java - Android - HTTP 响应的字符大小

Question

我不是专业开发 Android 的人。我想从我的服务器下载一个 JSON 对象，但我只能找到这样的代码:

    private String downloadUrl(String myurl) throws IOException {
        InputStream is = null;
        // Only display the first 500 characters of the retrieved
        // web page content.
        int len = 500;

        try {
            URL url = new URL(myurl);
            HttpURLConnection conn = (HttpURLConnection) url.openConnection();
            conn.setReadTimeout(10000 /* milliseconds */);
            conn.setConnectTimeout(15000 /* milliseconds */);
            conn.setRequestMethod("GET");
            conn.setDoInput(true);
            // Starts the query
            conn.connect();
            int response = conn.getResponseCode();
            Log.d("ServerConnection", "The response is: " + response);
            is = conn.getInputStream();;
            //is.
            // Convert the InputStream into a string
            String contentAsString = readIt(is, len);
            return contentAsString;

            // Makes sure that the InputStream is closed after the app is
            // finished using it.
        } catch (MalformedURLException e) {
            //
            return "error";
        } catch (IOException e) {
            //
            return "error";
        } finally {
            if (is != null) {
                is.close();
            }
        }
    }

它工作正常，我无法理解。但它有一个 int len = 500，并且我返回的 json 被裁剪为 500 个字符。我尝试更改为一个很大的数字，但它在末尾添加了空格。我如何知道 InputSteam 包含的字符串的字符大小？

谢谢

Answer 1

您可以检查响应的 Content-Length header 值:

Map<String, List<String>> headers = connection.getHeaderFields();
for (Entry<String, List<String>> header : headers.entrySet()) {
if(header.getKey().equals("Content-Legth")){
len=Integer.parseInt(header.getValue());
}
}

或者您可以在缓冲阅读器中做出响应，如下所示:

InputStream is = connection.getInputStream();
InputStreamReader reader = new InputStreamReader(is);
            StringBuilder builder = new StringBuilder();
            int c = 0;
            while ((c = reader.read()) != -1) {
                builder.append((char) c);
            }