/// <summary>
/// Gets the actual item template size, using a non-databound materialized
/// view of the template.
/// </summary>
/// <param name="dataTemplate">A data template</param>
/// <returns>The actual size of the template</returns>
private CGSize GetTemplateSize(DataTemplate dataTemplate, NSString elementKind)
{
//TODO: this should take an available breadth
CGSize size;
// Cache the sizes to avoid creating new templates everytime.
if (!_templateCache.TryGetValue(dataTemplate ?? _nullDataTemplateKey, out size))
{
var container = CreateContainerForElementKind(elementKind);
// Force a null DataContext so the parent's value does not flow
// through when temporarily adding the container to Owner.XamlParent
container.SetValue(FrameworkElement.DataContextProperty, null);
Style style = null;
if (elementKind == NativeListViewBase.ListViewItemElementKind)
{
style = Owner.ItemContainerStyle;
}
else if (elementKind == NativeListViewBase.ListViewSectionHeaderElementKind)
{
style = Owner.GroupStyle?.HeaderContainerStyle;
}
if (style != null)
{
container.Style = style;
}
container.ContentTemplate = dataTemplate;
try
{
// Attach templated container to visual tree while measuring. This works around the bug that default Style is not
// applied until view is loaded.
Owner.XamlParent.AddSubview(BlockLayout);
BlockLayout.AddSubview(container);
// Measure with PositiveInfinity rather than MaxValue, since some views handle this better.
size = Owner.NativeLayout.Layouter.MeasureChild(container, new Size(double.PositiveInfinity, double.PositiveInfinity));
if ((size.Height > nfloat.MaxValue / 2 || size.Width > nfloat.MaxValue / 2) &&
this.Log().IsEnabled(LogLevel.Warning)
)
{
this.Log().LogWarning($"Infinite item size reported, this can crash {nameof(UICollectionView)}.");
}
}
finally
{
Owner.XamlParent.RemoveChild(BlockLayout);
BlockLayout.RemoveChild(container);
// Reset the DataContext for reuse.
container.ClearValue(FrameworkElement.DataContextProperty);
}
_templateCache[dataTemplate ?? _nullDataTemplateKey] = size;
}
return(size);
}
/// <summary>
/// Gets the actual item template size, using a non-databound materialized
/// view of the template.
/// </summary>
/// <param name="dataTemplate">A data template</param>
/// <returns>The actual size of the template</returns>
private CGSize GetTemplateSize(DataTemplate dataTemplate, NSString elementKind)
{
//TODO: this should take an available breadth
CGSize size;
// Cache the sizes to avoid creating new templates everytime.
if (!_templateCache.TryGetValue(dataTemplate ?? _nullDataTemplateKey, out size))
{
var container = CreateContainerForElementKind(elementKind);
Style style = null;
if (elementKind == NativeListViewBase.ListViewItemElementKind)
{
style = Owner.ItemContainerStyle;
}
else if (elementKind == NativeListViewBase.ListViewSectionHeaderElementKind)
{
style = Owner.GroupStyle?.HeaderContainerStyle;
}
if (style != null)
{
container.Style = style;
}
container.ContentTemplate = dataTemplate;
try
{
// Attach templated container to visual tree while measuring. This works around the bug that default Style is not
// applied until view is loaded.
Owner.XamlParent.AddSubview(BlockLayout);
BlockLayout.AddSubview(container);
size = Owner.NativeLayout.Layouter.MeasureChild(container, new Size(double.MaxValue, double.MaxValue));
if ((size.Height > nfloat.MaxValue / 2 || size.Width > nfloat.MaxValue / 2) &&
this.Log().IsEnabled(LogLevel.Warning)
)
{
this.Log().LogWarning($"Infinite item size reported, this can crash {nameof(UICollectionView)}.");
}
}
finally
{
Owner.XamlParent.RemoveChild(BlockLayout);
BlockLayout.RemoveChild(container);
}
_templateCache[dataTemplate ?? _nullDataTemplateKey] = size;
}
return(size);
}