Android：reader.readLine（）返回NULL

Question

該方法創建一個HTTP連接，但讀取數據時爲reader.readLine() returns NULL。

protected String doInBackground(String... strings) { 


     try { 

      // Enter URL address where your php file resides 
      url = new URL("http://makemyweb.xyz/mobile/login.inc.php"); 
      Log.d(TAG, "Connected to "+ url); 
     } catch (MalformedURLException e) { 
      // TODO Auto-generated catch block 
      e.printStackTrace(); 
      return "exception"; 
     } 

     try { 
      // Setup HttpURLConnection class to send and receive data from php and mysql 
      conn = (HttpURLConnection)url.openConnection(); 
      conn.setReadTimeout(READ_TIMEOUT); 
      conn.setConnectTimeout(CONNECTION_TIMEOUT); 
      conn.setRequestMethod("GET"); 

      // setDoInput and setDoOutput method depict handling of both send and receive 
      conn.setDoInput(true); 
      conn.setDoOutput(true); 

      // Append parameters to URL 
      Uri.Builder builder = new Uri.Builder() 
        .appendQueryParameter("email", strings[0]) 
        .appendQueryParameter("pass", strings[1]); 
      String query = builder.build().getEncodedQuery(); 
      Log.d(TAG, "Q: "+query); 
      // Open connection for sending data 
      OutputStream os = conn.getOutputStream(); 
      BufferedWriter writer = new BufferedWriter(
        new OutputStreamWriter(os, "UTF-8")); 
      writer.write(query); 
      writer.flush(); 
      writer.close(); 
      os.close(); 
      conn.connect(); 

     } catch (IOException e1) { 
      // TODO Auto-generated catch block 
      e1.printStackTrace(); 
      return "exception"; 
     } 

     try { 
      int response_code = conn.getResponseCode(); 

      // Check if successful connection made 
      if (response_code == HttpURLConnection.HTTP_OK) { 

       // Read data sent from server 
       InputStream input = conn.getInputStream(); 
       BufferedReader reader = new BufferedReader(new InputStreamReader(input)); 
       StringBuilder result = new StringBuilder(); 
       String line; 

       while ((line = reader.readLine()) != null) { 
        result.append(line); 
       } 
       // Pass data to onPostExecute method 
       return(result.toString()); 
      }else{ 
       return("unsuccessful"); 
      } 
     } catch (IOException e) { 
      e.printStackTrace(); 
      return "exception"; 
     } finally { 
      conn.disconnect(); 
     } 

    } 

Answer 1

我試過你的代碼，它不返回null。下面是完整的代碼：

private final String TAG = this.getClass().getSimpleName(); 
private URL url; 
private HttpURLConnection conn; 
private static final int READ_TIMEOUT = 10_000; 
private static final int CONNECTION_TIMEOUT = 10_000; 

private void testConnection() { 
    AsyncTask<String, Integer, String> asyncTask = new AsyncTask<String, Integer, String>() { 
     protected String doInBackground(String... strings) { 
      try { 
       // Enter URL address where your php file resides 
       url = new URL("http://makemyweb.xyz/mobile/login.inc.php"); 
       Log.d(TAG, "Connected to " + url); 
      } catch (MalformedURLException e) { 
       // TODO Auto-generated catch block 
       e.printStackTrace(); 
       return "exception"; 
      } 

      try { 
       // Setup HttpURLConnection class to send and receive data from php and mysql 
       conn = (HttpURLConnection) url.openConnection(); 
       conn.setReadTimeout(READ_TIMEOUT); 
       conn.setConnectTimeout(CONNECTION_TIMEOUT); 
       conn.setRequestMethod("GET"); 

       // setDoInput and setDoOutput method depict handling of both send and receive 
       conn.setDoInput(true); 
       conn.setDoOutput(true); 

       // Append parameters to URL 
       Uri.Builder builder = new Uri.Builder() 
         .appendQueryParameter("email", strings[0]) 
         .appendQueryParameter("pass", strings[1]); 
       String query = builder.build().getEncodedQuery(); 
       Log.d(TAG, "Q: " + query); 
       // Open connection for sending data 
       OutputStream os = conn.getOutputStream(); 
       BufferedWriter writer = new BufferedWriter(
         new OutputStreamWriter(os, "UTF-8")); 
       writer.write(query); 
       writer.flush(); 
       writer.close(); 
       os.close(); 
       conn.connect(); 
      } catch (IOException e1) { 
       // TODO Auto-generated catch block 
       e1.printStackTrace(); 
       return "exception"; 
      } 

      try { 
       int response_code = conn.getResponseCode(); 

       // Check if successful connection made 
       if (response_code == HttpURLConnection.HTTP_OK) { 

        // Read data sent from server 
        InputStream input = conn.getInputStream(); 
        BufferedReader reader = new BufferedReader(new InputStreamReader(input)); 
        StringBuilder result = new StringBuilder(); 
        String line; 

        while ((line = reader.readLine()) != null) { 
         result.append(line); 
        } 
        // Pass data to onPostExecute method 
        return (result.toString()); 
       } else { 
        return ("unsuccessful"); 
       } 
      } catch (IOException e) { 
       e.printStackTrace(); 
       return "exception"; 
      } finally { 
       conn.disconnect(); 
      } 

     } 

     @Override 
     protected void onPostExecute(String s) { 
      Log.d(TAG, "result : " + s); 
     } 
    }; 

    asyncTask.execute("someemail@someweb.com", "password"); 
} 

並確保您有

<uses-permission android:name="android.permission.INTERNET" /> 

你的清單文件