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Use ItemsSourceView in ItemsControl.
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Fixes #54.
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@grokys
grokys committed Dec 9, 2022
1 parent 627d9c5 commit 3195df0
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Showing 13 changed files with 244 additions and 313 deletions.
2 changes: 1 addition & 1 deletion src/Avalonia.Controls/Carousel.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -48,7 +48,7 @@ public IPageTransition? PageTransition
/// </summary>
public void Next()
{
if (SelectedIndex < Items.Count() - 1)
if (SelectedIndex < ItemCount - 1)
{
++SelectedIndex;
}
Expand Down
221 changes: 69 additions & 152 deletions src/Avalonia.Controls/ItemsControl.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -2,15 +2,14 @@
using System.Collections;
using System.Collections.Generic;
using System.Collections.Specialized;
using System.Linq;
using System.Diagnostics.CodeAnalysis;
using Avalonia.Automation.Peers;
using Avalonia.Collections;
using Avalonia.Controls.Generators;
using Avalonia.Controls.Metadata;
using Avalonia.Controls.Presenters;
using Avalonia.Controls.Primitives;
using Avalonia.Controls.Templates;
using Avalonia.Controls.Utils;
using Avalonia.Data;
using Avalonia.Input;
using Avalonia.LogicalTree;
Expand All @@ -24,7 +23,7 @@ namespace Avalonia.Controls
/// Displays a collection of items.
/// </summary>
[PseudoClasses(":empty", ":singleitem")]
public class ItemsControl : TemplatedControl, IItemsPresenterHost, ICollectionChangedListener, IChildIndexProvider
public class ItemsControl : TemplatedControl, IItemsPresenterHost, IChildIndexProvider
{
/// <summary>
/// The default value for the <see cref="ItemsPanel"/> property.
Expand Down Expand Up @@ -62,6 +61,11 @@ public class ItemsControl : TemplatedControl, IItemsPresenterHost, ICollectionCh
public static readonly StyledProperty<IDataTemplate?> ItemTemplateProperty =
AvaloniaProperty.Register<ItemsControl, IDataTemplate?>(nameof(ItemTemplate));

/// <summary>
/// Defines the <see cref="ItemsView"/> property.
/// </summary>
public static readonly DirectProperty<ItemsControl, ItemsSourceView> ItemsViewProperty =
AvaloniaProperty.RegisterDirect<ItemsControl, ItemsSourceView>(nameof(Items), o => o.ItemsView);

/// <summary>
/// Defines the <see cref="DisplayMemberBinding" /> property
Expand All @@ -80,27 +84,21 @@ public IBinding? DisplayMemberBinding
}

private IEnumerable? _items = new AvaloniaList<object>();
private ItemsSourceView _itemsView;
private int _itemCount;
private ItemContainerGenerator? _itemContainerGenerator;
private EventHandler<ChildIndexChangedEventArgs>? _childIndexChanged;
private IDataTemplate? _displayMemberItemTemplate;
private Tuple<int, Control>? _containerBeingPrepared;

/// <summary>
/// Initializes static members of the <see cref="ItemsControl"/> class.
/// </summary>
static ItemsControl()
{
ItemsProperty.Changed.AddClassHandler<ItemsControl>((x, e) => x.ItemsChanged(e));
}

/// <summary>
/// Initializes a new instance of the <see cref="ItemsControl"/> class.
/// </summary>
public ItemsControl()
{
_itemsView = new(_items);
_itemsView.PostCollectionChanged += ItemsCollectionChanged;
UpdatePseudoClasses(0);
SubscribeToItems(_items);
}

/// <summary>
Expand Down Expand Up @@ -164,6 +162,33 @@ public IDataTemplate? ItemTemplate
/// </summary>
public ItemsPresenter? Presenter { get; private set; }

