问如何在InfoWindow上将drawable作为背景？

<RelativeLayout 
        xmlns:android="http://schemas.android.com/apk/res/android"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:background="@drawable/bg_infowindow" >
    <LinearLayout
            android:id="@+id/text_box"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:orientation="vertical" >
        <TextView 
            style="@style/TexTitle"
            android:id="@+id/title"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content" />
    <TextView 
            style="@style/TextDistance"
            android:id="@+id/distance"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content" />
    </LinearLayout>
</RelativeLayout>

public class MapInfoWindowAdapter implements InfoWindowAdapter{

    private LayoutInflater inflater;
    private Context context;

    public MapInfoWindowAdapter(Context context){
        inflater = (LayoutInflater) context.getSystemService( Context.LAYOUT_INFLATER_SERVICE );
        this.context = context;
    }

    @Override
    public View getInfoContents(Marker marker) {

        // Getting view from the layout file
        View v = inflater.inflate(R.layout.map_popup, null);

        TextView title = (TextView) v.findViewById(R.id.title);
        title.setText(marker.getTitle());

        TextView address = (TextView) v.findViewById(R.id.distance);
        address.setText(marker.getSnippet());

        return v;
    }

    @Override
    public View getInfoWindow(Marker arg0) {
        // TODO Auto-generated method stub
        return null;
    }

}