Xamarin.Forms で上下等間隔2分割のレイアウトを行うサンプル

LayoutTestPage.xaml

<?xml version="1.0" encoding="utf-8"?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms" 
  xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml" 
  xmlns:local="clr-namespace:SepTest" x:Class="LayoutTest.LayoutTestPage">
  <ContentPage.Content>
    <!--Grid を使う方法-->
<!--    
    <Grid HorizontalOptions="Fill" VerticalOptions="Fill">
      <Grid.RowDefinitions>
        <RowDefinition Height="*" />
        <RowDefinition Height="*" />
      </Grid.RowDefinitions>
      <BoxView Grid.Row="0" BackgroundColor="Aqua" />
      <BoxView Grid.Row="1" BackgroundColor="Lime" />
    </Grid>
-->  

    <!--StackLayout を使う方法-->
<!--  
    <StackLayout VerticalOptions="Fill" HorizontalOptions="Fill">
      <BoxView BackgroundColor="Aqua" VerticalOptions="FillAndExpand" />
      <BoxView BackgroundColor="Lime" VerticalOptions="FillAndExpand" />
    </StackLayout>
-->
    <!--RelativeLayout を使う方法-->
    <RelativeLayout VerticalOptions="Fill" HorizontalOptions="Fill">
      <BoxView BackgroundColor="Aqua" 
        RelativeLayout.WidthConstraint
          = "{ConstraintExpression Type=RelativeToParent,Property=Width, Factor=1.0}"
        RelativeLayout.HeightConstraint
          = "{ConstraintExpression Type=RelativeToParent,Property=Height, Factor=0.5}"
      />
      <BoxView BackgroundColor="Lime" 
        RelativeLayout.YConstraint
          = "{ConstraintExpression Type=RelativeToParent,Property=Height, Factor=0.5}"
        RelativeLayout.WidthConstraint
          = "{ConstraintExpression Type=RelativeToParent,Property=Width, Factor=1.0}"
        RelativeLayout.HeightConstraint
          = "{ConstraintExpression Type=RelativeToParent,Property=Height, Factor=0.5}"
      />
    </RelativeLayout>
  </ContentPage.Content>
</ContentPage>