Question

我不是专业开发的android。我想从我的服务器下载一个JSON对象，但只有我能找到的代码是这样的：

    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int len = 500，我返回的json被裁剪为500个字符。我尝试过更改为一个很好的数字，但它最后会添加空格。如何知道InputSteam包含的字符串的大小？

由于

Answer 1

您可以检查回复的Content-Length标头值：

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());
}
}

或者你可以在这样的缓冲读卡器中做出回应：

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);
            }

Answer 2

Yout可以使用Apache Commons IO IOUtils.toString将InputStream转换为String或使用Gson直接从输入流中读取对象：

 return gson.fromJson(new InputStreamReader(inputStream), YourType.class);

Android - 以http响应的字符大小

2 个答案: