Fix VirtualScroll memory leaks

Author: albyrock87

Source/Nalu.Maui.VirtualScroll/Platforms/Apple/VirtualScrollCell.cs

@@ -44,7 +44,7 @@ public UIView? NativeView
         private set => _nativeView = value;
     }
 
-    public new VirtualScrollCellContent ContentView { get; } 
+    public new VirtualScrollCellContent ContentView { get; private set; } 
 
     [Export("initWithFrame:")]
     public VirtualScrollCell(CGRect frame) : base(frame)
@@ -195,4 +195,18 @@ public override void PrepareForReuse()
         _readyForReuse = true;
         _needsMeasure = false;
     }
+
+    protected override void Dispose(bool disposing)
+    {
+        base.Dispose(disposing);
+
+        if (disposing)
+        {
+            ItemsLayout = null;
+            VirtualView = null;
+            NativeView = null;
+            SupplementaryType = null;
+            IndexPath = null;
+        }
+    }
 }

Source/Nalu.Maui.VirtualScroll/Platforms/Apple/VirtualScrollCollectionView.cs

@@ -22,8 +22,8 @@ public class VirtualScrollCollectionView : UICollectionView, IVirtualScrollCells
     , Microsoft.Maui.Platform.IPlatformMeasureInvalidationController
 #endif
 {
-    private readonly IVirtualScrollLayoutInfo _layoutInfo;
-    private readonly VirtualScrollCellManager<VirtualScrollCell> _cellManager = new(cell => cell.VirtualView);
+    private IVirtualScrollLayoutInfo _layoutInfo;
+    private VirtualScrollCellManager<VirtualScrollCell> _cellManager = new(cell => cell.VirtualView);
     private readonly List<NSIndexPath> _invalidatedGlobalHeaders = new(2);
     private readonly List<NSIndexPath> _invalidatedGlobalFooters = new(2);
     private readonly List<NSIndexPath> _invalidatedSectionHeaders = new(8);
@@ -206,6 +206,13 @@ protected override void Dispose(bool disposing)
         if (disposing)
         {
             _cellManager.Dispose();
+            _cellManager = null!;
+            _layoutInfo = null!;
+            _invalidatedGlobalFooters.Clear();
+            _invalidatedGlobalHeaders.Clear();
+            _invalidatedSectionFooters.Clear();
+            _invalidatedSectionHeaders.Clear();
+            _invalidatedPaths.Clear();
         }
     }
 

Source/Nalu.Maui.VirtualScroll/Platforms/Apple/VirtualScrollHandler.cs

@@ -111,8 +111,6 @@ protected override UIView CreatePlatformView()
 
         layoutSetup.ConfigureCollectionView(collectionView);
 
-        _dragGestureRecognizer = CreateDragGestureRecognizer(virtualScroll, collectionView);
-
         _reuseIdManager = reuseIdManager;
         _collectionView = collectionView;
 
@@ -170,49 +168,60 @@ private void RefreshControlEventHandler(object? sender, EventArgs e)
         }
     }
 
-    private static UILongPressGestureRecognizer CreateDragGestureRecognizer(IVirtualScroll virtualView, VirtualScrollCollectionView collectionView)
-        => new(gesture =>
+    private static UILongPressGestureRecognizer CreateDragGestureRecognizer()
+        => new(HandleLongPress);
+
+    // ReSharper disable once MemberCanBeMadeStatic.Local
+    private static void HandleLongPress(UILongPressGestureRecognizer gesture)
+    {
+        if (gesture.View is not VirtualScrollCollectionView cv)
+        {
+            return;
+        }
+
+        switch (gesture.State)
+        {
+            case UIGestureRecognizerState.Began:
             {
-                switch (gesture.State)
+                var location = gesture.LocationInView(cv);
+                var indexPath = cv.IndexPathForItemAtPoint(location);
+
+                if (indexPath is not null && cv.CellForItem(indexPath) is { } cell)
                 {
-                    case UIGestureRecognizerState.Began:
-                    {
-                        var location = gesture.LocationInView(collectionView);
-                        var indexPath = collectionView.IndexPathForItemAtPoint(location);
-                        if (indexPath is not null && collectionView.CellForItem(indexPath) is { } cell)
-                        {
-                            ((VirtualScrollDelegate)collectionView.Delegate).ItemDragInitiating(indexPath);
-                            indexPath = collectionView.IndexPathForCell(cell);
-                            if (indexPath is not null)
-                            {
-                                collectionView.BeginInteractiveMovementForItem(indexPath);
-                            }
-                        }
-
-                        break;
-                    }
-                    case UIGestureRecognizerState.Changed:
-                    {
-                        var location = gesture.LocationInView(collectionView);
-                        collectionView.UpdateInteractiveMovement(location);
+                    ((VirtualScrollDelegate) cv.Delegate).ItemDragInitiating(indexPath);
+                    indexPath = cv.IndexPathForCell(cell);
 
