Android的HttpUrlConnection网址无法在模拟器上工作

Question

我想从这个URL http://digitalcollections.tcd.ie/home/getMeta.php?pid=MS4418_021得到json对象作为字符串。它不起作用我在downloadUrl函数后出现错误。

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) 

它虽然这个androidhive网址http://api.androidhive.info/volley/person_object.json工作。 我是新来httpconnection下面是我的下载url功能。错误似乎显示在这一行HttpURLConnection conn =（HttpURLConnection）url.openConnection（）;在该行之后conn.getInputStream调试器（）表示IO异常和原因java.io.EOFException的：\ n未找到：大小= 0含量= ...

// 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; 
    } 

其它功能。

// 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 
     } 
    } 

加载json和解析器，解析器可能无法正常工作尚未测试它。

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模拟器上运行这个。

在此先感谢。

UPDATE：

不上Nexus_5_API_23模拟器工作吗？虽然它适用于三星GT-ST7500外接手机。希望它为模拟器工作。

Answer 1

问题是我的电脑上的防病毒/防火墙。这阻止了我的连接，这就是为什么它在外部电话而不是仿真器上工作。我禁用了我的防病毒/防火墙，它工作。这里有一个网络限制列表http://developer.android.com/tools/devices/emulator.html#networkinglimitations

Answer 2

我刚试过我的设备上的URL，没有得到任何错误。这是我使用的代码。

的接口，用于返回到UI线程

public interface AsyncResponse<T> { 
    void onResponse(T response); 
} 

---

一个通用的AsyncTask返回一个字符串 - 随意修改这个解析您的JSON并返回一个列表。

public class WebDownloadTask extends AsyncTask<String, Void, String> { 

    private AsyncResponse<String> callback; 

    public void setCallback(AsyncResponse<String> callback) { 
     this.callback = callback; 
    } 

    @Override 
    protected String doInBackground(String... params) { 
     String url = params[0]; 
     return readFromUrl(url); 
    } 

    @Override 
    protected void onPostExecute(String s) { 
     super.onPostExecute(s); 
     if (callback != null) { 
      callback.onResponse(s); 
     } else { 
      Log.w(WebDownloadTask.class.getSimpleName(), "The response was ignored"); 
     } 
    } 

    private String streamToString(InputStream is) throws IOException { 

     StringBuilder sb = new StringBuilder(); 
     BufferedReader rd = new BufferedReader(new InputStreamReader(is)); 
     String line; 
     while ((line = rd.readLine()) != null) { 
      sb.append(line); 
     } 
     return sb.toString(); 
    } 

    private String readFromUrl(String myWebpage) { 

     String response = null; 
     HttpURLConnection urlConnection = null; 

     try { 
      URL url = new URL(myWebpage); 

      urlConnection = (HttpURLConnection) url.openConnection(); 

      InputStream inputStream = urlConnection.getInputStream(); 
      if (inputStream != null) { 
       response = streamToString(inputStream); 
       inputStream.close(); 
      } 

     } catch (IOException e) { 
      e.printStackTrace(); 
     } finally { 
      if (urlConnection != null) { 
       urlConnection.disconnect(); 
      } 
     } 

     return response; 
    } 
} 

---

我的活动节调用的AsyncTask。

String url = "http://digitalcollections.tcd.ie/home/getMeta.php?pid=MS4418_021"; 

WebDownloadTask task = new WebDownloadTask(); 
task.setCallback(new AsyncResponse<String>() { 
    @Override 
    public void onResponse(String response) { 
     Toast.makeText(getApplicationContext(), response, Toast.LENGTH_SHORT).show(); 
    } 
}); 
task.execute(url);