Android图片异步加载

public void run() {

            Process.setThreadPriority(Process.THREAD_PRIORITY_BACKGROUND);

            final Handler h = mHandler;
            Bitmap bitmap = null;
            Throwable throwable = null;

            h.sendMessage(Message.obtain(h, ON_START));

            try {
                if (TextUtils.isEmpty(mUrl)) {
                    throw new Exception("The given URL cannot be null or empty");
                }

                // 如果自定义了加载方法,则用自定义的方法
                if (mLoadMethod != null) {
                    bitmap = mLoadMethod.load(mUrl);
                } else {

                    InputStream inputStream = null;

                    // Asset
                    if (mUrl.startsWith("file:///android_asset/")) {
                        inputStream = sAssetManager.open(mUrl.replaceFirst(
                                "file:///android_asset/", ""));
                    }
                    // File
                    else if (mUrl.startsWith("file:///") || mUrl.startsWith("/")) {
                        if (mUrl.startsWith("file:///"))
                            mUrl = mUrl.replaceFirst("file:///", "/");
                        inputStream = new FileInputStream(mUrl);
                    }
                    // NetWork
                    else {
                        // 在用URL类加载图片时，发现有的机型上面通过URL类获得的InputStream解析获得的图片总是null，故使用HttpClient
                        HttpGet httpRequest = new HttpGet(mUrl);
                        HttpClient httpclient = new DefaultHttpClient();
                        HttpParams httpParams = new BasicHttpParams();
                        HttpConnectionParams.setConnectionTimeout(httpParams, 5000);
                        HttpConnectionParams.setSoTimeout(httpParams, 5000);
                        httpRequest.setParams(httpParams);
                        HttpResponse response = (HttpResponse)httpclient.execute(httpRequest);
                        HttpEntity entity = response.getEntity();
                        BufferedHttpEntity bufHttpEntity = new BufferedHttpEntity(entity);
                        InputStream instream = bufHttpEntity.getContent();
                        BufferedInputStream bi = new BufferedInputStream(instream);
                        inputStream = bi;
                    }

                    // 虽然AsyncImageView中有设置BitmapFactory.Options的方法，但一般情况下都未知图片的大小，也就无法计算相应的inSampleSize，
                    // 也就无法设置相应的BitmapFactory.Options，所以一般情况下还是根据自己的需要自定义LoadMethod为好
                    bitmap = BitmapFactory.decodeStream(inputStream, null,
                            (mOptions == null) ? sDefaultOptions : mOptions);
                    inputStream.close();
                }
                if (mBitmapProcessor != null && bitmap != null) {
                    final Bitmap processedBitmap = mBitmapProcessor.processImage(bitmap);
                    if (processedBitmap != null) {
                        bitmap.recycle();
                        bitmap = processedBitmap;
                    }
                }

            } catch (Exception e) {
                Log.e(LOG_TAG, "Error while fetching image", e);
                throwable = e;
            }

            if (bitmap == null) {
                if (throwable == null) {
                    throwable = new Exception("Skia image decoding failed");
                }
                h.sendMessage(Message.obtain(h, ON_FAIL, throwable));
            } else {
                h.sendMessage(Message.obtain(h, ON_END, bitmap));
                if (mCache != null) {
                    mCache.writeCache(TextUtils.isEmpty(mCacheKey) ? mUrl : mCacheKey, bitmap);
                }
            }
        }

/**
     * 设置要加载的图片的路径, 可为网络路径, Asset文件路径(file:///android_asset), 本地图片路径(file:///或/)
     * 
     * @param path 要加载的图片的路径, 若为null则加载默认图片
     * @param loadMethod 自定义的图片加载的方法, 可以null, 使用默认的加载方法
     * @param cacheKey 缓存key
     */
    public void setPath(String path, LoadMethod loadMethod, String cacheKey) {

        // Check the url has changed
        if (mBitmap != null && path != null && path.equals(mUrl)) { // TODO mBitmap != null necessary?
            return;
        }

        stopLoading();
        mUrl = path;
        mCacheKey = cacheKey;
        mLoadMethod = loadMethod;

        // Setting the url to an empty string force the displayed image to the
        // default image
        if (TextUtils.isEmpty(mUrl)) {
            mBitmap = null;
            setDefaultImage();
        } else {
            if (!mPaused) {
                reload();
            } else {
                // We're paused: let's look in a synchronous and efficient cache
                // prior using the default image.
                mBitmap = readCache(); // TODO 可能会耗时间
                if (mBitmap != null) {
                    setImageBitmap(mBitmap);
                } else {
                    setDefaultImage();
                }
            }
        }
    }

public void reload(boolean force) {
        if (mRequest == null && mUrl != null) {

            // Prior downloading the image ... let's look in a cache !
            mBitmap = null;
            if (!force) {
                // This may take a long time.
                mBitmap = readCache();
            }

            if (mBitmap != null) {
                setImageBitmap(mBitmap);
                return;
            }

            setDefaultImage();
            mRequest = new ImageRequest(mUrl, this, mImageProcessor, mOptions, mCacheKey);
            mRequest.load(getContext(), mLoadMethod);
            if (ImageLoader.getInstance() != null && ImageLoader.getInstance().getCache() == null) {
                ImageLoader.getInstance().setCache(mCache);
            }
        }

    private Bitmap readCache() {
        if (mCache != null)
            return mCache.readCache(TextUtils.isEmpty(mCacheKey) ? mUrl : mCacheKey);
        return null;
    }