مشکل با webservice

سلام دوستان و بزرگواران.

من تو  webservice مشکل دارم . سمت php درست درست کار میکنه و خروجی و چاپ میکنه ولی کدهای اندروید ارور  3- میده .

این خطایی هست که  exeption میده .

ErrorAttempt to invoke interface method 'java.util.Iterator java.lang.Iterable.iterator()' on a null object

reference

ممنون میشم راهنماییم بفرمایید.

public class ModuleWebservice {
  public static final int PROTOCOL_EXCEPTION=-1;
  public static final int IO_EXCEPTION=-2;
  public static final int UNKNOWN_EXCEPTION=-3;

  public  interface Listener{
    void onSuccess(String data);
     void onFail(int statuseCode,Exception e);
  }
  private String cacheFileName;
  private String url;
  private ArrayList<NameValuePair> inputArguments;
  private Listener listener;
  private boolean enableCatch;
  private String cacheDir;
  private long cacheExpirTime;
  private int connectionTimeOut;
  private int socketTimeout;


  public ModuleWebservice url(String url){
    this.url=url;
    return  this;
  }

  public ModuleWebservice inputArguments(ArrayList<NameValuePair> value){
    inputArguments=value;
    return  this;
  }

  public ModuleWebservice listener(Listener value){
    listener=value;
    return  this;
  }
  public ModuleWebservice cacheDir(String value){
    cacheDir=value;
    return  this;
  }
  public ModuleWebservice enableCatch(boolean value){
    enableCatch=value;
    return  this;
  }
  public ModuleWebservice cacheExpirTime(long value){
    cacheExpirTime=value;
    return  this;
  }
  public ModuleWebservice socketTimeout(int value){
    socketTimeout=value;
    return  this;
  }
  public ModuleWebservice connectionTimeOut(int value){
    connectionTimeOut=value;
    return  this;
  }
  public void read (){
    String data=null;
    if(enableCatch){
      cacheFileName=creatCacheFileName();
      data=readFromCache();
    }
    if(data==null){
      readFromNet();
    }else{
      final String finalData = data;
      G.handler.post( new Runnable() {
        @Override
        public void run() {
          try {
            listener.onSuccess( finalData );
            return;
          }catch (Exception e){};

        }
      });
    }
  }


  public void readFromNet(){
    Thread thread= new Thread( new Runnable() {
      @Override
      public void run() {
        try{
          HttpParams params=new BasicHttpParams();
          HttpConnectionParams.setConnectionTimeout(params,connectionTimeOut);
          HttpConnectionParams.setSoTimeout(params,socketTimeout);
          HttpClient client=new DefaultHttpClient(params);
          HttpPost request=new HttpPost(url);
          request.setEntity(new UrlEncodedFormEntity(inputArguments));
          HttpResponse httpResponse=client.execute(request);
          final String data=streamToString(httpResponse.getEntity().getContent());
          if(enableCatch){
            saveToCatch( System.currentTimeMillis(),data);
          }
          if(listener!=null){
            G.handler.post( new Runnable() {
              @Override
              public void run() {
                try {
                  listener.onSuccess( data );
                  return;
                }catch (Exception e){};

              }
            });

          }

        }
        catch(ClientProtocolException e){
          if(listener!=null){
            listener.onFail(PROTOCOL_EXCEPTION,e);
          }
        }
        catch (IOException e){
          if(listener!=null){
            listener.onFail(IO_EXCEPTION,e);
          }
        }
        catch (Exception e){
          if(listener!=null){
            listener.onFail(UNKNOWN_EXCEPTION,e);

          }

        }
      }
    });
        thread.start();
  }
  private String creatCacheFileName() {
    String output=url;
    for(NameValuePair input:inputArguments){
      output+=";"+input.getName()+":"+input.getValue();
    }
    String sha1=sha1(output);
    return sha1+".dat";
  }
  final private static char[] hexArray="0123456789ABCDEF".toCharArray();

  private String bytesToHex(byte[] bytes ){
    char[]hexChars=new  char[bytes.length*2];
    for(int j=0;j<bytes.length;j++){
      int v=bytes[j]&0xFF;
      hexChars[j*2]=hexArray[v>>>4];
      hexChars[j*2+1]=hexArray[v&0x0F];
    }
    return new String(hexChars);
  }
  private String sha1(String toHash){
    String hash=null;
    try{
      MessageDigest digest= MessageDigest.getInstance("SHA-1");
      byte[] bytes=toHash.getBytes("UTF-8");
      digest.update(bytes,0,bytes.length);
      bytes=digest.digest();
      hash=bytesToHex(bytes);
    }
    catch (NoSuchAlgorithmException e){
      e.printStackTrace();
    }
    catch (UnsupportedEncodingException e){
      e.printStackTrace();
    }
    return hash;
  }

  private String streamToString(InputStream inputStream){
    BufferedReader bufferedReader=new BufferedReader(new InputStreamReader(inputStream));
    StringBuilder stringBuffer=new StringBuilder();
    String line =null;
    try{
      while((line=bufferedReader.readLine())!=null){
        stringBuffer.append((line+"\n"));
      }

    }catch (IOException e){
      e.printStackTrace();
    }finally {
      try{
        inputStream.close();
      }
      catch(IOException e){
        e.printStackTrace();
      }
    }
    return  stringBuffer.toString();

  }
  private void saveToCatch(long when ,String data){
    ObjectOutputStream outputStream=null;
    try{
      outputStream=new ObjectOutputStream(new FileOutputStream(cacheDir+"/"+cacheFileName));
      outputStream.writeLong(when);
        outputStream.writeInt(data.length());
      outputStream.write(data.getBytes());

    }catch(StreamCorruptedException e){
      e.printStackTrace();
    }catch (FileNotFoundException e){
      e.printStackTrace();}
    catch (IOException e){
      e.printStackTrace();
    }finally{
      if(outputStream!=null){
        try{
          outputStream.flush();
        }catch (IOException e){
          e.printStackTrace();

        }
        try{
          outputStream.close();
        }catch (IOException e){
          e.printStackTrace();
        }
      }
      }
    }

  private String readFromCache() {
    ObjectInputStream inputStream=null;
    try{
      inputStream=new ObjectInputStream(new FileInputStream(cacheDir+"/"+cacheFileName));
      long when=inputStream.readLong();
      long now= System.currentTimeMillis();
      if(now-when>cacheExpirTime*1000){
        new File(cacheDir+"/catch.dat").delete();
        return null;
      }
      int  bytesLenth=inputStream.readInt();
      byte[] buffer=new byte[bytesLenth];
      inputStream.read(buffer,0,bytesLenth);
      String output=new String(buffer);
      return output;
    }
    catch(StreamCorruptedException e)
    {
      e.printStackTrace();
    }
    catch (FileNotFoundException e)
    {
      e.printStackTrace();
    }
    catch (IOException e){
      e.printStackTrace();
    }finally {
      try{
        if(inputStream!=null){
          inputStream.close();
        }

      }
      catch (IOException e){
        e.printStackTrace();
      }
    }
    return  null;

  }




}

webservice.url("www.myweb.ir/android/readCategory")
  .listener( listener)
  .read();