Changing background of single row gridview in android

I am currently developing an Android application that should display a bookshelf where each line contains a maximum of 3 images. I use gridview for this. But I am stuck at one point where I cannot change the background of the whole row in gridview. can anyone tell me how to do this?

Adapter used for gridview

private class SampleGridAdapter extends BaseAdapter{

    private Context context;
    private int[] images = {"R.drawable.img1","R.drawable.img2","R.drawable.img3","R.drawable.img4","R.drawable.img5","R.drawable.img6","R.drawable.img7"};
    public SampleGridAdapter(Context context) {
        super();
        this.context = context;

    }
    @Override
    public int getCount() {
        // TODO Auto-generated method stub
        return images.length;
    }
    @Override
    public Object getItem(int arg0) {
        // TODO Auto-generated method stub
        return null;
    }

    @Override
    public long getItemId(int arg0) {
        // TODO Auto-generated method stub
        return 0;
    }

    @Override
    public View getView(int arg0, View arg1, ViewGroup arg2) {
        // TODO Auto-generated method stub

        View v = null;
        ImageView coverImageView;

        LayoutInflater inflater = (LayoutInflater)context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);

            v = inflater.inflate(R.layout.bookgrid, null);
            coverImageView = (ImageView) v.findViewById(R.id.coverImageView);   
            coverImageView.setImageResource(images[position]);


            coverImageView.setScaleType(ImageView.ScaleType.FIT_XY);

        return v;
    }
}

bookgrid.xml

<?xml version="1.0" encoding="utf-8"?>
 <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="@drawable/shelfimage" >

<ImageView
    android:id="@+id/coverImageView"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignParentLeft="true"
    android:paddingBottom="0dp"
    android:paddingLeft="25dp"
    android:paddingTop="6dp"
    android:src="@drawable/ic_launcher" />
 </RelativeLayout>

I set the number of columns to 3 in the gridview declaration. Here I set the background in the xml file as android: background = "@ drawable / shelfimage". but he sets this background for each element separately ... I want to set one image as a background for each line (having 3 elements) ....