Android - Ayuda con ImageButton

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

    android:orientation="vertical"

    android:layout_width="fill_parent"

    android:layout_height="fill_parent">

 <ImageView android:id="@+id/image_view"

    android:layout_width="wrap_content"

    android:layout_height="wrap_content" />

</LinearLayout>

public class Main extends Activity {

    private ImageView imageView;

    private Bitmap loadedImage;

    private String imageHttpAddress = "http://jonsegador.com/wp-content/apezz.png";

    @Override

    public void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.main);

        imageView = (ImageView) findViewById(R.id.image_view);

        downloadFile(imageHttpAddress);

    }

    void downloadFile(String imageHttpAddress) {

        URL imageUrl = null;

        try {

            imageUrl = new URL(imageHttpAddress);

            HttpURLConnection conn = (HttpURLConnection) imageUrl.openConnection();

            conn.connect();

            loadedImage = BitmapFactory.decodeStream(conn.getInputStream());

            imageView.setImageBitmap(loadedImage);

        } catch (IOException e) {

            Toast.makeText(getApplicationContext(), "Error cargando la imagen: "+e.getMessage(), Toast.LENGTH_LONG).show();

            e.printStackTrace();

        }

    }

}