/// <summary>
/// Gets a standardized view over <see cref="Items"/>.
/// </summary>
/// <remarks>
/// The <see cref="Items"/> property may be an enumerable which does not implement
/// <see cref="IList"/> or may be null. This view can be used to provide a standardized
/// view of the current items regardless of the type of the concrete collection, and
/// without having to deal with null values.
/// </remarks>
public ItemsSourceView ItemsView
{
get => _itemsView;
private set
{
if (ReferenceEquals(_itemsView, value))
return;

var oldValue = _itemsView;
RemoveControlItemsFromLogicalChildren(_itemsView);
_itemsView.PostCollectionChanged -= ItemsCollectionChanged;
_itemsView = value;
_itemsView.PostCollectionChanged += ItemsCollectionChanged;
AddControlItemsToLogicalChildren(_itemsView);
RaisePropertyChanged(ItemsViewProperty, oldValue, _itemsView);
}
}

private protected bool WrapFocus { get; set; }

event EventHandler<ChildIndexChangedEventArgs>? IChildIndexProvider.ChildIndexChanged
Expand Down Expand Up @@ -192,7 +217,7 @@ event EventHandler<ChildIndexChangedEventArgs>? IChildIndexProvider.ChildIndexCh
/// </returns>
public Control? ContainerFromItem(object item)
{
var index = Items?.IndexOf(item) ?? -1;
var index = ItemsView.IndexOf(item);
return index >= 0 ? ContainerFromIndex(index) : null;
}

Expand All @@ -216,7 +241,7 @@ event EventHandler<ChildIndexChangedEventArgs>? IChildIndexProvider.ChildIndexCh
public object? ItemFromContainer(Control container)
{
var index = IndexFromContainer(container);
return index >= 0 && index < ItemCount ? Items!.ElementAt(index) : null;
return index >= 0 && index < ItemsView.Count ? ItemsView[index] : null;
}

/// <summary>
Expand All @@ -231,37 +256,6 @@ void IItemsPresenterHost.RegisterItemsPresenter(ItemsPresenter presenter)
_childIndexChanged?.Invoke(this, ChildIndexChangedEventArgs.Empty);
}

void ICollectionChangedListener.PreChanged(INotifyCollectionChanged sender, NotifyCollectionChangedEventArgs e)
{
}

void ICollectionChangedListener.Changed(INotifyCollectionChanged sender, NotifyCollectionChangedEventArgs e)
{
}

void ICollectionChangedListener.PostChanged(INotifyCollectionChanged sender, NotifyCollectionChangedEventArgs e)
{
ItemsCollectionChanged(sender, e);
}

/// <summary>
/// Gets the item at the specified index in a collection.
/// </summary>
/// <param name="items">The collection.</param>
/// <param name="index">The index.</param>
/// <returns>The item at the given index or null if the index is out of bounds.</returns>
protected static object? ElementAt(IEnumerable? items, int index)
{
if (index != -1 && index < items.Count())
{
return items!.ElementAt(index) ?? null;
}
else
{
return null;
}
}

/// <summary>
/// Creates or a container that can be used to display an item.
/// </summary>
Expand Down Expand Up @@ -350,41 +344,6 @@ protected internal virtual void ClearContainerForItemOverride(Control container)
// the WPF source it seems that this isn't done there.
}

/// <summary>
/// Gets the index of an item in a collection.
/// </summary>
/// <param name="items">The collection.</param>
/// <param name="item">The item.</param>
/// <returns>The index of the item or -1 if the item was not found.</returns>
protected static int IndexOf(IEnumerable? items, object item)
{
if (items != null && item != null)
{
var list = items as IList;

if (list != null)
{
return list.IndexOf(item);
}
else
{
int index = 0;

foreach (var i in items)
{
if (Equals(i, item))
{
return index;
}

++index;
}
}
}

return -1;
}

/// <summary>
/// Determines whether the specified item is (or is eligible to be) its own container.
/// </summary>
Expand Down Expand Up @@ -445,7 +404,12 @@ protected override void OnPropertyChanged(AvaloniaPropertyChangedEventArgs chang
{
base.OnPropertyChanged(change);

if (change.Property == ItemCountProperty)
if (change.Property == ItemsProperty)
{
ItemsView = ItemsSourceView.GetOrCreate(change.GetNewValue<IEnumerable?>());
ItemCount = ItemsView.Count;
}
else if (change.Property == ItemCountProperty)
{
UpdatePseudoClasses(change.GetNewValue<int>());
}
Expand All @@ -468,26 +432,6 @@ protected override void OnPropertyChanged(AvaloniaPropertyChangedEventArgs chang
}
}

