public override void PrepareLayout()
{
base.PrepareLayout();
var sectionCount = CollectionView.NumberOfSections();
if (sectionCount == 0)
{
return;
}
// Reset Cache
_cachedAttributes.Clear();
_contentBounds = new CGRect(CGPoint.Empty, CollectionView.Bounds.Size);
var itemCount = CollectionView.NumberOfItemsInSection(0);
var currentIndex = 0;
var itemStyle = DetermineItemStyle(itemCount);
var lastFrame = CGRect.Empty;
var cvWidth = CollectionView.Bounds.Width;
var cvHeight = CollectionView.Bounds.Height;
while (currentIndex < itemCount)
{
CGRect segmentFrame;
var segmentRects = new List <CGRect>();
switch (itemStyle)
{
case MosaicStyle.FullWidth:
segmentFrame = new CGRect(0, lastFrame.GetMaxY() + 1, cvWidth, cvHeight);
segmentRects.Add(segmentFrame);
break;
case MosaicStyle.HalfWidth:
segmentFrame = new CGRect(0, lastFrame.GetMaxY() + 1, cvWidth, cvHeight / 2);
var slices = segmentFrame.DividedIntegral((nfloat)0.5, CGRectEdge.MinXEdge);
segmentRects.Add(slices["First"]);
segmentRects.Add(slices["Second"]);
break;
case MosaicStyle.TwoThirdsByOneThird:
segmentFrame = new CGRect(0, lastFrame.GetMaxY() + 1, cvWidth, cvHeight / 3);
var twoThirdsHorizontalSlices = segmentFrame.DividedIntegral((nfloat)(2.0 / 3.0), CGRectEdge.MinXEdge);
var twoThirdsVerticalSlices = segmentFrame.DividedIntegral((nfloat)0.5, CGRectEdge.MinYEdge);
segmentRects.Add(twoThirdsHorizontalSlices["First"]);
segmentRects.Add(twoThirdsVerticalSlices["First"]);
segmentRects.Add(twoThirdsVerticalSlices["Second"]);
break;
case MosaicStyle.OneThirdByTwoThirds:
segmentFrame = new CGRect(0, lastFrame.GetMaxY() + 1, cvWidth, cvHeight / 3);
var oneThirdHorizontalSlices = segmentFrame.DividedIntegral((nfloat)(1.0 / 3.0), CGRectEdge.MinXEdge);
var oneThirdVerticalSlices = segmentFrame.DividedIntegral((nfloat)0.5, CGRectEdge.MinYEdge);
segmentRects.Add(oneThirdVerticalSlices["First"]);
segmentRects.Add(oneThirdVerticalSlices["Second"]);
segmentRects.Add(oneThirdHorizontalSlices["Second"]);
break;
}
// cache attributes.
foreach (var rect in segmentRects)
{
var indexPath = NSIndexPath.FromRowSection(currentIndex, 0);
var attributes = UICollectionViewLayoutAttributes.CreateForCell(indexPath);
attributes.Frame = rect;
_cachedAttributes.Add(attributes);
_contentBounds = _contentBounds.UnionWith(lastFrame);
currentIndex++;
lastFrame = rect;
}
// determine style for next segment
switch (itemCount - currentIndex)
{
case 1:
itemStyle = MosaicStyle.FullWidth;
break;
case 2:
itemStyle = MosaicStyle.HalfWidth;
break;
default:
switch (itemStyle)
{
case MosaicStyle.FullWidth:
itemStyle = MosaicStyle.HalfWidth;
break;
case MosaicStyle.HalfWidth:
itemStyle = MosaicStyle.TwoThirdsByOneThird;
break;
case MosaicStyle.TwoThirdsByOneThird:
itemStyle = MosaicStyle.OneThirdByTwoThirds;
break;
case MosaicStyle.OneThirdByTwoThirds:
itemStyle = MosaicStyle.HalfWidth;
break;
}
break;
}
}
}
