访问.net wcf服务时出现空指针异常

Question

I am new to Android and i am trying to access wcf service from android its giving null pointer exception, here is my .net wcf service IUserService

[ServiceContract]
public interface IUserService
{       [OperationContract]
    [WebInvoke(Method="GET",ResponseFormat = WebMessageFormat.Json,UriTemplate =    "GetName")]
    string GetName();      
}

here is my UserService

public class UserService : IUserService
{
public string GetName()
    {
        return "Hello ! ";
    }
}

here is my xml

 <service name="Lera.Template.Services.WCF.UserService">
    <endpoint address="" binding="webHttpBinding" contract="Lera.Template.Services.WCF.IUserService" 
              behaviorConfiguration="httpBehavior">
      <identity>
        <dns value="localhost" />
      </identity>
    </endpoint>
    <endpoint address="mex" binding="mexHttpBinding" contract="IMetadataExchange" />
    <host>
      <baseAddresses>
        <add baseAddress="http://localhost:8888/Lera.Template.Services.WCF/UserService/" />
      </baseAddresses>
    </host>
  </service>    

I am using eclipse here is my main activity

public class MainActivity extends Activity {

 private String values ="";
Button btn;
  TextView tv;
  private static String url = "http://192.168.12.146:8888/Lera.Template.Services.WCF/UserService/GetName";
  private static final String StringVal = "StringValue";
 @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);       


        JSONParser jParser = new JSONParser();

        // getting JSON string from URL
        JSONObject json = jParser.getJSONFromUrl(url); 
        try {

           String temp = json.getString(StringVal);          
            Toast toast = Toast.makeText(this ,temp , Toast.LENGTH_SHORT);
            toast.show();        

        } 

        catch (JSONException e) {
            e.printStackTrace();
        }

        catch (Exception ex) {
            Log.e("final:", ex.toString());
        }

 }
}

I am using json parser class public class JSONParser {

static InputStream is = null;
static JSONObject jObj = null;
static String json = "";

// constructor
public JSONParser() {

}

public JSONObject getJSONFromUrl(String url) {

    // Making HTTP request
    try {
        // defaultHttpClient
        DefaultHttpClient httpClient = new DefaultHttpClient();
        HttpGet httpget = new HttpGet(url);

        HttpResponse httpResponse = httpClient.execute(httpget);
        HttpEntity httpEntity = httpResponse.getEntity();
        is = httpEntity.getContent();           

    } catch (UnsupportedEncodingException e) {
        e.printStackTrace();
    } catch (ClientProtocolException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
        Log.e("connection" , e.toString());
    }

    try {
        BufferedReader reader = new BufferedReader(new InputStreamReader(is, "iso-8859-1"), 8);
        StringBuilder sb = new StringBuilder();
        String line = null;
        while ((line = reader.readLine()) != null) {
            sb.append(line + "\n");
        }
        is.close();
        json = sb.toString();//here json type is string 
    } catch (Exception e) {
        Log.e("Buffer Error", "Error converting result " + e.toString());
    }

    // try parse the string to a JSON object
    try {
        jObj = new JSONObject(json);
    } catch (JSONException e) {
        Log.e("JSON Parser", "Error parsing data " + e.toString());
    }

    // return JSON String
    return jObj;

}
}

Wcf Service is working fine on browser but when i try to access from my android application its giving null pointer exception

the line that is giving null pointer exception is

HttpResponse httpResponse = httpClient.execute(httpget); 

Please help me in solving this, I have tried all the things which are available on net but still unable to overcome this.

As AS mention I updated my main activity class here is my main activity with Async calls but the Exception is connection to url refused

public class MainActivity extends Activity implements OnClickListener {

 private String values ="";
Button btn;
  TextView tv;
  String uri = "http://192.168.0.144:8888/Lera.Template.Services.WCF/UserService/GetName";

 @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        btn = (Button)this.findViewById(R.id.btnAccess);
        tv = (TextView)this.findViewById(R.id.tvAccess);
        btn.setOnClickListener(this);
    }

    @Override
    public void onClick(View arg0) {
        try
        {
        AsyncTaskExample task = new AsyncTaskExample(this);
        task.execute("");
        String  test = values;
        tv.setText(values);
        } catch(Exception e)
        {
           Log.e("Click Exception: ", e.getMessage());   
        }

    }

    public class AsyncTaskExample extends AsyncTask<String, Void,String>
    {
        private String Result="";
        //private final static String SERVICE_URI = "http://10.0.2.2:8889";
        private final static String SERVICE_URI = "http://192.168.12.146:8888/Lera.Template.Services.WCF/UserService";
        private MainActivity host;
        public AsyncTaskExample(MainActivity host)
        {
            this.host = host;
        }

        public String GetSEssion(String URL)
        {
          boolean isValid = true;
          if(isValid)
          {

              HttpClient client = new DefaultHttpClient();
              //http://192.168.0.144:8888/Lera.Template.Services.WCF/UserService/
             // HttpPost post = new HttpPost(uri);
              HttpGet httpget = new HttpGet(uri);
            httpget.setHeader("Accept", "application/json");
            httpget.setHeader("Content-type", "application/json; charset=utf-8");

              try
              {      
                HttpResponse response = client.execute(httpget) ;
                BufferedReader rd = new BufferedReader(new InputStreamReader(response.getEntity().getContent()));
                String line ="";
                while((line = rd.readLine()) != null)
                {
                    System.out.println(line);
                }
              }catch(Exception e)
              {
                  Log.e("Error:", e.getMessage());

              }
         }
          return Result;
        }

        @Override
        protected String doInBackground(String... arg0) {
            android.os.Debug.waitForDebugger();
            String t = GetSEssion(SERVICE_URI);
            return t;
        }

        @Override
        protected void onPostExecute(String result) {
        //  host.values = Result;
            super.onPostExecute(result);
        }
        @Override
        protected void onPreExecute() {
            // TODO Auto-generated method stub
            super.onPreExecute();
        }

        @Override
        protected void onCancelled() {
            // TODO Auto-generated method stub
            super.onCancelled();
        }
    }

}

Any help would be appriciated. Thankyou.

Answer 1

Otherwise i can give you the following advice : There's no need for a whole class (JSONParser) for just one method. Just add the method and variables to MainActivity.

EDIT: Actually are you using an android device or an emulator? If you're using an emulator you can access your host computer by using 10.0.2.2 . You would change your url to http://10.0.2.2.146:8888/Lera.Template.Services.WCF/UserService/GetName