-                        break;
-                    }
-                    case UIGestureRecognizerState.Ended:
-                    {
-                        collectionView.EndInteractiveMovement();
-                        ((VirtualScrollDelegate)collectionView.Delegate).ItemDragEnded();
-                        break;
-                    }
-                    default:
+                    if (indexPath is not null)
                     {
-                        collectionView.CancelInteractiveMovement();
-                        ((VirtualScrollDelegate)collectionView.Delegate).ItemDragEnded();
-                        break;
+                        cv.BeginInteractiveMovementForItem(indexPath);
                     }
                 }
+
+                break;
             }
-        );
+            case UIGestureRecognizerState.Changed:
+            {
+                var location = gesture.LocationInView(cv);
+                cv.UpdateInteractiveMovement(location);
+
+                break;
+            }
+            case UIGestureRecognizerState.Ended:
+            {
+                cv.EndInteractiveMovement();
+                ((VirtualScrollDelegate) cv.Delegate).ItemDragEnded();
+
+                break;
+            }
+            default:
+            {
+                cv.CancelInteractiveMovement();
+                ((VirtualScrollDelegate) cv.Delegate).ItemDragEnded();
+
+                break;
+            }
+        }
+    }
 
     private void OnBoundsChanged(object? sender, EventArgs e)
     {
@@ -316,9 +325,14 @@ protected override void DisconnectHandler(UIView platformView)
         _delegate?.Dispose();
         _delegate = null;
 
+        if (_dragGestureRecognizer is not null)
+        {
+            _collectionView?.RemoveGestureRecognizer(_dragGestureRecognizer);
+            _dragGestureRecognizer.Dispose();
+            _dragGestureRecognizer = null;
+        }
         _collectionView?.Dispose();
         _collectionView = null;
-        _dragGestureRecognizer?.Dispose();
         _containerView?.Dispose();
         _containerView = null;
         _lastBounds = CGSize.Empty;
@@ -336,16 +350,17 @@ public static void MapDragHandler(VirtualScrollHandler handler, IVirtualScroll v
     {
         var collectionView = handler.PlatformCollectionView;
         var isDragEnabled = virtualScroll.DragHandler is not null;
-        var dragGestureRecognizer = handler._dragGestureRecognizer ?? throw new InvalidOperationException("Drag gesture recognizer is not initialized.");
-
+        
         if (isDragEnabled)
         {
-            
-            collectionView.AddGestureRecognizer(dragGestureRecognizer);
+            handler._dragGestureRecognizer ??= CreateDragGestureRecognizer();
+            collectionView.AddGestureRecognizer(handler._dragGestureRecognizer);
         }
-        else
+        else if (handler._dragGestureRecognizer is not null)
         {
-            collectionView.RemoveGestureRecognizer(dragGestureRecognizer);
+            collectionView.RemoveGestureRecognizer(handler._dragGestureRecognizer);
+            handler._dragGestureRecognizer.Dispose();
+            handler._dragGestureRecognizer = null;
         }
     }
 
@@ -407,10 +422,37 @@ public static void MapLayout(VirtualScrollHandler handler, IVirtualScroll virtua
             handler._delegate?.UpdateFadingEdge(handler._collectionView);
         }
     }
+
+    private struct VirtualScrollLayoutInfo : IVirtualScrollLayoutInfo
+    {
+        public VirtualScrollLayoutInfo(IVirtualScrollLayoutInfo virtualScroll)
+        {
+            HasGlobalFooter = virtualScroll.HasGlobalFooter;
+            HasGlobalHeader = virtualScroll.HasGlobalHeader;
+            HasSectionFooter = virtualScroll.HasSectionFooter;
+            HasSectionHeader = virtualScroll.HasSectionHeader;
+        }
+        
+        public bool Equals(IVirtualScrollLayoutInfo? other) =>
+            other != null &&
+            HasGlobalFooter == other.HasGlobalFooter &&
+            HasGlobalHeader == other.HasGlobalHeader &&
+            HasSectionFooter == other.HasSectionFooter &&
+            HasSectionHeader == other.HasSectionHeader;
+            
+
+        public bool HasGlobalHeader { get; }
+        public bool HasGlobalFooter { get; }
+        public bool HasSectionHeader { get; }
+        public bool HasSectionFooter { get; }
+    }
 
     private static VirtualScrollCollectionViewLayoutSetup CreatePlatformLayout(VirtualScrollHandler handler, IVirtualScroll virtualScroll)
     {
-        var layoutInfo = virtualScroll as IVirtualScrollLayoutInfo ?? throw new InvalidOperationException("The provided IVirtualScroll does not implement IVirtualScrollLayoutInfo interface.");
+        var layoutInfo = new VirtualScrollLayoutInfo(
+            virtualScroll as IVirtualScrollLayoutInfo ??
+            throw new InvalidOperationException("The provided IVirtualScroll does not implement IVirtualScrollLayoutInfo interface.")
+        );
 
         var layoutSetup = virtualScroll.ItemsLayout switch
         {