ScrollToOnFocusBehaviour.cs

using System.ComponentModel;
using System.Diagnostics;
using NeuroAccessMaui.UI.Controls;
using Waher.Script.Constants;
 
namespace NeuroAccessMaui.UI.Behaviors
{
    public class ScrollToOnFocusBehavior : Behavior<VisualElement>
    {
        [TypeConverter(typeof(ReferenceTypeConverter))]
        public ScrollView? TargetScrollView { get; set; }
 
        [TypeConverter(typeof(ReferenceTypeConverter))]
        public VisualElement? TargetElement { get; set; }
 
        public ScrollToPosition ScrollToPosition { get; set; } = ScrollToPosition.Start;
 
        public static readonly BindableProperty IsEnabledProperty =
            BindableProperty.Create(nameof(IsEnabled), typeof(bool), typeof(ScrollToClickedBehavior), true);
 
        public bool IsEnabled
        {
            get => (bool)this.GetValue(IsEnabledProperty);
            set => this.SetValue(IsEnabledProperty, value);
        }
 
        protected override void OnAttachedTo(VisualElement bindable)
        {
 
            base.OnAttachedTo(bindable);
 
            if(bindable is CompositeEntry entry)
                entry.Entry.Focused += this.OnElementFocused;
            else
                bindable.Focused += this.OnElementFocused;
        }
 
        protected override void OnDetachingFrom(VisualElement bindable)
        {
            base.OnDetachingFrom(bindable);
            if(bindable is CompositeEntry entry)
                entry.Entry.Focused -= this.OnElementFocused;
            else
                bindable.Focused -= this.OnElementFocused;
        }
 
        private async void OnElementFocused(object? sender, FocusEventArgs e)
        {
            if(sender is null or not VisualElement)
            {
                return;
            }
            if(sender is CompositeEntry or Entry)
                await Task.Delay(200); //allow keyboard to show if there is any
 
            VisualElement? target = this.TargetElement ?? (VisualElement)sender;
 
            if (this.TargetScrollView is not null)
            {
                await this.TargetScrollView.ScrollToAsync(target, ScrollToPosition.Start, true);
            }
            else
            {
                Element Loop = ((VisualElement)sender).Parent;
 
                while (Loop is not null && Loop is not ScrollView)
                    Loop = Loop.Parent;
 
                (Loop as ScrollView)?.ScrollToAsync(target, this.ScrollToPosition, true);
            }
        }
    }
}