Updare Activity UI from Service once processing done-- Using Broadcast Receiver

Service Implementation:

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.URL;

import android.app.Activity;
import android.app.IntentService;
import android.content.Intent;
import android.net.Uri;
import android.os.Bundle;
import android.os.Environment;
import android.os.Message;
import android.os.Messenger;
import android.util.Log;

public class DownloadService extends IntentService {

    private int result = Activity.RESULT_CANCELED;
    public static final String URL = "urlpath";
    public static final String FILENAME = "filename";
    public static final String FILEPATH = "filepath";
    public static final String RESULT = "result";
    public static final String NOTIFICATION = "com.vogella.android.service.receiver";

    public DownloadService() {
        super("DownloadService");
    }

    // will be called asynchronously by Android
    @Override
    protected void onHandleIntent(Intent intent) {
        String urlPath = intent.getStringExtra(URL);
        String fileName = intent.getStringExtra(FILENAME);
        File output = new File(Environment.getExternalStorageDirectory(),
                fileName);
        if (output.exists()) {
            output.delete();
        }

        InputStream stream = null;
        FileOutputStream fos = null;
        try {

            URL url = new URL(urlPath);
            stream = url.openConnection().getInputStream();
            InputStreamReader reader = new InputStreamReader(stream);
            fos = new FileOutputStream(output.getPath());
            int next = -1;
            while ((next = reader.read()) != -1) {
                fos.write(next);
            }
            // successfully finished
            result = Activity.RESULT_OK;

        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            if (stream != null) {
                try {
                    stream.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if (fos != null) {
                try {
                    fos.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
        publishResults(output.getAbsolutePath(), result);
    }

    private void publishResults(String outputPath, int result) {
        Intent intent = new Intent(NOTIFICATION);
        intent.putExtra(FILEPATH, outputPath);
        intent.putExtra(RESULT, result);
        sendBroadcast(intent);
    }
}

Activity Implementation:

import android.app.Activity;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.os.Bundle;
import android.view.View;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends Activity {

    private TextView textView;
    private BroadcastReceiver receiver = new BroadcastReceiver() {

        @Override
        public void onReceive(Context context, Intent intent) {
            Bundle bundle = intent.getExtras();
            if (bundle != null) {
                String string = bundle.getString(DownloadService.FILEPATH);
                int resultCode = bundle.getInt(DownloadService.RESULT);
                if (resultCode == RESULT_OK) {
                    Toast.makeText(MainActivity.this,
                            "Download complete. Download URI: " + string,
                            Toast.LENGTH_LONG).show();
                    textView.setText("Download done");
                } else {
                    Toast.makeText(MainActivity.this, "Download failed",
                            Toast.LENGTH_LONG).show();
                    textView.setText("Download failed");
                }
            }
        }
    };

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        textView = (TextView) findViewById(R.id.status);


    }

    @Override
    protected void onResume() {
        super.onResume();
        registerReceiver(receiver, new IntentFilter(
                DownloadService.NOTIFICATION));
    }
    @Override
    protected void onPause() {
        super.onPause();
        unregisterReceiver(receiver);
    }

    public void onClick(View view) {

        Intent intent = new Intent(this, DownloadService.class);
        // add infos for the service which file to download and where to store
        intent.putExtra(DownloadService.FILENAME, "index.html");
        intent.putExtra(DownloadService.URL,
                "http://www.vogella.com/index.html");
        startService(intent);
        textView.setText("Service started");
    }
}