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[iOS] CollectionView2 - empty view - improvements2 #29154

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[iOS] CollectionView2 - empty view - improvements2 #29154

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13 changes: 11 additions & 2 deletions src/Controls/src/Core/Handlers/Items2/ItemsViewHandler2.iOS.cs
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Original file line number Diff line number Diff line change
@@ -1,5 +1,6 @@
#nullable disable
using System;
using System.Collections;
using System.Collections.Generic;
using System.Text;
using CoreGraphics;
Expand Down Expand Up @@ -97,12 +98,20 @@ public static void MapItemTemplate(ItemsViewHandler2<TItemsView> handler, ItemsV

public static void MapEmptyView(ItemsViewHandler2<TItemsView> handler, ItemsView itemsView)
{
handler.Controller?.UpdateEmptyView();
UpdateEmptyView(handler, itemsView);
}

public static void MapEmptyViewTemplate(ItemsViewHandler2<TItemsView> handler, ItemsView itemsView)
{
handler.Controller?.UpdateEmptyView();
UpdateEmptyView(handler, itemsView);
}

private static void UpdateEmptyView(ItemsViewHandler2<TItemsView> handler, ItemsView itemsView)
{
if (itemsView.ItemsSource is null || itemsView.ItemsSource is IList list && list.Count == 0)
{
handler.Controller?.CollectionView.ReloadItems(handler.Controller?.CollectionView.IndexPathsForVisibleItems);
}
}

public static void MapFlowDirection(ItemsViewHandler2<TItemsView> handler, ItemsView itemsView)
Expand Down
4 changes: 4 additions & 0 deletions src/Controls/src/Core/Handlers/Items2/iOS/ItemsViewCell2.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -32,6 +32,10 @@ private protected void SetupPlatformView(UIView platformView, bool autoLayout =
{
ContentView.TranslatesAutoresizingMaskIntoConstraints = false;

foreach (var subview in ContentView.Subviews)
{
subview.RemoveFromSuperview();
}
ContentView.AddSubview(platformView);

// We want the cell to be the same size as the ContentView
Expand Down
209 changes: 24 additions & 185 deletions src/Controls/src/Core/Handlers/Items2/iOS/ItemsViewController2.cs
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Original file line number Diff line number Diff line change
@@ -1,14 +1,11 @@
#nullable disable
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Diagnostics.CodeAnalysis;
using System.Linq;
using CoreGraphics;
using Foundation;
using Microsoft.Maui.Controls.Internals;
using Microsoft.Maui.Graphics;
using PassKit;
using UIKit;

namespace Microsoft.Maui.Controls.Handlers.Items2
Expand All @@ -31,13 +28,9 @@ public abstract class ItemsViewController2<TItemsView> : UICollectionViewControl
protected UICollectionViewLayout ItemsViewLayout { get; set; }

bool _initialized;
bool _isEmpty = true;
bool _emptyViewDisplayed;
bool _disposed;

[UnconditionalSuppressMessage("Memory", "MEM0002", Justification = "Proven safe in test: MemoryTests.HandlerDoesNotLeak")]
UIView _emptyUIView;
VisualElement _emptyViewFormsElement;
List<string> _cellReuseIds = new List<string>();
CGSize _previousContentSize;

Expand Down Expand Up @@ -93,11 +86,6 @@ protected override void Dispose(bool disposing)
CollectionView.Delegate = null;
Delegator?.Dispose();

_emptyUIView?.Dispose();
_emptyUIView = null;

_emptyViewFormsElement = null;

ItemsViewLayout?.Dispose();
CollectionView?.Dispose();
}
Expand All @@ -107,6 +95,11 @@ protected override void Dispose(bool disposing)

public override UICollectionViewCell GetCell(UICollectionView collectionView, NSIndexPath indexPath)
{
if (ItemsSource.ItemCount == 0)
{
return GetEmptyViewCell(collectionView, indexPath);
}

var cell = collectionView.DequeueReusableCell(DetermineCellReuseId(indexPath), indexPath) as UICollectionViewCell;

