Android-从URL解析JSON明文返回空值，但连接正常

Question

我正在从URL解析数据。我正在使用下面的代码在logcat中获取明文数据。但是，尽管没有问题，但显示为空。

class RetrieveFeedTask extends AsyncTask<String, Void, String> {

        @Override
        protected String doInBackground(String... arg0) {
            int responseCode = -1;
            //String responseData;
            try {
                URL retailerUrl = new URL("http://clients.appatlantis.com/soldy/wp-json/wp/v2/soldy-clients");
                HttpURLConnection connection = (HttpURLConnection) retailerUrl.openConnection();
                connection.connect();

                responseCode = connection.getResponseCode();


                if (responseCode == HttpURLConnection.HTTP_OK) {
                    InputStream inputStream = connection.getInputStream();

                    Reader reader = new InputStreamReader(inputStream);
                    int contentLength = connection.getContentLength();
                    char[] charArray = new char[contentLength];
                    reader.read(charArray);
                    String responseData = new String(charArray);
                    data = responseData;
                    Log.v(TAG, "Parse Data "+data);
                } else {
                    Log.e(TAG, "Parse Data Failed");
                }

            } catch (MalformedURLException e) {
                Log.e(TAG, "URL Exeption: ", e);
            } catch (IOException e) {
                Log.e(TAG, "IO URL Exeption: ", e);
            } catch (Exception e) {
                Log.e(TAG, "Exeption Caught: ", e);
            }

            return "Response Code "+data;
        }

        @Override
        protected void onPostExecute(String s) {
            super.onPostExecute(s);

            Log.v(TAG, "Parse Data "+data);

        }
    }

这里是完整的回溯。请注意，错误将以NegetiveArraySizeException的形式抛出，因为没有结果。

2020-04-12 02:41:03.853 7262-7373/com.appatlantis.jsonsample D/NetworkSecurityConfig: No Network Security Config specified, using platform default
2020-04-12 02:41:03.867 7262-7373/com.appatlantis.jsonsample W/System: ClassLoader referenced unknown path: system/framework/mediatek-cta.jar
2020-04-12 02:41:03.870 7262-7373/com.appatlantis.jsonsample I/System.out: e:java.lang.ClassNotFoundException: com.mediatek.cta.CtaHttp
2020-04-12 02:41:03.881 7262-7373/com.appatlantis.jsonsample W/System: ClassLoader referenced unknown path: system/framework/mediatek-cta.jar
2020-04-12 02:41:03.884 7262-7373/com.appatlantis.jsonsample I/System.out: e:java.lang.ClassNotFoundException: com.mediatek.cta.CtaHttp
2020-04-12 02:41:03.945 7262-7373/com.appatlantis.jsonsample I/System.out: [OkHttp] sendRequest>>
2020-04-12 02:41:03.947 7262-7373/com.appatlantis.jsonsample I/System.out: [OkHttp] sendRequest<<
2020-04-12 02:41:04.402 7262-7373/com.appatlantis.jsonsample E/MainActivity: Exeption Caught: 
    java.lang.NegativeArraySizeException: -1
        at com.appatlantis.jsonsample.MainActivity$RetrieveFeedTask.doInBackground(MainActivity.java:85)
        at com.appatlantis.jsonsample.MainActivity$RetrieveFeedTask.doInBackground(MainActivity.java:58)
        at android.os.AsyncTask$2.call(AsyncTask.java:333)
        at java.util.concurrent.FutureTask.run(FutureTask.java:266)
        at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:245)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1167)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:641)
        at java.lang.Thread.run(Thread.java:764)
2020-04-12 02:41:04.402 7262-7262/com.appatlantis.jsonsample V/MainActivity: Parse Data null

Answer 1

之所以会这样，是因为connection.getContentLength()返回-1。发生这种情况是因为内容长度未知。更具体地说，服务器未在响应消息中设置“ Content-Length”标头。

您可以做的是

                InputStream inputStream = connection.getInputStream();
                Scanner s = new Scanner(inputStream).useDelimiter("\\A");
                data = s.hasNext() ? s.next() : "";
                Log.v(TAG, "Parse Data " + data);

这将起作用。

Answer 2

尝试此解决方案

向<application中的AndroidManifest.xml标签添加以下属性：

android:usesCleartextTraffic="true"

如果需要更多详细信息，请please see this answer