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清理和优化了一些方法名
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@xtuzy
xtuzy committed Sep 14, 2023
1 parent fae204f commit f246475
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Showing 6 changed files with 208 additions and 311 deletions.
2 changes: 1 addition & 1 deletion DemoTest/Pages/DefaultTestPage.xaml.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -35,7 +35,7 @@ public DefaultTestPage()
VerticalScrollBarVisibility = ScrollBarVisibility.Always,
HeightExpansionFactor = OperatingSystem.IsIOS()? 0:0,
SelectionMode = SelectionMode.Multiple,
CanDrag = true,
//CanDrag = true,
};
tableView.ItemsLayout = new CollectionViewFlatListLayout(tableView)
{
Expand Down
136 changes: 78 additions & 58 deletions MauiUICollectionView/Layouts/CollectionViewFlatListLayout.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -28,16 +28,16 @@ protected override double MeasureItems(double top, Rect inRect, Rect visibleRect
isScrollingTo == false &&
!HasOperation)
{
//MeasureItemsWhenScroll(inRect, availablePreparedItems);
MeasureItems(top, inRect, availablePreparedItems, false);
Fill(inRect, AnalysisBaseline(top), availablePreparedItems, false);
}
else
{
MeasureItems(top, inRect, availablePreparedItems);
Fill(inRect, AnalysisBaseline(top), availablePreparedItems, true);

if (isScrollingTo)
isScrollingTo = false;
if (BaseLineItemUsually != null)
BaseLineItemUsually = null;
if (ItemLayoutBaseline != null)
ItemLayoutBaseline = null;
}

// store some bounds
Expand Down Expand Up @@ -90,22 +90,20 @@ protected override double MeasureItems(double top, Rect inRect, Rect visibleRect
/// <summary>
/// When not touch scrolling, we use it to remeasure all prepared items.
/// </summary>
/// <param name="inRect"></param>
/// <param name="top"></param>
/// <param name="availablePreparedItems"></param>
protected virtual void MeasureItems(double top, Rect inRect, Dictionary<NSIndexPath, MAUICollectionViewViewHolder> availablePreparedItems, bool isRemeasureAll = true)
protected virtual LayoutInfor AnalysisBaseline(double top)
{
if (BaseLineItemUsually != null)// use specify baseline to layout
if (ItemLayoutBaseline != null)// use specify baseline to layout
{
OnLayoutChildren(inRect, BaseLineItemUsually.Copy(), availablePreparedItems, isRemeasureAll);
return ItemLayoutBaseline.Copy();
}
else if (OldPreparedItems.StartItem != null)// use last layout item as baseline to layout
{
OnLayoutChildren(inRect, new LayoutInfor()
return new LayoutInfor()
{
StartItem = OldPreparedItems.StartItem,
StartBounds = OldPreparedItems.StartBounds
}, availablePreparedItems, isRemeasureAll);
};
}
else //use header's bottom as baseline to layout, this will be called when start a new collectionview or error(because fast scroll, scrollto, drag scrollbar)
{
Expand All @@ -118,31 +116,30 @@ protected virtual void MeasureItems(double top, Rect inRect, Dictionary<NSIndexP
var rect = StartBoundsCache[i];
if (rect.Contains(0, CollectionView.ScrollY))
{
OnLayoutChildren(inRect, new LayoutInfor()
return new LayoutInfor()
{
StartItem = NSIndexPath.FromRowSection(i, 0),
StartBounds = new Rect(0, rect.Top, 0, 0),
}, availablePreparedItems, isRemeasureAll);
};
}
}
}
else//estimate scrolly to fix
{
OnLayoutChildren(inRect, new LayoutInfor()
return new LayoutInfor()
{
StartItem = EstimateItem(0, CollectionView.ScrollY),
StartItem = ItemAtPoint(new Point(0, CollectionView.ScrollY)),
StartBounds = new Rect(0, CollectionView.ScrollY, 0, 0),
}, availablePreparedItems, isRemeasureAll);
};
}
}
else// when header is visible, use first item

// if we can't easy solve error, try use first item
return new LayoutInfor()
{
OnLayoutChildren(inRect, new LayoutInfor()
{
StartItem = NSIndexPath.FromRowSection(0, 0),
StartBounds = new Rect(0, top, 0, 0),
}, availablePreparedItems, isRemeasureAll);
}
StartItem = NSIndexPath.FromRowSection(0, 0),
StartBounds = new Rect(0, top, 0, 0),
};
}
}

Expand All @@ -155,42 +152,14 @@ protected virtual double EstimateAverageHeight()
return (StartBoundsCache.Last().Bottom - StartBoundsCache.First().Top) / StartBoundsCache.Count;
}

/// <summary>
/// Estimate the item displayed when scrolling to a certain position.
/// </summary>
/// <param name="y"></param>
/// <returns></returns>
protected virtual NSIndexPath EstimateItem(double x, double y)
{
var firstItemBounds = StartBoundsCache.First();
double averageHeight = EstimateAverageHeight();

var numberOfSections = CollectionView.NumberOfSections();
double allHeight = 0;
for (var section = 0; section < numberOfSections; section++)
{
var rowsInSection = CollectionView.NumberOfItemsInSection(section);
if (y - firstItemBounds.Top < allHeight + rowsInSection * averageHeight)
{
return NSIndexPath.FromRowSection((int)((y - firstItemBounds.Top - allHeight) / averageHeight), section);
}
else
{
allHeight += rowsInSection * averageHeight;
}
}
//maybe scrolly is very big
return NSIndexPath.FromRowSection(CollectionView.NumberOfItemsInSection(numberOfSections - 1), numberOfSections - 1);
}

