CollectionView ScrollTo not working under android

[Schniefel]

Description

Exactly like described here: #2891

I am not able to manually scroll the CollectionView under android with ".ScrollTo". Simply nothing happens.
It is working under Windows though.
The issue seems to be closed, but what is the fix?
I don't get it.

Steps to Reproduce

No response

Link to public reproduction project repository

No response

Version with bug

9.0.22 SR2.2

Is this a regression from previous behavior?

Not sure, did not test other versions

Last version that worked well

No response

Affected platforms

Android

Affected platform versions

No response

Did you find any workaround?

no

Relevant log output

[similar-issues-ai]

We've found some similar issues:

• [Android] CollectionView ScrollTo methods not working #4110 , similarity score: 86%
• [Android] CollectionView ScrollTo using the index not working #22188 , similarity score: 86%
• CollectionView: ScrollTo does not work [Windows11, Android11/12, iOS not tested] dotnet --version: 6.0.400 #9920 , similarity score: 85%
• [Bug] CollectionView ScrollTo methods not working on Android #2891 , similarity score: 82%

If any of the above are duplicates, please consider closing this issue out and adding additional context in the original issue.

Note: You can give me feedback by 👍 or 👎 this comment.

[Ying-6]

This issue has been verified Visual Studio 17.13 Preview 2.1 (9.0.22 & 9.0.21 & 9.0.0). Can repro this issue on Android platform.

According to the comment of issue #2891, this seems to be due to the stacklayout is having an infinite height. After changing the Layouts, it works well. The changed project is as follows:
MauiApp2891.zip

[Schniefel]

I don't use a single stacklayout in the whole page. My Collectionview is embedded in a Grid.

[Schniefel]

I found out something new. I found out, that I have to ScrollTo index 1 under Android opposed to index 0 under Windows. It works perfectly reproducible, but I have no idea why...

What I wanted to achieve is, to scroll at startup at the beginning of the first element of my collection to hide the header of the CollectionView and make it only visible if the user is scrolling up.

Now I have something like this in the OnAppearing() method of my page:

#if ANDROID
            Dispatcher.Dispatch(() => myCollectionView.ScrollTo(1, position: ScrollToPosition.Start, animate: false));//for whatever reason we have to scroll to position 1 under android
#else
            Dispatcher.Dispatch(() => myCollectionView.ScrollTo(0, position: ScrollToPosition.Start, animate: false));
#endif

Maybe this is related to: #26468 or #25649

[Schniefel]

Any news on this? The latest update of the nuget package Microsoft.Maui.Controls 9.0.30 did not change anything.

[Shalini-Ashokan]

I don't use a single stacklayout in the whole page. My Collectionview is embedded in a Grid.

It will be great, if you can share a sample here. Which will be helpful for replicating the issue.

[Schniefel]

That is pretty easy. Use either the uploaded solution (TestMAUI.zip) directly or create a new solution with the following steps:

1. Create a new MAUI App project using .NET 9
2. Use the following XAML for MainPage.xaml

<?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"
             xmlns:local="clr-namespace:TestMAUI"
             x:Class="TestMAUI.MainPage">

    <Grid>
        <CollectionView x:Name="myCollectionView" x:DataType="local:MyData" Loaded="myCollectionView_Loaded">
            <CollectionView.ItemTemplate>
                <DataTemplate>
                    <Label Text="{Binding Name}"  FontSize="Large"/>
                </DataTemplate>
            </CollectionView.ItemTemplate>
            <CollectionView.Header>
                <Label Text="HEADER" FontSize="Header"/>
            </CollectionView.Header>
        </CollectionView>
    </Grid>

</ContentPage>

3. Use the following code to MainPage.xaml.cs

using System.Collections.ObjectModel;

namespace TestMAUI
{
    public class MyData
    {
        public string Name { get; }

        public MyData(string name)
        {
            Name = name;
        }
    }

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

            //populate data and make sure the list is long enought that it needs to scroll to the first element
            ObservableCollection<MyData> data = new ObservableCollection<MyData>();
            for (int i = 0; i < 100; i++)
            {
                data.Add(new MyData($"Item {i}"));
            }

            myCollectionView.ItemsSource = data;
        }

        private void myCollectionView_Loaded(object sender, EventArgs e)
        {
#if ANDROID
            myCollectionView.ScrollTo(1, position: ScrollToPosition.Start, animate: false);
#else
            myCollectionView.ScrollTo(0, position: ScrollToPosition.Start, animate: false);
#endif
        }
    }

}

4. What I wanted to achieve is that the header of the CollectionView is not visible at startup and the user has to manually scroll up to make it visible. The code in question is in myCollectionView_Loaded. It shouldn't be neccessary to scroll to element 1 for android and element 0 for Windows to scroll over the header-element. I don't know the behavior under other platforms like iOS, but I assume the correct behaviour is the one for Windows (scrolling to 0 instead of 1).