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Change SelectedItems to HashSet, add SelectMany method #50

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Change SelectedItems to HashSet, add SelectMany method #50

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42 changes: 29 additions & 13 deletions VirtualListView/Controls/VirtualListView.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -247,20 +247,20 @@ public ICommand? ScrolledCommand
}

public static readonly BindableProperty SelectedItemsProperty =
BindableProperty.Create(nameof(SelectedItems), typeof(IList<ItemPosition>), typeof(VirtualListView), Array.Empty<ItemPosition>(),
BindableProperty.Create(nameof(SelectedItems), typeof(ISet<ItemPosition>), typeof(VirtualListView), new HashSet<ItemPosition>(),
propertyChanged: (bindableObj, oldValue, newValue) =>
{
if (bindableObj is VirtualListView vlv
&& oldValue is IList<ItemPosition> oldSelection
&& newValue is IList<ItemPosition> newSelection)
&& oldValue is ISet<ItemPosition> oldSelection
&& newValue is ISet<ItemPosition> newSelection)
{
vlv.RaiseSelectedItemsChanged(oldSelection.ToArray(), newSelection.ToArray());
}
});
public IList<ItemPosition>? SelectedItems
public ISet<ItemPosition>? SelectedItems
{
get => (IList<ItemPosition>)GetValue(SelectedItemsProperty);
set => SetValue(SelectedItemsProperty, value ?? Array.Empty<ItemPosition>());
get => (ISet<ItemPosition>?)GetValue(SelectedItemsProperty);
set => SetValue(SelectedItemsProperty, value ?? new HashSet<ItemPosition>());
}

public static readonly BindableProperty SelectedItemProperty =
Expand All @@ -272,7 +272,7 @@ public IList<ItemPosition>? SelectedItems
if (newValue is null || newValue is not ItemPosition)
vlv.SelectedItems = null;
else if (newValue is ItemPosition p)
vlv.SelectedItems = new[] { p };
vlv.SelectedItems = new HashSet<ItemPosition>(){p};
}
});

Expand All @@ -294,11 +294,11 @@ public void DeselectItem(ItemPosition itemPosition)
}
else if (SelectionMode == Maui.SelectionMode.Multiple)
{
var current = SelectedItems.ToList();
if (current.Contains(itemPosition))
if (SelectedItems?.Contains(itemPosition) ?? false)
{
var current = SelectedItems.ToHashSet();
current.Remove(itemPosition);
SelectedItems = current.ToArray();
SelectedItems = current;
}
}
}
Expand All @@ -314,10 +314,26 @@ public void SelectItem(ItemPosition itemPosition)
}
else if (SelectionMode == Maui.SelectionMode.Multiple)
{
var current = SelectedItems;
if (current is null || !current.Contains(itemPosition))
if (!(SelectedItems?.Contains(itemPosition) ?? false))
{
SelectedItems = (current ?? []).Append(itemPosition).ToArray();
var current = SelectedItems?.ToHashSet() ?? [];
current.Add(itemPosition);
SelectedItems = current;
}
}
}

public void SelectMany(IEnumerable<ItemPosition> items)
{
if (SelectionMode == Maui.SelectionMode.Multiple)
{
if (items.Any(i => !(SelectedItems?.Contains(i) ?? false)))
{
var current = (SelectedItems ?? Enumerable.Empty<ItemPosition>())
.Concat(items)
.ToHashSet();

SelectedItems = current;
}
}
}
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2 changes: 1 addition & 1 deletion VirtualListView/IVirtualListView.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -22,7 +22,7 @@ public interface IVirtualListView : IView

SelectionMode SelectionMode { get; }

IList<ItemPosition> SelectedItems { get; set; }
ISet<ItemPosition> SelectedItems { get; set; }

ItemPosition? SelectedItem { get; set; }

Expand Down
2 changes: 2 additions & 0 deletions VirtualListView/ItemPosition.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -15,4 +15,6 @@ public ItemPosition(int sectionIndex = 0, int itemIndex = 0)

public bool Equals(ItemPosition other)
=> SectionIndex == other.SectionIndex && ItemIndex == other.ItemIndex;
public override int GetHashCode()
=> SectionIndex * 16 + ItemIndex;
}
27 changes: 12 additions & 15 deletions VirtualListView/VirtualListViewHandler.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -97,36 +97,33 @@ public bool IsItemSelected(int sectionIndex, int itemIndex)
return previousSelections.Contains(new ItemPosition(sectionIndex, itemIndex));
}

ItemPosition[] previousSelections = Array.Empty<ItemPosition>();
HashSet<ItemPosition> previousSelections = [];

public static void MapSelectedItems(VirtualListViewHandler handler, IVirtualListView virtualListView)
{
if (handler is null)
return;

var newSelections = virtualListView?.SelectedItems ?? Array.Empty<ItemPosition>();
ISet<ItemPosition> newSelections = virtualListView?.SelectedItems ?? new HashSet<ItemPosition>();

if (virtualListView.SelectionMode == SelectionMode.None)
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I have a small refactoring suggestion, as i wonder if this needs to be checked for null as well? I Mean when virtualListView is null, it throws a NullReferenceException.
So in the current state when we have a virtualListView of null we have a new HashSet on Line 107 but cannot continue, as it should throw an exception on Line 109/111

Suggested change
if (virtualListView.SelectionMode == SelectionMode.None)
if (virtualListView?.SelectionMode == SelectionMode.None)

newSelections = Array.Empty<ItemPosition>();
newSelections = new HashSet<ItemPosition>();
else if (virtualListView.SelectionMode == SelectionMode.Single && newSelections.Count > 1)
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I see the same problem here

Suggested change
else if (virtualListView.SelectionMode == SelectionMode.Single && newSelections.Count > 1)
else if (virtualListView?.SelectionMode == SelectionMode.Single && newSelections.Count > 1)

newSelections = newSelections.Take(1).ToArray();
newSelections = newSelections.Take(1).ToHashSet();

// First deselect any previously selected items that aren't in the new set
foreach (var itemPosition in handler.previousSelections)
var changed = new HashSet<ItemPosition>(handler.previousSelections);
changed.SymmetricExceptWith(newSelections);
foreach (var itemPosition in changed)
{
if (!newSelections.Contains(itemPosition))
if (handler.previousSelections.Contains(itemPosition))
// Deselect any previously selected items that aren't in the new set
handler.PlatformUpdateItemSelection(itemPosition, false);
}

// Set all the new state selected to true
foreach (var itemPosition in newSelections)
{
if (!handler.previousSelections.Contains(itemPosition))
else
// Set all the new state selected to true
handler.PlatformUpdateItemSelection(itemPosition, true);
}

// Keep track of the new state for next time it changes
handler.previousSelections = newSelections.ToArray();
handler.previousSelections = new HashSet<ItemPosition>(newSelections);
}

public static void MapIsHeaderVisible(VirtualListViewHandler handler, IVirtualListView virtualListView)
Expand Down