httpclient is unable to execute the httpget object

Question

I am learning android. I started working on networking with android. The problem i m facing is that under the try statement the httpclient.execute(request) line is not working. Instead the catch clause is executed every time. I have searched for quite a long time but i m not getting answers regarding the problem. i'll be pleased to get any kind of help from ur side.

Here is the main activity

package com.example.androidaspect;

import android.app.Activity;
import android.content.Context;
import android.os.Bundle;
import android.widget.TextView;

public class MainActivity extends Activity {

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

        Context context = getApplicationContext();
        String url = "http://www.google.com";
        TextView tv = (TextView) findViewById(R.id.tvres);

        AsyncTaskRunner runner = new AsyncTaskRunner();
        runner.execute(url, context, tv);

    }

}

Here is the Asynctaskrunner

package com.example.androidaspect;

import java.io.BufferedReader;
import java.io.InputStreamReader;

import org.apache.http.HttpResponse;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.DefaultHttpClient;

import android.content.Context;
import android.os.AsyncTask;
import android.widget.TextView;
import android.widget.Toast;

public class AsyncTaskRunner extends AsyncTask<String, String, String>{

    Context context;
    TextView tv;
    String url;
    String result="";

    public void execute(String url, Context context, TextView tv) {
        // TODO Auto-generated method stub
        this.tv= tv;
        this.context = context;
        this.url = url;
    }

    @Override
    protected String doInBackground(String... params) {
        // TODO Auto-generated method stub
        try{
            publishProgress("Loading");
            HttpClient hc = new DefaultHttpClient();
            HttpGet request = new HttpGet(url);
            HttpResponse res = hc.execute(request);

            BufferedReader rd = new BufferedReader(new InputStreamReader(res.getEntity().getContent()));
            String line="";
            while((line=rd.readLine())!=null){
                result.concat(line);
            }

        }catch(Exception e){
            e.printStackTrace();
        }
        return result;
    }

    @Override
    protected void onPostExecute(String result) {
        // TODO Auto-generated method stub
        tv.setText(result);
    }

    @Override
    protected void onProgressUpdate(String... values) {
        // TODO Auto-generated method stub
        Toast.makeText(context, values[0], Toast.LENGTH_SHORT).show();
    }

}

I have added the internet permission. i have a textview in my xml which is getting the response from the website. but when i run the app on the emulator, it runs but the textview does not load the data.

Answer 1

As i mentioned in the comment use AsyncTask.

Quoting docs

The exception that is thrown when an application attempts to perform a networking operation on its main thread.

This is only thrown for applications targeting the Honeycomb SDK or higher. Applications targeting earlier SDK versions are allowed to do networking on their main event loop threads, but it's heavily discouraged

http://developer.android.com/reference/android/os/AsyncTask.html

public class MainActivity extends Activity {

    TextView tv;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.tvres);
        tv = (TextView) findViewById(R.id.textView1);
        new TheTask().execute();

    }
    class TheTask extends AsyncTask<Void,Void,String>
    {

        @Override
        protected String doInBackground(Void... arg0) {
            // TODO Auto-generated method stub
             String response=null; 
             try {

                    HttpClient hc = new DefaultHttpClient();
                    HttpGet hg = new HttpGet("http://www.google.com");
                    HttpResponse res = hc.execute(hg);
                    HttpEntity entity = res.getEntity();
                    response = EntityUtils.toString(entity);

                } catch (Exception e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
            return response;
        }

        @Override
        protected void onPostExecute(String result) {
            // TODO Auto-generated method stub
            super.onPostExecute(result);
            tv.setText(result);
        }

    }

You have AsyncTask as a inner class.

 class TheTask extends AsyncTask<Void,Void,String>

You do not pass anything to doInbackground .So the first arg type is Void. The second arg is also Void coz you do not have a progress indicator. The third is the type of the result of the background computation. So its string since we have return response; which is string.

Now doInbackground is invoked on the background thread. SO do your background computation there.

onPostExecute is invoked on the ui thread. So update ui there.

Edit:

Your way

public class MainActivity extends Activity {

    TextView tv;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        String url = "http://www.google.com";
         tv = (TextView) findViewById(R.id.tvres);
        AsyncTaskRunner runner = new AsyncTaskRunner(url,this,tv);
        runner.execute();


    }
    }

Then

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

    Context context;
    TextView tv;
    String url;
    String result="";

    public  AsyncTaskRunner(String url, Context context, TextView tv) {
        // TODO Auto-generated method stub
        this.tv= tv;
        this.context = context;
        this.url = url;
    }

    @Override
    protected String doInBackground(Void... params) {
        // TODO Auto-generated method stub

            publishProgress("Loading");
            String response=null; 
            try {

                   HttpClient hc = new DefaultHttpClient();
                   HttpGet hg = new HttpGet(url);
                   HttpResponse res = hc.execute(hg);
                   HttpEntity entity = res.getEntity();
                   response = EntityUtils.toString(entity);

        }catch(Exception e){
            e.printStackTrace();
        }
          return response;
    }

    @Override
    protected void onPostExecute(String result) {
        // TODO Auto-generated method stub
        tv.setText(result);
    }

    @Override
    protected void onProgressUpdate(String... values) {
        // TODO Auto-generated method stub
        Toast.makeText(context, values[0], Toast.LENGTH_SHORT).show();
    }

}

Answer 2

You need to use AsyncTask<> or IntentService to handle HttpQueries