// We need to get the index path that is adjusted for the item source
Expand All @@ -127,31 +120,30 @@ public override UICollectionViewCell GetCell(UICollectionView collectionView, NS
return cell;
}

public override nint GetItemsCount(UICollectionView collectionView, nint section)
protected UICollectionViewCell GetEmptyViewCell(UICollectionView collectionView, NSIndexPath indexPath, double headerHeight = 0, double footerHeight = 0)
{
CheckForEmptySource();
if (ItemsSource.ItemCount == 0 && ItemsView?.EmptyView is View emptyView)
{
var emptyViewCell = collectionView.DequeueReusableCell("EmptyViewCell", indexPath) as TemplatedCell2;
emptyViewCell.ScrollDirection = ScrollDirection;
emptyViewCell.Unbind();
emptyViewCell.PlatformHandler = null;

return ItemsSource.ItemCountInGroup(section);
emptyViewCell.Bind(emptyView, ItemsView);
return emptyViewCell;
}
return null;
}

void CheckForEmptySource()
public override nint GetItemsCount(UICollectionView collectionView, nint section)
{
var wasEmpty = _isEmpty;

_isEmpty = ItemsSource.ItemCount == 0;

if (wasEmpty != _isEmpty)
// If the ItemsSource is empty, we need to return 1 so that the empty view can be displayed
if (ItemsSource.ItemCount == 0 && ItemsView?.EmptyView is not null)
{
UpdateEmptyViewVisibility(_isEmpty);
return 1;
}

if (wasEmpty && !_isEmpty)
{
// If we're going from empty to having stuff, it's possible that we've never actually measured
// a prototype cell and our itemSize or estimatedItemSize are wrong/unset
// So trigger a constraint update; if we need a measurement, that will make it happen
// TODO: Fix ItemsViewLayout.ConstrainTo(CollectionView.Bounds.Size);
}
return ItemsSource.ItemCountInGroup(section);
}

public override void ViewDidLoad()
Expand Down Expand Up @@ -199,7 +191,6 @@ public override void ViewWillLayoutSubviews()
}

base.ViewWillLayoutSubviews();
LayoutEmptyView();
InvalidateMeasureIfContentSizeChanged();
}

Expand Down Expand Up @@ -260,8 +251,6 @@ void EnsureLayoutInitialized()
CollectionView.Delegate = Delegator;

CollectionView.SetCollectionViewLayout(ItemsViewLayout, false);

UpdateEmptyView();
}

protected virtual UICollectionViewDelegateFlowLayout CreateDelegator()
Expand All @@ -288,12 +277,6 @@ public virtual void UpdateItemsSource()
public virtual void UpdateFlowDirection()
{
CollectionView.UpdateFlowDirection(ItemsView);

if (_emptyViewDisplayed)
{
AlignEmptyView();
}

Layout.InvalidateLayout();
}

Expand All @@ -305,12 +288,11 @@ public override nint NumberOfSections(UICollectionView collectionView)
// To handle this scenario, we check if ItemsSource is null before proceeding.
// In iOS 17 and later versions, this behavior works properly, as the method is no longer called prematurely.
// To ensure compatibility with older iOS versions, we include this null check and return 0 if ItemsSource is null.
if (ItemsSource == null)
if (ItemsSource.ItemCount == 0 && ItemsView?.EmptyView is not null)
{
return 0;
return 1;
}

CheckForEmptySource();
return ItemsSource.GroupCount;
}

Expand Down Expand Up @@ -358,16 +340,11 @@ protected virtual void RegisterViewTypes()
CollectionView.RegisterClassForCell(typeof(VerticalDefaultCell2), VerticalDefaultCell2.ReuseId);
CollectionView.RegisterClassForCell(typeof(HorizontalCell2), HorizontalCell2.ReuseId);
CollectionView.RegisterClassForCell(typeof(VerticalCell2), VerticalCell2.ReuseId);
CollectionView.RegisterClassForCell(typeof(TemplatedCell2), "EmptyViewCell");
}

