Dynamic HeightRequest not working correctly in xamarin forms

Question

In my XAML I have this StackLayout:

Answer 1

We can use HeightRequest, but keep in mind that it is just a request. If Xamarin.Forms doesn't have enough pixels/points to fulfill the request, it will make a best effort.

After changing HeightRequest, we will need to tell Xamarin.Forms to redraw the StackLayout and the ContentPage by calling ForceLayout();

public partial class MyContentPage : ContentPage
{
    ...

    void ResizeFooterWrapper(double heightRequest)
    {
        // Ensure resizing is marshaled to the UI Thread
        Device.BeginInvokeOnMainThread(() => 
        {
            FooterWrapper.HeightRequest = heightRequest;
            FooterWrapper.ForceLayout();
            this.ForceLayout();
        });
    }
}

Sample App

Link to Sample App: https://github.com/brminnick/DynamicStackLayoutSize/

using System;

using Xamarin.Forms;

namespace DynamicStackLayoutSize
{
    public class App : Application
    {
        public App() => MainPage = new MyPage();
    }

    class MyPage : ContentPage
    {
        readonly StackLayout _adjustableStackLayout;

        public MyPage()
        {
            _adjustableStackLayout = new StackLayout
            {
                HorizontalOptions = LayoutOptions.Center,
                VerticalOptions = LayoutOptions.Center,
                BackgroundColor = Color.Green,
                Children = {
                    new Label{ Text = "Hello" },
                    new Label{ Text = "World" }
                }
            };

            var resizeButton = new Button { Text = "Resize" };
            resizeButton.Clicked += (s, e) =>
            {
                if (_adjustableStackLayout.HeightRequest == 196)
                    ResizeStackLayout(-1);
                else
                    ResizeStackLayout(196);
            };

            Content = new StackLayout
            {
                HorizontalOptions = LayoutOptions.Center,
                VerticalOptions = LayoutOptions.Center,
                BackgroundColor = Color.Red,
                Children ={
                    _adjustableStackLayout,
                    resizeButton
                }
            };
        }

        void ResizeStackLayout(double heightRequest)
        {
            Device.BeginInvokeOnMainThread(() =>
            {
                _adjustableStackLayout.HeightRequest = heightRequest;
                _adjustableStackLayout.ForceLayout();
                this.ForceLayout();
            });
        }
    }
}

Sample App Gif