How to insert new cell at first element in UICollectionView in Xamarin? - xamarin

Question

I want to make horizontal collection and add new cell at the first position.
I make custom UICollectionViewFlowLayout and override
LayoutAttributesForElementsInRect like this (to see reverse order of items):
public override UICollectionViewLayoutAttributes[] LayoutAttributesForElementsInRect(CGRect rect)
{
var attributes = new UICollectionViewLayoutAttributes[cellCount];
NSIndexPath indexPath;
// Setting first position
int shift = 25, reverseXCenter;
for (int i = 0; i < cellCount; i++)
{
indexPath = NSIndexPath.FromItemSection(i, 0);
attributes[i] = LayoutAttributesForItem(indexPath);
// We have to make opposite order
reverseXCenter = (cellCount -1 - i) * 50;
attributes[i].Center = new CGPoint(reverseXCenter + shift, attributes[i].Center.Y);
}
return attributes;
}
I think is bad solution, because when I have more than 5 cells, the displayed collection is filled and I can't scroll.
I had debugger in GetOrCreateCellFor in CollectionViewSource
and indexPath.Item's had value for example (10,9,8,7,6...), where 10 is the last I added.
Maybe is another way to do this, or just I miss something?

Answer 1

Ok I am gonna help you out with a flow .
Suppose you are in a ViewController called "A" which will present a controller ViewController called "B"
Inside A use this function to push B
Public void PushNewHorizontalCollectionController(){
using (var vc =
new B(this.PageViewControllerLayout(), indexPath))
{
this.controller.PushViewController(pageViewController, true);
}
}
public UICollectionViewFlowLayout PageViewControllerLayout()
{
var flowLayout = new UICollectionViewFlowLayout();
var itemSize = this.controller.NavigationBarHidden ? new CGSize(Constants.ScreenWidth, Constants.ScreenHeight + 20) : new CGSize(Constants.ScreenWidth, Constants.ScreenHeight - Constants.NavigationHeaderAndStatusbarHeight);
flowLayout.ItemSize = itemSize;
flowLayout.MinimumLineSpacing = 0;
flowLayout.MinimumInteritemSpacing = 0;
flowLayout.ScrollDirection = UICollectionViewScrollDirection.Horizontal;
return flowLayout;
}
Here itemSize is CGSize which u can assign what size you can ignore my constants which are self explainable .
Inside B your constructor should look like this .
public HorizontalViewController(UICollectionViewLayout layout, NSIndexPath indexpath) : base(layout)
{
Do your initialisation like registering UICollectionViewCell class nibs for use with this Controller
}
Handling real requirement from comment .
You wanna add something always as 1st element in collectionView ,Go to this method which should look like below
public override UICollectionViewCell GetCell(UICollectionView collectionView, NSIndexPath indexPath)
{
Console.WriteLine("getcellHori");
var isQuoteType = Photo.PhotoCollection[(int)indexPath.Item].Type;
if (isQuoteType == 3 || isQuoteType == 4)
{
var item = Photo.PhotoCollection[(int)indexPath.Item];
var cell = (HorizontalviewForQuoteType)collectionView.DequeueReusableCell("HorizontalviewForQuoteType", indexPath);
cell.PopulateCell(item.Caption,item.TextLabel,item.Likes,item.TimeLabel,item.Id);
HorizontalviewForQuoteType.pullAction = (offset) =>
{
this.pullOffset = offset;
this.NavigationController.PopViewController(true);
};
cell.SetNeedsLayout();
return cell;
}
Here you this line
var item = Photo.PhotoCollection[(int)indexPath.Item];
this is the data source , so whenever you adding something at index first and everything will be solved .