protected abstract bool IsHorizontal { get; }

protected virtual CGRect DetermineEmptyViewFrame()
{
return new CGRect(CollectionView.Frame.X, CollectionView.Frame.Y,
CollectionView.Frame.Width, CollectionView.Frame.Height);
}

void InvalidateMeasureIfContentSizeChanged()
{
if (CollectionView?.CollectionViewLayout?.CollectionViewContentSize is not { } contentSize)
Expand Down Expand Up @@ -418,11 +395,6 @@ void InvalidateMeasureIfContentSizeChanged()

internal Size GetSize()
{
if (_emptyViewDisplayed)
{
return _emptyUIView.Frame.Size.ToSize();
}

return CollectionView.CollectionViewLayout.CollectionViewContentSize.ToSize();
}

Expand All @@ -448,139 +420,6 @@ internal void UpdateView(object view, DataTemplate viewTemplate, ref UIView uiVi
}
}

internal void UpdateEmptyView()
{
if (!_initialized)
{
return;
}

// Get rid of the old view
TearDownEmptyView();

// Set up the new empty view
UpdateView(ItemsView?.EmptyView, ItemsView?.EmptyViewTemplate, ref _emptyUIView, ref _emptyViewFormsElement);

// We may need to show the updated empty view
UpdateEmptyViewVisibility(ItemsSource?.ItemCount == 0);
}

void UpdateEmptyViewVisibility(bool isEmpty)
{
if (!_initialized)
{
return;
}

if (isEmpty)
{
ShowEmptyView();
}
else
{
HideEmptyView();
}
}

void AlignEmptyView()
{
if (_emptyUIView == null)
{
return;
}

bool isRtl;

if (OperatingSystem.IsIOSVersionAtLeast(10) || OperatingSystem.IsTvOSVersionAtLeast(10))
isRtl = CollectionView.EffectiveUserInterfaceLayoutDirection == UIUserInterfaceLayoutDirection.RightToLeft;
else
isRtl = CollectionView.SemanticContentAttribute == UISemanticContentAttribute.ForceRightToLeft;

if (isRtl)
{
if (_emptyUIView.Transform.A == -1)
{
return;
}

FlipEmptyView();
}
else
{
if (_emptyUIView.Transform.A == -1)
{
FlipEmptyView();
}
}
}

void FlipEmptyView()
{
// Flip the empty view 180 degrees around the X axis
_emptyUIView.Transform = CGAffineTransform.Scale(_emptyUIView.Transform, -1, 1);
}

void ShowEmptyView()
{
if (_emptyViewDisplayed || _emptyUIView == null)
{
return;
}

_emptyUIView.Tag = EmptyTag;
CollectionView.AddSubview(_emptyUIView);

if (((IElementController)ItemsView).LogicalChildren.IndexOf(_emptyViewFormsElement) == -1)
{
ItemsView.AddLogicalChild(_emptyViewFormsElement);
}

LayoutEmptyView();

AlignEmptyView();
_emptyViewDisplayed = true;
}

void HideEmptyView()
{
if (!_emptyViewDisplayed || _emptyUIView == null)
{
return;
}

_emptyUIView.RemoveFromSuperview();

_emptyViewDisplayed = false;
}

void TearDownEmptyView()
{
HideEmptyView();

// RemoveLogicalChild will trigger a disposal of the native view and its content
ItemsView.RemoveLogicalChild(_emptyViewFormsElement);

_emptyUIView = null;
_emptyViewFormsElement = null;
}

virtual internal CGRect LayoutEmptyView()
{
if (!_initialized || _emptyUIView == null || _emptyUIView.Superview == null)
{
return CGRect.Empty;
}

var frame = DetermineEmptyViewFrame();

_emptyUIView.Frame = frame;

if (_emptyViewFormsElement != null && ((IElementController)ItemsView).LogicalChildren.IndexOf(_emptyViewFormsElement) != -1)
_emptyViewFormsElement.Layout(frame.ToRectangle());

return frame;
}

internal protected virtual void UpdateVisibility()
{
if (ItemsView.IsVisible)
Expand Down
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