Absolute layout working inconsistently across platforms

Description

Using an AbsoluteLayout to position a floating button behaves inconsistently between UWP, iOS and Android.

Steps to Reproduce

Please see the attached zip for a reproduction.

1. Create a new blank Xamarin Forms project
2. Use the following XAML code

<?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:AbsoluteLayoutBugs"
             x:Class="AbsoluteLayoutBugs.MainPage">

    <StackLayout>

        <ListView>

            <ListView.ItemsSource>
                <x:Array Type="{x:Type x:String}">
                    <x:String>Item 1</x:String>
                    <x:String>Item 2</x:String>
                    <x:String>Item 3</x:String>
                    <x:String>Item 4</x:String>
                    <x:String>Item 5</x:String>
                    <x:String>Item 6</x:String>
                    <x:String>Item 7</x:String>
                    <x:String>Item 8</x:String>
                    <x:String>Item 9</x:String>
                    <x:String>Item 10</x:String>
                    <x:String>Item 11</x:String>
                    <x:String>Item 12</x:String>
                    <x:String>Item 13</x:String>
                    <x:String>Item 14</x:String>
                    <x:String>Item 15</x:String>
                    <x:String>Item 16</x:String>
                    <x:String>Item 17</x:String>
                    <x:String>Item 18</x:String>
                    <x:String>Item 19</x:String>
                    <x:String>Item 20</x:String>
                </x:Array>
            </ListView.ItemsSource>
            
        </ListView>

        <AbsoluteLayout HeightRequest="1" MinimumHeightRequest="1">
            <Button Text="?" BackgroundColor="Blue" HeightRequest="50" WidthRequest="50" 
                        CornerRadius="25" x:Name="Button" AbsoluteLayout.LayoutBounds="0,-100,50,50" />

        </AbsoluteLayout>

    </StackLayout>

</ContentPage>

3. Use the following code behind:

	public partial class MainPage : ContentPage
	{
		public MainPage()
		{
			InitializeComponent();

                        Button.Clicked += async (s, e) =>
                        {
                             await DisplayAlert("Clicked", "Clicked", "OK");
                        };
		}
	}

Expected Behavior

The floating button should be positioned over the listview and clickable.

Actual Behavior

UWP Working as expected

iOS Positioned as expected, Clicked event not firing

Android Not positioned as expected. Unknown whether Clicked event is fired.

Basic Information

• Version with issue: 3.1.0.697729
• Last known good version: N/A
• IDE: VS 2017 15.7.4
• Platform Target Frameworks:
  • iOS: 11.4
  • Android: 7.1
  • UWP: 16299
• Android Support Library Version: N/A
• Nuget Packages: N/A
• Affected Devices: Android, iOS

Screenshots

Reproduction Link

Please see attached zip. AbsoluteLayoutBugs.zip