图片缓存处理

public class ImageLoaders {

    String str = new String();

    MemoryCache memoryCache = new MemoryCache();
    FileCache fileCache;
    public static Bitmap bitmap;
    private Map<ImageView, String> imageViews = Collections
            .synchronizedMap(new HashMap<ImageView, String>());
    ArrayList<String> urllist = new ArrayList<String>();

    public ImageLoaders(Context context) {

        photoLoaderThread.setPriority(Thread.NORM_PRIORITY - 1);

        fileCache = new FileCache(context);
    }

    final int stub_id = R.drawable.icon;

    public void DisplayImage(String url, Activity activity, ImageView imageView) {
        imageViews.put(imageView, url);

        urllist.add(url);

        if (urllist.size() > 1) {
            Iterator it = urllist.iterator();
            int i = 0;
            while (it.hasNext()) {

                String ss = (String) it.next();


                if (i < urllist.size() - 1) {
                    if (memoryCache.get(ss) != null
                            && !memoryCache.get(ss).isRecycled()) {

                        Bitmap bit = memoryCache.get(ss);

                        bit = null;

                    }

                }

                i++;
            }
            urllist.clear();
        }

        bitmap = memoryCache.get(url);

        if (bitmap != null) {

            imageView.setImageBitmap(bitmap);

        } else {
            queuePhoto(url, activity, imageView);
            imageView.setImageResource(stub_id);
        }

    }

    private void queuePhoto(String url, Activity activity, ImageView imageView) {
        photosQueue.Clean(imageView);
        PhotoToLoad p = new PhotoToLoad(url, imageView);
        synchronized (photosQueue.photosToLoad) {
            photosQueue.photosToLoad.push(p);
            photosQueue.photosToLoad.notifyAll();
        }

        // start thread if it's not started yet
        if (photoLoaderThread.getState() == Thread.State.NEW)
            photoLoaderThread.start();
    }

    private Bitmap getBitmap(String url) {
        File f = fileCache.getFile(url);

        // from SD cache
        Bitmap b = decodeFile(f);
        if (b != null)
            return b;

        // from web
        try {
            Bitmap bitmap = null;
            URL imageUrl = new URL(url);
            HttpURLConnection conn = (HttpURLConnection) imageUrl
                    .openConnection();
            conn.setConnectTimeout(30000);
            conn.setReadTimeout(30000);
            InputStream is = conn.getInputStream();
            OutputStream os = new FileOutputStream(f);
            com.monsou.photography.publicmethod.Utils.CopyStream(is, os);
            os.close();
            bitmap = decodeFile(f);
            return bitmap;
        } catch (Exception ex) {
            ex.printStackTrace();
            return null;
        }
    }

    // decodes image and scales it to reduce memory consumption
    private Bitmap decodeFile(File f) {
        try {
            // decode image size
            BitmapFactory.Options o = new BitmapFactory.Options();
            o.inJustDecodeBounds = true;
            BitmapFactory.decodeStream(new FileInputStream(f), null, o);

            // Find the correct scale value. It should be the power of 2.
            final int REQUIRED_SIZE = 240;
            int width_tmp = o.outWidth, height_tmp = o.outHeight;
            int scale = 1;
            while (true) {
                if (width_tmp / 2 < REQUIRED_SIZE
                        || height_tmp / 2 < REQUIRED_SIZE)
                    break;
                width_tmp /= 2;
                height_tmp /= 2;
                scale *= 2;
            }

            // decode with inSampleSize
            BitmapFactory.Options o2 = new BitmapFactory.Options();
            o2.inSampleSize = scale;
            return BitmapFactory.decodeStream(new FileInputStream(f), null, o2);
        } catch (FileNotFoundException e) {
        }
        return null;
    }

    // Task for the queue
    private class PhotoToLoad {
        public String url;
        public ImageView imageView;

        public PhotoToLoad(String u, ImageView i) {
            url = u;
            imageView = i;
        }
    }

    PhotosQueue photosQueue = new PhotosQueue();

    public void stopThread() {
        photoLoaderThread.interrupt();
    }

    // stores list of photos to download
    class PhotosQueue {
        private Stack<PhotoToLoad> photosToLoad = new Stack<PhotoToLoad>();

        // removes all instances of this ImageView
        public void Clean(ImageView image) {
            for (int j = 0; j < photosToLoad.size();) {
                if (photosToLoad.get(j).imageView == image)
                    photosToLoad.remove(j);
                else
                    ++j;
            }
        }
    }

    class PhotosLoader extends Thread {
        public void run() {
            try {
                while (true) {
                    // thread waits until there are any images to load in the
                    // queue
                    if (photosQueue.photosToLoad.size() == 0)
                        synchronized (photosQueue.photosToLoad) {
                            photosQueue.photosToLoad.wait();
                        }
                    if (photosQueue.photosToLoad.size() != 0) {
                        PhotoToLoad photoToLoad;
                        synchronized (photosQueue.photosToLoad) {
                            photoToLoad = photosQueue.photosToLoad.pop();
                        }
                        Bitmap bmp = getBitmap(photoToLoad.url);
                        memoryCache.put(photoToLoad.url, bmp);
                        String tag = imageViews.get(photoToLoad.imageView);
                        if (tag != null && tag.equals(photoToLoad.url)) {
                            BitmapDisplayer bd = new BitmapDisplayer(bmp,
                                    photoToLoad.imageView);
                            Activity a = (Activity) photoToLoad.imageView
                                    .getContext();
                            a.runOnUiThread(bd);
                        }
                    }
                    if (Thread.interrupted())
                        break;
                }
            } catch (InterruptedException e) {
                // allow thread to exit
            }
        }
    }

    PhotosLoader photoLoaderThread = new PhotosLoader();

    // Used to display bitmap in the UI thread
    class BitmapDisplayer implements Runnable {
        Bitmap bitmap;
        ImageView imageView;

        public BitmapDisplayer(Bitmap b, ImageView i) {
            bitmap = b;
            imageView = i;
        }

        public void run() {
            if (bitmap != null) {

                imageView.setImageBitmap(bitmap);

            } else {

                imageView.setImageResource(stub_id);
            }

        }

    }

    public void clearCache() {
        memoryCache.clear();
        fileCache.clear();
    }

}

在适配器中调用

class GalleryAdapter extends BaseAdapter {
        Context c;
        private ImageLoaders imageLoader;

        public GalleryAdapter(Context c) {
            imageLoader = new ImageLoaders(c);
            this.c = c;
        }

        @Override
        public int getCount() {
            return productList.getAllItems().size();
        }

        @Override
        public Object getItem(int position) {
            return productList.getAllItems().get(position);
        }

        @Override
        public long getItemId(int position) {
            return position;
        }

        @Override
        public View getView(int position, View convertView, ViewGroup parent) {
            ViewHolder holder = null;
            if (convertView == null) {
                holder = new ViewHolder();
                convertView = LayoutInflater.from(c).inflate(
                        R.layout.product_tiem_01, parent, false);
                holder.imagerView = (ImageView) convertView
                        .findViewById(R.id.imageView1);
                convertView.setTag(holder);
            } else {
                holder = (ViewHolder) convertView.getTag();
            }
            String str_iv = productList.getItem(position).getSmallimg();
            imageLoader.DisplayImage(str_iv, ProductActivity.this, holder.imagerView);
            return convertView;
        }

    }

    public static class ViewHolder {
        ImageView imagerView;
    }