public override void LayoutSubviews()
{
base.LayoutSubviews();
if (_previousFrame != Frame)
{
UpdateCellSize();
UpdateGroupHeaderWidth();
ViewLayout.InvalidateLayout();
}
_previousFrame = Frame;
}
protected override void OnElementPropertyChanged(object sender, PropertyChangedEventArgs e)
{
base.OnElementPropertyChanged(sender, e);
if (e.PropertyName == GridCollectionView.GroupHeaderHeightProperty.PropertyName)
{
UpdateGroupHeaderHeight();
ViewLayout.InvalidateLayout();
}
else if (e.PropertyName == GridCollectionView.GridTypeProperty.PropertyName ||
e.PropertyName == GridCollectionView.PortraitColumnsProperty.PropertyName ||
e.PropertyName == GridCollectionView.LandscapeColumnsProperty.PropertyName ||
e.PropertyName == GridCollectionView.ColumnSpacingProperty.PropertyName ||
e.PropertyName == GridCollectionView.ColumnHeightProperty.PropertyName ||
e.PropertyName == GridCollectionView.SpacingTypeProperty.PropertyName ||
e.PropertyName == GridCollectionView.AdditionalHeightProperty.PropertyName ||
e.PropertyName == CollectionView.GroupFirstSpacingProperty.PropertyName ||
e.PropertyName == CollectionView.GroupLastSpacingProperty.PropertyName ||
e.PropertyName == GridCollectionView.BothSidesMarginProperty.PropertyName)
{
UpdateGridType();
InvalidateLayout();
}
else if (e.PropertyName == GridCollectionView.RowSpacingProperty.PropertyName)
{
UpdateRowSpacing();
ViewLayout.InvalidateLayout();
}
else if (e.PropertyName == GridCollectionView.ColumnWidthProperty.PropertyName)
{
if (_gridCollectionView.GridType != GridType.UniformGrid)
{
UpdateGridType();
InvalidateLayout();
}
}
else if (e.PropertyName == ListView.IsPullToRefreshEnabledProperty.PropertyName)
{
UpdatePullToRefreshEnabled();
}
else if (e.PropertyName == GridCollectionView.PullToRefreshColorProperty.PropertyName)
{
UpdatePullToRefreshColor();
}
else if (e.PropertyName == Xamarin.Forms.ListView.IsRefreshingProperty.PropertyName)
{
UpdateIsRefreshing();
}
else if (e.PropertyName == GridCollectionView.IsGroupHeaderStickyProperty.PropertyName)
{
UpdateIsSticky();
InvalidateLayout();
}
}
void InvalidateLayout()
{
if (!_gridCollectionView.IsGroupingEnabled)
{
ViewLayout.InvalidateLayout();
return;
}
// HACK: When IsGroupingEnabled is true and changing such layout size as the item size and the spacing size,
// a header cell content is sometimes not reflected or broken layout.
// By reloading with a bit delay after scrolling to Top, this issue can be avoided.
Control.SetContentOffset(CGPoint.Empty, false);
DispatchQueue.MainQueue.DispatchAfter(new DispatchTime(DispatchTime.Now, TimeSpan.FromMilliseconds(150)), () =>
{
Control.ReloadData();
ViewLayout.InvalidateLayout();
});
}