Question

I’m trying to get response from servlet and display it on emulator. Able to get response but when I’m trying to display response on screen, setText is throwing null pointer exception. Unable to figure out the cause. I’m pretty new to android, kindly help me.

package com.example.httptest;

import java.io.IOException;
import java.io.UnsupportedEncodingException;

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.util.EntityUtils;

import com.demo.parser.XmlParser;

import android.os.AsyncTask;
import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;
import android.view.View;
import android.widget.EditText;
import android.widget.TextView;

public class MainActivity extends Activity {

    public static final String url = "http://192.168.3.140:8080/HttpServlet/TestServlet";
    //public static final String url = "http://192.168.3.228/capture/employeeList.xml";
    String output = null;
    TextView outpuText;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.activity_main, menu);
        return true;
    }

    public void invokeServlet(View view){
        AsyncTest test = new AsyncTest();
        System.out.println("URL--------------"+url);
        setContentView(R.layout.activity_main);
        test.execute(new String[] { url });
    }

    private class AsyncTest extends AsyncTask<String, Void, String>{

        @Override
        protected String doInBackground(String... urls) {
            // TODO Auto-generated method stub
            String output = null;

            for(String url :urls){
                System.out.println("url1 "+url);
                output = getOutputFromUrl(url);
                System.out.println("output----------"+output);

                /*EditText text = (EditText) findViewById(R.id.output);

                 text.setText(output);

                */

            }

            return output;
        }

         private String getOutputFromUrl(String url) {
             System.out.println("in hereeeeeeeeeee");

                try {
                    DefaultHttpClient httpClient = new DefaultHttpClient();
                    HttpGet httpGet = new HttpGet(url);

                    HttpResponse httpResponse = httpClient.execute(httpGet);
                    HttpEntity httpEntity = httpResponse.getEntity();
                    output = EntityUtils.toString(httpEntity);
                    System.out.println("output1 "+output);
                   // XmlParser.XMLfromString(output);
                } catch (UnsupportedEncodingException e) {
                    e.printStackTrace();
                } catch (ClientProtocolException e) {
                    e.printStackTrace();
                } catch (IOException e) {
                    e.printStackTrace();
                }
                return output;
            }


         protected void onPostExecute(String output){

             setContentView(R.layout.activity_main);
             outpuText.setText(output);


             setContentView(outpuText);
         }



    }

}

Answer 1

Issue resolved by adding following step in onCreate method,

outpuText = new TextView(this);

Thanks for your time guys!!