Question

I am getting an issue to run the below code.The code gives no error but not giving the expected output. Any suggestions or solution will be highly appreciated.Thanx in advance.

Here’s my xml file:-

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >

    <Button android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:id="@+id/readWebpage"
            android:text="Load Webpage"
            android:onClick="readWebpage"/>

    <TextView android:layout_width="wrap_content"
              android:layout_height="wrap_content"
              android:id="@+id/textView1"
              android:text="Example Text"
              android:layout_gravity="center_horizontal"/>

</LinearLayout>

and here’s my java file:-

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

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

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

public class LoadWebpageAsyncTask extends Activity {

    TextView tv;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        // TODO Auto-generated method stub
        super.onCreate(savedInstanceState);
        tv = (TextView)findViewById(R.id.textView1);

    }
    public class DownloadWebpageTask extends AsyncTask<String,Void,String>{

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

            String response = "";
            for(String url:urls){
                DefaultHttpClient client = new DefaultHttpClient();
                HttpGet httpGet = new HttpGet(url);
                try{
                    HttpResponse execute = client.execute(httpGet);
                    BufferedReader br = new BufferedReader(new 
                            InputStreamReader(execute.getEntity().getContent()));
                    String s="";
                    while((s = br.readLine()) != null){

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


        @Override
        protected void onPostExecute(String result) {
            // TODO Auto-generated method stub

            tv.setText(result);
        }

    }

        public void readWebpage(View view){ 
            DownloadWebpageTask task = new DownloadWebpageTask();
            task.execute(new String[]{"http://www.google.com"});

            }
}

Answer 1

It looks like you are missing setContentView(R.layout.<...>); (tv will be null) in your onCreate() method and never run your task (so you don’t get NullPointerException when setting text on tv):

@Override
protected void onCreate(Bundle savedInstanceState) {
    // TODO Auto-generated method stub
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);
    tv = (TextView)findViewById(R.id.textView1);
    readWebpage(null); //you never use argument anyway
}

edit riha’s answer is also true, since the way you use it is for (String[] url:urls), not for (String url:urls)