Android HttpUrlConnection Url 在模拟器上不起作用

Question

我正在尝试从这个 url http://digitalcollections.tcd.ie/home/getMeta.php?pid=MS4418_021 获取 json 对象作为字符串.它不起作用我在 downloadUrl 函数后收到错误。

java.io.IOException: unexpected end of stream on Connection{digitalcollections.tcd.ie:80, proxy=DIRECT@ hostAddress=134.226.115.12 cipherSuite=none protocol=http/1.1} (recycle count=0)

虽然它确实适用于这个 androidhive url http://api.androidhive.info/volley/person_object.json .我是 httpconnection 的新手，下面是我的下载 url 函数。错误似乎显示在这一行 HttpURLConnection conn = (HttpURLConnection) url.openConnection();在该行之后的调试器中 conn.getInputStream() 显示 IO 异常和原因 java.io.EOFException:\n not found: size=0 content=...

 // Given a string representation of a URL, sets up a connection and gets
 // an input stream.
 private InputStream downloadUrl(String urlString) throws IOException {
        URL url = new URL(urlString);
        HttpURLConnection conn = (HttpURLConnection) url.openConnection();
        conn.setReadTimeout(20000 /* milliseconds */);
        conn.setConnectTimeout(30000 /* milliseconds */);
        conn.setRequestMethod("GET");
        //conn.setDoInput(true);        
        // Starts the query
        conn.connect();
        InputStream stream = conn.getInputStream();
        return stream;
    }

其他功能。

 // Uses AsyncTask to create a task away from the main UI thread. This task takes a
    // URL string and uses it to create an HttpUrlConnection. Once the connection
    // has been established, the AsyncTask downloads the contents of the webpage as
    // an InputStream. Finally, the InputStream is converted into a string, which is
    // displayed in the UI by the AsyncTask's onPostExecute method.
    private class DownloadXMLTask extends AsyncTask<String, Void, List<Entry>> {
        private String urlFront = "";
        @Override
        protected List<Entry> doInBackground(String... urls) {
            // params comes from the execute() call: params[0] is the url.
            try {
                    return loadJsonFromNetwork(urls[0]);
                } catch (IOException e) {
                    Log.d(TAG, "Unable to retrieve web page. URL may be invalid.");
                    return null;
                } catch (JSONException e) {
                    Log.d(TAG, "XMLPULLPARSER ERROR IN download json task function");
                    return null;
                }
            }

        }
        // onPostExecute displays the results of the AsyncTask.
        @Override
        protected void onPostExecute(List<Entry> result) {
            //post execution stuff
        }
    }

正在加载 json 和解析器，解析器可能无法正常工作尚未测试。

 private List<Entry> loadJsonFromNetwork(String urlString) throws IOException, JSONException {
        InputStream stream = null;
        int len = 20000; //max amount of characters to display in string
        List<Entry> entries = new ArrayList<Entry>();

        try {
            stream = downloadUrl(urlString);  //IOException
            String jsonStr = readit(stream,len);
            if(jsonStr.equals(null)){
                Log.d(TAG, "ERROR json string returned null");
                return entries;
            }
            JSONObject jsonObj = new JSONObject(jsonStr);

            //Not sure if the json parser works yet haven't got that far 
            // Getting JSON Array node
            identifier = jsonObj.getJSONArray("identifier");

            // looping through All Contacts
            for (int i = 0; i < identifier.length(); i++) {
                JSONObject c = identifier.getJSONObject(i);

                String id = c.getString("type");
                if(id.equals("DRIS_FOLDER")) {
                    String folder = c.getString("$");
                    entries.add(new Entry(null,null,null,folder));
                }
            }

            // Makes sure that the InputStream is closed after the app is
            // finished using it.
          //This is where IOexception is called and stream is null
        } catch (IOException e) {
            Log.d(TAG, "Unable to retrieve json web page. URL may be invalid."+ e.toString());
            return entries;
        }
        finally {
            if (stream != null) {
                stream.close();
            }
        }
        return entries;
    }

我在 Nexus_5_API_23 模拟器上运行它。

提前致谢。

更新:

在 Nexus_5_API_23 模拟器上不起作用？？虽然它适用于三星 GT-ST7500 外接电话。希望它适用于模拟器。

Answer 1

问题是我电脑上的防病毒/防火墙。它阻止了我的连接，这就是它在外部电话而不是模拟器上工作的原因。我禁用了我的防病毒/防火墙并且它起作用了。这里有一个网络限制列表 http://developer.android.com/tools/devices/emulator.html#networkinglimitations