnail(tBitmap,                                     imageRef.width, imageRef.height,                                     ThumbnailUtils.OPTIONS_RECYCLE_INPUT);                             isFromNet = true;                         } else {                             bitmap = tBitmap;                             tBitmap = null;                         }                       } else                         bitmap = mDiskCache.get(url);                       if (bitmap != null) {                         // ToolUtil.log("从disk缓存读取");                         // 写入map缓存                         if (imageRef.width != 0 && imageRef.height != 0) {                             if (mMemoryCache.get(url + imageRef.width                                     + imageRef.height) == null)                                 mMemoryCache.put(url + imageRef.width                                         + imageRef.height, bitmap);                         } else {                             if (mMemoryCache.get(url) == null)                                 mMemoryCache.put(url, bitmap);                         }                       } else {                         try {                             byte[] data = loadByteArrayFromNetwork(url);                               if (data != null) {                                   BitmapFactory.Options opt = new BitmapFactory.Options();                                 opt.inSampleSize = 1;                                   opt.inJustDecodeBounds = true;                                 BitmapFactory.decodeByteArray(data, 0,                                         data.length, opt);                                 int bitmapSize = opt.outHeight * opt.outWidth                                         * 4;// pixels*3 if it's RGB and pixels*4                                             // if it's ARGB                                 if (bitmapSize > 1000 * 1200)                                     opt.inSampleSize = 2;                                 opt.inJustDecodeBounds = false;                                 tBitmap = BitmapFactory.decodeByteArray(data,                                         0, data.length, opt);                                 if (imageRef.width != 0 && imageRef.height != 0) {                                     bitmap = ThumbnailUtils                                             .extractThumbnail(                                                     tBitmap,                                                     imageRef.width,                                                     imageRef.height,                                                     ThumbnailUtils.OPTIONS_RECYCLE_INPUT);                                 } else {                                     bitmap = tBitmap;                                     tBitmap = null;                                 }                                   if (bitmap != null && url != null) {                                     // 写入SD卡                                     if (imageRef.width != 0                                             && imageRef.height != 0) {                                         mDiskCache.put(url + imageRef.width                                                 + imageRef.height, bitmap);                                         mMemoryCache.put(url + imageRef.width                                                 + imageRef.height, bitmap);                                     } else {                                         mDiskCache.put(url, bitmap);                                         mMemoryCache.put(url, bitmap);                                     }                                     isFromNet = true;                                 }                             }                         } catch (OutOfMemoryError e) {                         }                       }                   }                   if (mImageManagerHandler != null) {                     Message message = mImageManagerHandler.obtainMessage(                             MSG_REPLY, bitmap);                     mImageManagerHandler.sendMessage(message);                 }                 break;               case MSG_STOP: // 收到终止指令                 Looper.myLooper().quit();                 break;               }         }     }       /** UI线程消息处理器 */     private Handler mImageManagerHandler = new Handler() {           @Override         public void handleMessage(Message msg) {             if (msg != null) {                 switch (msg.what) {                   case MSG_REPLY: // 收到应答                       do {                         ImageRef imageRef = mRequestQueue.remove();                           if (imageRef == null)                             break;                           if (imageRef.imageView == null                                 || imageRef.imageView.getTag() == null                                 || imageRef.url == null)                             break;                           if (!(msg.obj instanceof Bitmap) || msg.obj == null) {                             break;                         }                         Bitmap bitmap = (Bitmap) msg.obj;                           // 非同一ImageView                         if (!(imageRef.url).equals((String) imageRef.imageView                                 .getTag())) {                             break;                         }                           setImageBitmap(imageRef.imageView, bitmap, isFromNet);                         isFromNet = false;                       } while (false);                       break;                 }             }             // 设置闲置标志             mImageLoaderIdle = true;               // 若服务未关闭，则发送下一个请求。             if (mImageLoaderHandler != null) {                 sendRequest();             }         }     };       /**      * 添加图片显示渐现动画      *      */     private void setImageBitmap(ImageView imageView, Bitmap bitmap,             boolean isTran) {         if (isTran) {             final TransitionDrawable td = new TransitionDrawable(                     new Drawable[] {                             new ColorDrawable(android.R.color.transparent),                             new BitmapDrawable(bitmap) });             td.setCrossFadeEnabled(true);             imageView.setImageDrawable(td);             td.startTransition(300);         } else {             imageView.setImageBitmap(bitmap);         }     }       /**      * 从网络获取图片字节数组      *      * @param url      * @return      */     private byte[] loadByteArrayFromNetwork(String url) {           try {               HttpGet method = new HttpGet(url);             HttpResponse response = myapp.getHttpClient().execute(method);             HttpEntity entity = response.getEntity();             return EntityUtils.toByteArray(entity);           } catch (Exception e) {             return null;         }       }       /**      * 根据url生成缓存文件完整路径名      *      * @param url      * @return      */     public String urlToFilePath(String url) {           // 扩展名位置         int index = url.lastIndexOf('.');         if (index == -1) {             return null;         }           StringBuilder filePath = new StringBuilder();           // 图片存取路径         filePath.append(myapp.getCacheDir().toString()).append('/');           // 图片文件名         filePath.append(MD5.Md5(url)).append(url.substring(index));           return filePath.toString();     }       /**      * Activity#onStop后，ListView不会有残余请求。      */     public void stop() {           // 清空请求队列         mImageQueue.clear();       }   }

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• 41楼：木法沙王 发表于 2014-04-10 17:26 回复此评论 //如果本地url即读取sd相册图片，则直接读取，不用经过DiskCache if (url.toLowerCase().contains("dcim") 建议把dcim改为mnt, 这样别的路经下图片也能加载了

• 42楼：迷途的小羔羊 发表于 2014-05-02 16:14 回复此评论 我他妈的非常感谢你，真心的

• 43楼：wgggfiy 发表于 2014-06-05 10:56 回复此评论 请问这个缓存何时可以清空呢？？我担心内存和磁盘会慢慢越积越大

• 44楼：巴顿将军 发表于 2014-07-19 18:16 回复此评论 什么东西呀，我跑不起来，看不到什么效果呢

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