protected virtual void BoundsSizeChanged() { //We are changing orientation and we need to tell our layout //to update based on new size constrains ItemsViewLayout.ConstrainTo(CollectionView.Bounds.Size); //We call ReloadData so our VisibleCells also update their size CollectionView.ReloadData(); }
void CheckForEmptySource() { var wasEmpty = _isEmpty; _isEmpty = ItemsSource.ItemCount == 0; if (wasEmpty != _isEmpty) { UpdateEmptyViewVisibility(_isEmpty); } if (wasEmpty && !_isEmpty) { // If we're going from empty to having stuff, it's possible that we've never actually measured // a prototype cell and our itemSize or estimatedItemSize are wrong/unset // So trigger a constraint update; if we need a measurement, that will make it happen ItemsViewLayout.ConstrainTo(CollectionView.Bounds.Size); } }
public override void ViewWillLayoutSubviews() { base.ViewWillLayoutSubviews(); // We can't set this constraint up on ViewDidLoad, because Forms does other stuff that resizes the view // and we end up with massive layout errors. And View[Will/Did]Appear do not fire for this controller // reliably. So until one of those options is cleared up, we set this flag so that the initial constraints // are set up the first time this method is called. if (!_initialConstraintsSet) { _size = CollectionView.Bounds.Size; ItemsViewLayout.ConstrainTo(_size); UpdateEmptyView(); _initialConstraintsSet = true; } else { LayoutEmptyView(); } }
public void UpdateLayout(ItemsViewLayout newLayout) { // Ignore calls to this method if the new layout is the same as the old one if (CollectionView.CollectionViewLayout == newLayout) { return; } ItemsViewLayout = newLayout; ItemsViewLayout.GetPrototype = GetPrototype; Delegator = CreateDelegator(); CollectionView.Delegate = Delegator; // Make sure the new layout is sized properly ItemsViewLayout.ConstrainTo(CollectionView.Bounds.Size); CollectionView.SetCollectionViewLayout(ItemsViewLayout, false); // Reload the data so the currently visible cells get laid out according to the new layout CollectionView.ReloadData(); }