/// <summary>
/// Called when the <see cref="Items"/> property changes.
/// </summary>
/// <param name="e">The event args.</param>
protected virtual void ItemsChanged(AvaloniaPropertyChangedEventArgs e)
{
var oldValue = e.OldValue as IEnumerable;
var newValue = e.NewValue as IEnumerable;

if (oldValue is INotifyCollectionChanged incc)
{
CollectionChangedEventManager.Instance.RemoveListener(incc, this);
}

UpdateItemCount();
RemoveControlItemsFromLogicalChildren(oldValue);
AddControlItemsToLogicalChildren(newValue);
SubscribeToItems(newValue);
}

/// <summary>
/// Refreshes the containers displayed by the control.
/// </summary>
Expand All @@ -502,9 +446,9 @@ protected virtual void ItemsChanged(AvaloniaPropertyChangedEventArgs e)
/// </summary>
/// <param name="sender">The event sender.</param>
/// <param name="e">The event args.</param>
protected virtual void ItemsCollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
protected virtual void ItemsCollectionChanged(object? sender, NotifyCollectionChangedEventArgs e)
{
UpdateItemCount();
ItemCount = _itemsView.Count;

switch (e.Action)
{
Expand Down Expand Up @@ -576,22 +520,22 @@ internal void ItemContainerIndexChanged(Control container, int oldIndex, int new
/// <param name="items">The items.</param>
private void AddControlItemsToLogicalChildren(IEnumerable? items)
{
var toAdd = new List<ILogical>();
if (items is null)
return;

if (items != null)
List<ILogical>? toAdd = null;

foreach (var i in items)
{
foreach (var i in items)
if (i is Control control && !LogicalChildren.Contains(control))
{
var control = i as Control;

if (control != null && !LogicalChildren.Contains(control))
{
toAdd.Add(control);
}
toAdd ??= new();
toAdd.Add(control);
}
}

LogicalChildren.AddRange(toAdd);
if (toAdd is not null)
LogicalChildren.AddRange(toAdd);
}

/// <summary>
Expand All @@ -600,34 +544,22 @@ private void AddControlItemsToLogicalChildren(IEnumerable? items)
/// <param name="items">The items.</param>
private void RemoveControlItemsFromLogicalChildren(IEnumerable? items)
{
var toRemove = new List<ILogical>();
if (items is null)
return;

if (items != null)
List<ILogical>? toRemove = null;

foreach (var i in items)
{
foreach (var i in items)
if (i is Control control)
{
var control = i as Control;

if (control != null)
{
toRemove.Add(control);
}
toRemove ??= new();
toRemove.Add(control);
}
}

LogicalChildren.RemoveAll(toRemove);
}

/// <summary>
/// Subscribes to an <see cref="Items"/> collection.
/// </summary>
/// <param name="items">The items collection.</param>
private void SubscribeToItems(IEnumerable? items)
{
if (items is INotifyCollectionChanged incc)
{
CollectionChangedEventManager.Instance.AddListener(incc, this);
}
if (toRemove is not null)
LogicalChildren.RemoveAll(toRemove);
}

private IDataTemplate? GetEffectiveItemTemplate()
Expand All @@ -647,22 +579,6 @@ private void SubscribeToItems(IEnumerable? items)
return _displayMemberItemTemplate;
}

private void UpdateItemCount()
{
if (Items == null)
{
ItemCount = 0;
}
else if (Items is IList list)
{
ItemCount = list.Count;
}
else
{
ItemCount = Items.Count();
}
}

private void UpdatePseudoClasses(int itemCount)
{
PseudoClasses.Set(":empty", itemCount == 0);
Expand Down Expand Up @@ -728,7 +644,8 @@ int IChildIndexProvider.GetChildIndex(ILogical child)

bool IChildIndexProvider.TryGetTotalCount(out int count)
{
return Items.TryGetCountFast(out count);
count = ItemsView.Count;
return true;
}
}
}
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