android webview layout to take remaining space

I want to create, what seems to be a simple layout, but I am having a few problems with it. The layout consists of a header, body which is a webview, and a footer banner on bottom as seen on the attached sketch. I need the webview to take all the remaining space between the header and footer. I have tried this: ``` <?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:orientation="vertical" android:background="@drawable/back" android:layout_width="fill_parent" android:layout_height="fill_parent"> <ImageView android:id="@+id/banner" android:layout_height="wrap_content" android:layout_width="wrap_content" android:src="@drawable/banner" /> <WebView android:id="@+id/webview" android:layout_width="fill_parent" android:layout_height="fill_parent" android:background="@drawable/bck" android:layout_weight="2" android:layout_gravity="center"/> <RelativeLayout android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_weight="4"> <com.mobclix.android.sdk.MobclixMMABannerXLAdView android:id="@+id/banner_adview" android:layout_width="320dip" android:layout_height="50dip" android:layout_gravity="center" android:layout_alignParentBottom="true" /> </RelativeLayout> ```