public void PrepareCellForLayout(ItemsViewCell cell)
{
if (EstimatedItemSize == CGSize.Empty)
{
cell.ConstrainTo(ItemSize);
}
else
{
cell.ConstrainTo(ConstrainedDimension);
}
}
protected void DetermineCellSize()
{
if (GetPrototype == null)
{
return;
}
// We set the EstimatedItemSize here for two reasons:
// 1. If we don't set it, iOS versions below 10 will crash
// 2. If GetPrototype() cannot return a cell because the items source is empty, we need to have
// an estimate set so that when a cell _does_ become available (i.e., when the items source
// has at least one item), Autolayout will kick in for the first cell and size it correctly
// If GetPrototype() _can_ return a cell, this estimate will be updated once that cell is measured
if (EstimatedItemSize == CGSize.Empty)
{
EstimatedItemSize = new CGSize(1, 1);
}
ItemsViewCell prototype = null;
if (CollectionView?.VisibleCells.Length > 0)
{
prototype = CollectionView.VisibleCells[0] as ItemsViewCell;
}
if (prototype == null)
{
prototype = GetPrototype() as ItemsViewCell;
}
if (prototype == null)
{
return;
}
// Constrain and measure the prototype cell
prototype.ConstrainTo(ConstrainedDimension);
var measure = prototype.Measure();
if (ItemSizingStrategy == ItemSizingStrategy.MeasureFirstItem)
{
// This is the size we'll give all of our cells from here on out
ItemSize = measure;
// Make sure autolayout is disabled
EstimatedItemSize = CGSize.Empty;
}
else
{
// Autolayout is now enabled, and this is the size used to guess scrollbar size and progress
EstimatedItemSize = measure;
}
}
