有什么方法可以加速Android上的大规模图像下载？

Question

我有大约100个自定义对象，每个对象需要从网上下载的两个图像（徽标和圆形/圆形徽标）供离线使用。我目前正在使用AsyncTask。我有两个url的ArrayLists，每个类型的图像一个，我作为参数发送。整个过程大约需要一分钟，用户需要等到它完成，因为应用程序围绕下载的项目。有什么方法可以加快速度吗？当我在iOS中实现它时，在同一网络上大约需要10秒钟。

new LogoDownloadTask(resources).execute(logoURLs, roundLogoURLs);

// ...

private class LogoDownloadTask extends AsyncTask<ArrayList, Integer, Void> {

    private ArrayList<Organization> resources;

    public LogoDownloadTask(ArrayList<Organization> resources) {
        this.resources = resources;
    }

    @Override
    protected Void doInBackground(ArrayList... urls) {
        try {

            // Download logos
            for (int i = 0; i < urls[0].size(); i++) {
                URL url = (URL)urls[0].get(i);
                Bitmap bm = downloadImage(url);
                Organization org = resources.get(i);
                if (bm == null) {
                    Log.v(TAG, "ERROR DOWNLOADING LOGO FOR " + org.getName());
                } else {
                    org.setLogo(bm);
                }
            }

            // Download round logos
            for (int i = 0; i < urls[1].size(); i++) {
                URL url = (URL)urls[0].get(i);
                Bitmap bm = downloadImage(url);
                Organization org = resources.get(i);
                if (bm == null) {
                    Log.v(TAG, "ERROR DOWNLOADING ROUND LOGO FOR " + org.getName());
                } else {
                    org.setRoundLogo(bm);
                }
            }
        } catch (Exception e) {
            Log.v(TAG, "FAILURE REACHING SERVER");
        }
        return null;
    }

    @Override
    protected void onPostExecute(Void v) { /* ... */ }

    private Bitmap downloadImage(URL url) {
        try {
            HttpURLConnection connection = (HttpURLConnection) url.openConnection();
            InputStream inputStream = connection.getInputStream();
            Bitmap bitmap = BitmapFactory.decodeStream(inputStream);
            inputStream.close();
            return bitmap;
        } catch (IOException e) {
            return null;
        }
    }
}