@Override
    protected void onCachePercentsAvailableChanged(int percents) {
        if (listener != null) {
            listener.onCacheAvailable(cache.file, source.getUrl(), percents);
        }
    }
{@link ProxyCache} that read http url and writes data to {@link Socket}
VideoCache/src/main/java/com/yc/videocache/HttpProxyCache.java