android图片异步加载到本地

package com.example.health.util;import java.lang.ref.SoftReference;import java.util.HashMap;import java.util.HashSet;import java.util.Map;import java.util.concurrent.ExecutorService;import java.util.concurrent.Executors;import android.content.Context;import android.graphics.Bitmap;import android.os.Handler;import android.util.Log;public class AsyncImageLoader {//保存正在下载的图片URL集合，避免重复下载用private static HashSet<String> sDownloadingSet;//软引用内存缓存private static Map<String,SoftReference<Bitmap>> sImageCache; //图片三种获取方式管理者，网络URL获取、内存缓存获取、外部文件缓存获取private static LoaderImpl impl;//线程池相关private static ExecutorService sExecutorService;//通知UI线程图片获取ok时使用private Handler handler; /** * 异步加载图片完毕的回调接口 */public interface ImageCallback{/** * 回调函数 * @param bitmap: may be null! * @param imageUrl  */public void onImageLoaded(Bitmap bitmap, String imageUrl);}static{sDownloadingSet = new HashSet<String>();sImageCache = new HashMap<String,SoftReference<Bitmap>>();impl = new LoaderImpl(sImageCache);}public AsyncImageLoader(Context context){handler = new Handler();startThreadPoolIfNecessary();String defaultDir = context.getCacheDir().getAbsolutePath();setCachedDir(defaultDir);}/** * 是否缓存图片至/data/data/package/cache/目录 * 默认不缓存 */public void setCache2File(boolean flag){impl.setCache2File(flag);}/** * 设置缓存路径，setCache2File(true)时有效 */public void setCachedDir(String dir){impl.setCachedDir(dir);}/**开启线程池*/public static void startThreadPoolIfNecessary(){if(sExecutorService == null || sExecutorService.isShutdown() || sExecutorService.isTerminated()){sExecutorService = Executors.newFixedThreadPool(3);//sExecutorService = Executors.newSingleThreadExecutor();}}/** * 异步下载图片，并缓存到memory中 * @param url * @param callbacksee ImageCallback interface */public void downloadImage(final String url, final ImageCallback callback){downloadImage(url, true, callback);}/** *  * @param url * @param cache2Memory 是否缓存至memory中 * @param callback */public void downloadImage(final String url, final boolean cache2Memory, final ImageCallback callback){if(sDownloadingSet.contains(url)){Log.i("AsyncImageLoader", "###该图片正在下载，不能重复下载！");return;}Bitmap bitmap = impl.getBitmapFromMemory(url);if(bitmap != null){if(callback != null){callback.onImageLoaded(bitmap, url);}}else{//从网络端下载图片sDownloadingSet.add(url);sExecutorService.submit(new Runnable(){@Overridepublic void run() {final Bitmap bitmap = impl.getBitmapFromUrl(url, cache2Memory);handler.post(new Runnable(){@Overridepublic void run(){if(callback != null)callback.onImageLoaded(bitmap, url);sDownloadingSet.remove(url);}});}});}}/** * 预加载下一张图片，缓存至memory中 * @param url  */public void preLoadNextImage(final String url){//将callback置为空，只将bitmap缓存到memory即可。downloadImage(url, null);}}

    private void showImage(String imgUrl) {        if(null==LoadingActivity.userList) {        image.setImageResource(images[2]);        } else {            //for test            AsyncImageLoader loader = new AsyncImageLoader(getApplicationContext());                        //将图片缓存至外部文件中            loader.setCache2File(false);//false            //设置外部缓存文件夹            loader.setCachedDir(this.getCacheDir().getAbsolutePath());                        //下载图片，第二个参数是否缓存至内存中            loader.downloadImage(imgUrl, true/*false*/, new AsyncImageLoader.ImageCallback() {    @Override    public void onImageLoaded(Bitmap bitmap, String imageUrl) {    if(bitmap != null){    image.setImageBitmap(bitmap);    }else{    //下载失败，设置默认图片    image.setImageResource(images[2]);    }    }    });        }    }

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