xUtils下载文件时总大小返回-1问题

xUtils下载文件时无法返回总大小是因为Accept-Encoding头设置问题，需要设置Accept-Encoding头为“identity”，设置方法如下：

HttpUtils http = new HttpUtils();
((DefaultHttpClient)http.getHttpClient()).addRequestInterceptor(new HttpRequestInterceptor() {
			@Override
			public void process(org.apache.http.HttpRequest httpRequest, HttpContext httpContext) throws org.apache.http.HttpException, IOException {
				if (!httpRequest.containsHeader("Accept-Encoding")) {
					httpRequest.addHeader("Accept-Encoding", "identity");
				} else {
					httpRequest.setHeader("Accept-Encoding", " identity");
				}
			}
		});