private (View itemContainer, Rectangle childLocation) GetItemContainerLocationByindex(double width, int index, double yOffset, ref bool doMeasureInvalidation)
{
View itemContainer = null;
if (ItemsGenerator.HasItemViewGenerated(index))
{
itemContainer = ItemsGenerator.GetItemViewFromIndex(index);
}
else
{
itemContainer = ItemsGenerator.GenerateItemView(index);
}
// Add child to layout because then style will activate
if (Children.Contains(itemContainer) == false)
{
Children.Add(itemContainer);
doMeasureInvalidation = true;
}
Rectangle childLocation = new Rectangle();
if (IsRecycleEnabled)
{
SizeRequest itemSize = itemContainer.Measure(width, double.PositiveInfinity, MeasureFlags.IncludeMargins);
childLocation = new Rectangle(0, yOffset, width, itemSize.Request.Height);
if (_locations.ContainsKey(itemContainer))
{
_locations[itemContainer] = childLocation;
}
else
{
_locations.Add(itemContainer, childLocation);
}
}
else if (_locations.TryGetValue(itemContainer, out childLocation) == false)
{
SizeRequest itemSize = itemContainer.Measure(width, double.PositiveInfinity, MeasureFlags.IncludeMargins);
childLocation = new Rectangle(0, yOffset, width, itemSize.Request.Height);
_locations.Add(itemContainer, childLocation);
}
else
{
childLocation = new Rectangle(0, yOffset, width, _locations[itemContainer].Height);
_locations[itemContainer] = childLocation;
}
return(itemContainer, childLocation);
}
/// <summary>
/// Close all submenus
/// </summary>
public void CloseSubMenus()
{
for (int i = 0; i < ItemsGenerator.TotalItemsCount; i++)
{
if (ItemsGenerator.HasItemViewGenerated(i))
{
View itemContainer = ItemsGenerator.GetItemViewFromIndex(i);
if (itemContainer is MenuButton menuButton)
{
menuButton.IsOpen = false;
}
}
}
}
protected override void OnSelectionModeChanged(SelectionModes oldValue, SelectionModes newValue)
{
base.OnSelectionModeChanged(oldValue, newValue);
for (int i = 0; i < ItemsGenerator.TotalItemsCount; i++)
{
if (ItemsGenerator.HasItemViewGenerated(i))
{
View item = ItemsGenerator.GetItemViewFromIndex(i);
InitializeItem(item);
if (_leftPadding != null)
{
SetLeftPadding(item, _leftPadding.Value);
}
}
}
}
/// <summary>
/// Do filter with search key string
/// </summary>
public void DoFilter(string searchKey)
{
for (int i = 0; i < ItemsGenerator.TotalItemsCount; i++)
{
if (ItemsGenerator.HasItemViewGenerated(i))
{
View itemContainer = ItemsGenerator.GetItemViewFromIndex(i);
if ((itemContainer is IFilter filterItem && filterItem.IsFiltered(searchKey) == true) ||
(itemContainer.BindingContext is IFilter filterItemModel && filterItemModel.IsFiltered(searchKey) == true))
{
itemContainer.IsVisible = false;
}
else
{
itemContainer.IsVisible = true;
}
}
}
/// <summary>
/// Set items left padding
/// </summary>
/// <param name="padding"></param>
public void SetItemsLeftPadding(double padding)
{
bool wasChanged = _leftPadding != null;
_leftPadding = padding;
for (int i = 0; i < ItemsGenerator.TotalItemsCount; i++)
{
if (ItemsGenerator.HasItemViewGenerated(i))
{
View item = ItemsGenerator.GetItemViewFromIndex(i);
if (_leftPadding != null)
{
SetLeftPadding(item, padding);
}
else if (wasChanged && item is Button button)
{
button.ClearValue(Button.PaddingProperty);
}
}
}
}
/// <summary>
/// Update visible items based on items measured or estimated size and scroll info.
