How to make a stacklayout fixed to the bottom of the screen in a scrollview

l have code that has views in a scrolleview.. l want to be able to make the last stacklayout to be fixed in the scrollview such that all other elements can scroll but the stacklayout is fixed. Much like fixed footer in a web page

<?xml version="1.0" encoding="utf-8"?>

<NavigationPage.TitleView >

</NavigationPage.TitleView>  

<CollectionView.ItemsLayout>


Horizontal


</CollectionView.ItemsLayout>
<CollectionView.ItemTemplate>


<Grid.RowDefinitions >


</Grid.RowDefinitions>
<Grid.ColumnDefinitions>

</Grid.ColumnDefinitions>




</CollectionView.ItemTemplate>





<CollectionView.ItemsLayout>


Horizontal


</CollectionView.ItemsLayout>
<CollectionView.ItemTemplate>


<Grid.RowDefinitions >


</Grid.RowDefinitions>
<Grid.ColumnDefinitions>

</Grid.ColumnDefinitions>




</CollectionView.ItemTemplate>

     </StackLayout>   

Any Ideas..