Scrollview with ScrollView VerticalOptions="Center" not growing to fit contents on iOS

krime81 commented 4 months ago

Description

When a ScrollView has dynamic contents ( in this example, a view that is growing in size, or made visible ) it doesnt grow to fit its contents on iOS, but it does on Android

Steps to Reproduce

Create a xaml file with following contents `<?xml version="1.0" encoding="utf-8" ?> <ContentPage xmlns="http://schemas.microsoft.com/dotnet/2021/maui" xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml" x:Class="mauiscrollissue.MainPage">

<ScrollView VerticalOptions="Center" Background="Red" Padding="10">
    <VerticalStackLayout BackgroundColor="Aqua"
        Padding="30,0"
        Spacing="25">
        <Frame x:Name="hiddenAtFirst" BackgroundColor="Green" HeightRequest="200" IsVisible="false"/>
        <Frame BackgroundColor="Blue" HeightRequest="200" IsVisible="true"/>

        <Button
            x:Name="MakeVisibleButton"
            Text="Click me to grow" 
            Clicked="OnMakeVisibleButtonClicked"
            HorizontalOptions="Fill" />
    </VerticalStackLayout>
</ScrollView>

`

with codebehind : `namespace mauiscrollissue;

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

private void OnMakeVisibleButtonClicked(object sender, EventArgs e)
{
    hiddenAtFirst.IsVisible = true;
    hiddenAtFirst.HeightRequest += 100;
}

} `

On tapping the button, -on Android the scrollview grows until it reaches the max height, and then shows the scrolling behavior -on iOS the scrollview doesnt grow and immediately shows scrolling behavior

Link to public reproduction project repository

https://github.com/krime81/mauiscrollissue

Version with bug

9.0.0-preview.1.9973

Is this a regression from previous behavior?

Not sure, did not test other versions

Last version that worked well

Unknown/Other

Affected platforms

iOS

Affected platform versions

No response

Did you find any workaround?

add this handler : ` Microsoft.Maui.Handlers.ScrollViewHandler.Mapper.AppendToMapping(nameof(IScrollView.ContentSize), (h, v) => { var contentSize = h.VirtualView.ContentSize;

            if (contentSize.IsZero)
                return;

            UIKit.UIScrollView uiScrollView = h.PlatformView;
            var container = uiScrollView.Subviews.FirstOrDefault(x => x.Tag == 0x845fed);           

            if (container != null && container.Bounds.Height != contentSize.Height)
            {
                container.Bounds = new CoreGraphics.CGRect(
                    container.Bounds.X,
                    container.Bounds.Y, 
                    contentSize.Width, 
                    contentSize.Height);

                (h.VirtualView as IView).InvalidateMeasure();
            }
        });
            `

note that this might affect other instances of the scrollview in your projects

Relevant log output

No response

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