/// <summary>
/// Arrange items from above or below to fill a given rectangle.
/// </summary>
/// <param name="inRect"></param>
/// <param name="baselineInfor">according to it to layout other items</param>
/// <param name="availableCells"></param>
/// <exception cref="NotImplementedException"></exception>
protected virtual void OnLayoutChildren(Rect inRect, LayoutInfor baselineInfor, Dictionary<NSIndexPath, MAUICollectionViewViewHolder> availableCells, bool isRemeasureAll = true)
protected virtual void Fill(Rect inRect, LayoutInfor baselineInfor, Dictionary<NSIndexPath, MAUICollectionViewViewHolder> availableCells, bool isRemeasureAll = true)
{
/*
* from top to bottom, means we have a top value of item, we base on it to calculate bounds of items below.
Expand Down Expand Up @@ -393,7 +362,7 @@ protected virtual void ScrollToItem(NSIndexPath targetIndexPath)
if (targetIndexPath > lastPreparedItem.Key)//The target item is at the bottom of the visible area, laid out from the bottom up.
{
itemsOffset += CollectionView.ItemCountInRange(lastPreparedItem.Key, targetIndexPath) * lastPreparedItem.Value.ItemBounds.Height;
BaseLineItemUsually = new LayoutInfor()
ItemLayoutBaseline = new LayoutInfor()
{
EndBounds = new Rect(0, 0, 0, CollectionView.ScrollY + itemsOffset + CollectionView.Bounds.Height), //set this item at bottom of visible area.
EndItem = targetIndexPath
Expand All @@ -406,7 +375,7 @@ protected virtual void ScrollToItem(NSIndexPath targetIndexPath)
var itemsCountFromTargetToFirstPrepared = CollectionView.ItemCountInRange(targetIndexPath, firstPreparedItem.Key) + 1;
var itemsCountFromFirstToFirstPrepared = CollectionView.ItemCountInRange(NSIndexPath.FromRowSection(0, 0), firstPreparedItem.Key) + 1;
var distanceFromTargetToFirstPrepared = (firstPreparedItem.Value.ItemBounds.Top - StartBoundsCache[0].Top) * itemsCountFromTargetToFirstPrepared / itemsCountFromFirstToFirstPrepared + (CollectionView.ScrollY - firstPreparedItem.Value.ItemBounds.Top);
BaseLineItemUsually = new LayoutInfor()
ItemLayoutBaseline = new LayoutInfor()
{
StartBounds = new Rect(0, CollectionView.ScrollY - distanceFromTargetToFirstPrepared, 0, 0),
StartItem = targetIndexPath
Expand Down Expand Up @@ -476,7 +445,7 @@ void FitBoundsWhenCloseHeader(LayoutInfor visibleItems)
var targetBounds = StartBoundsCache[visibleFirst.Row];
if (CollectionView.PreparedItems[visibleFirst].ItemBounds != targetBounds)
{
BaseLineItemUsually = new LayoutInfor()
ItemLayoutBaseline = new LayoutInfor()
{
StartBounds = new Rect(0, targetBounds.Top, 0, 0),
StartItem = visibleFirst
Expand All @@ -489,7 +458,7 @@ void FitBoundsWhenCloseHeader(LayoutInfor visibleItems)
{
var targetTop = CollectionView.PreparedItems[visibleFirst].ItemBounds.Bottom + CollectionView.ItemCountInRange(lastCache, visibleFirst) * EstimateAverageHeight();

BaseLineItemUsually = new LayoutInfor()
ItemLayoutBaseline = new LayoutInfor()
{
StartBounds = new Rect(0, targetTop, 0, 0),
StartItem = visibleFirst
Expand All @@ -508,7 +477,7 @@ void FitBoundsWhenCloseHeader(LayoutInfor visibleItems)
if (firstItemRect.Top > StartBoundsCache[0].Top && //There is space
CollectionView.ScrollY < (firstItemRect.Bottom - firstItemRect.Height * 4 / 5))//when close to first item top
{
BaseLineItemUsually = new LayoutInfor()
ItemLayoutBaseline = new LayoutInfor()
{
StartBounds = new Rect(0, StartBoundsCache[0].Top, 0, 0),
StartItem = firstItem
Expand Down Expand Up @@ -594,6 +563,57 @@ public override Rect RectForItem(NSIndexPath indexPath)
return rect;
}

#region ItemAtPoint

public override NSIndexPath ItemAtPoint(Point point, bool baseOnContent = true)
{
if (!baseOnContent)
{
var contentOffset = CollectionView.ScrollY;
point.Y = point.Y + contentOffset;//convert to base on content
}

foreach (var item in CollectionView.PreparedItems)
{
if (item.Value.ItemBounds.Contains(point))
{
return item.Key;
}
}

return EstimateItem(point.X, point.Y);
}

/// <summary>
/// Estimate the item displayed when scrolling to a certain position.
/// </summary>
/// <param name="y"></param>
/// <returns></returns>
NSIndexPath EstimateItem(double x, double y)
{
var firstItemBounds = StartBoundsCache.First();
double averageHeight = EstimateAverageHeight();

var numberOfSections = CollectionView.NumberOfSections();
double allHeight = 0;
for (var section = 0; section < numberOfSections; section++)
{
var rowsInSection = CollectionView.NumberOfItemsInSection(section);
if (y - firstItemBounds.Top < allHeight + rowsInSection * averageHeight)
{
return NSIndexPath.FromRowSection((int)((y - firstItemBounds.Top - allHeight) / averageHeight), section);
}
else
{
allHeight += rowsInSection * averageHeight;
}
}
//maybe scrolly is very big
return NSIndexPath.FromRowSection(CollectionView.NumberOfItemsInSection(numberOfSections - 1), numberOfSections - 1);
}

#endregion

#endregion
}
}
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