/// </summary>
private void UpdateVisibleItems(double width, double scrollDelta)
{
_ignoreInvalidation = true;
bool doMeasureInvalidation = false;
double yOffset = _firstVisibleItemOffset;
double firstVisibleItemHeight = 0;
_visibleItems.Clear();
_currentStickyElement = null;
_nextStickyElement = null;
if (scrollDelta <= 0)
{
for (int i = _firstVisibleItemIndex; i < ItemsGenerator.TotalItemsCount; i++)
{
(View itemContainer, Rectangle childLocation) = GetItemContainerLocationByindex(width, i, yOffset, ref doMeasureInvalidation);
// Set current sticky element
if (GetIsSticky(itemContainer))
{
_currentStickyElement = itemContainer;
}
_firstVisibleItemIndex = i;
yOffset += childLocation.Height;
if (yOffset >= VerticalOffset - _viewportOverflowLenght)
{
_visibleItems.Add(itemContainer);
if (Children.Contains(itemContainer) == false)
{
Children.Add(itemContainer);
doMeasureInvalidation = true;
}
ItemsGenerator.SetRealized(i);
LayoutChild(itemContainer, childLocation);
firstVisibleItemHeight = childLocation.Height;
break;
}
// Remove container from children if not visible
else if (Children.Contains(itemContainer) && itemContainer != _currentStickyElement)
{
if (IsRecycleEnabled == false)
{
Children.Remove(itemContainer);
}
ItemsGenerator.SetVirtualized(i);
}
_firstVisibleItemOffset = yOffset;
}
}
else
{
for (int i = _firstVisibleItemIndex; i >= 0; i--)
{
(View itemContainer, Rectangle childLocation) = GetItemContainerLocationByindex(width, i, yOffset, ref doMeasureInvalidation);
// Set current sticky element
if (GetIsSticky(itemContainer))
{
_currentStickyElement = itemContainer;
}
_firstVisibleItemIndex = i;
yOffset -= childLocation.Height;
if (yOffset + childLocation.Height <= VerticalOffset - _viewportOverflowLenght || i == 0)
{
_visibleItems.Add(itemContainer);
if (Children.Contains(itemContainer) == false)
{
Children.Add(itemContainer);
doMeasureInvalidation = true;
}
ItemsGenerator.SetRealized(i);
LayoutChild(itemContainer, childLocation);
firstVisibleItemHeight = childLocation.Height;
break;
}
// Remove container from children if not visible
else if (Children.Contains(itemContainer) && itemContainer != _currentStickyElement)
{
if (IsRecycleEnabled == false)
{
Children.Remove(itemContainer);
}
ItemsGenerator.SetVirtualized(i);
}
_firstVisibleItemOffset = yOffset;
}
_firstVisibleItemOffset = Math.Max(0, _firstVisibleItemOffset);
}
int lastVisibleItemIndex = _firstVisibleItemIndex;
yOffset = _firstVisibleItemOffset + firstVisibleItemHeight;
// Set items visible until viewport is ended
for (int i = _firstVisibleItemIndex + 1; i < ItemsGenerator.TotalItemsCount; i++)
{
if (yOffset >= VerticalOffset + ViewportSize.Height + _viewportOverflowLenght)
{
break;
}
(View itemContainer, Rectangle childLocation) = GetItemContainerLocationByindex(width, i, yOffset, ref doMeasureInvalidation);
// Get next sticky elements
if (_nextStickyElement == null && _currentStickyElement != null && itemContainer != _currentStickyElement && GetIsSticky(itemContainer))
{
_nextStickyElement = itemContainer;
}
LayoutChild(itemContainer, childLocation);
_visibleItems.Add(itemContainer);
lastVisibleItemIndex = i;
yOffset += childLocation.Height;
ItemsGenerator.SetRealized(i);
}
// Remove items after viewport
for (int i = lastVisibleItemIndex + 1; i < ItemsGenerator.TotalItemsCount; i++)
{
if (ItemsGenerator.HasItemViewGenerated(i))
{
View itemContainer = ItemsGenerator.GetItemViewFromIndex(i);
if (Children.Contains(itemContainer) && IsRecycleEnabled == false)
{
Children.Remove(itemContainer);
}
ItemsGenerator.SetVirtualized(i);
}
else
{
break;
}
}
if (_currentStickyElement != null)
{
RaiseChild(_currentStickyElement);
}
_ignoreInvalidation = false;
if (doMeasureInvalidation && scrollDelta.Equals(0))
{
InvalidateMeasure();
InvalidateLayout();
}
}
