How to implement UICollectionView - XAMARIN.IOS - xamarin.ios

Question

I'm trying to use UICollectionView but I can't find any samples that I can take advantage of. I needed the UICollectionView by code (without using swift/storyboard/forms). Could you give me a really simple example? For example 2 lines with 2 columns please? Basic stuff just to try to understand how I can implement it.
Thank you

Answer 1

You can refer to Collection Views in Xamarin.iOS doc to check how to use Collection View with Code .And here I will show a sample code to explain how to implement it .
Could you give me a really simple example? For example 2 lines with 2 columns please?
First , need to create a GridLayout :
public class GridLayout : UICollectionViewFlowLayout
{
public GridLayout ()
{
}
public override bool ShouldInvalidateLayoutForBoundsChange (CGRect newBounds)
{
return true;
}
public override UICollectionViewLayoutAttributes LayoutAttributesForItem (NSIndexPath path)
{
return base.LayoutAttributesForItem (path);
}
public override UICollectionViewLayoutAttributes[] LayoutAttributesForElementsInRect (CGRect rect)
{
return base.LayoutAttributesForElementsInRect (rect);
}
}
Then you can init the Collection View in ViewDidLoad :
static NSString animalCellId = new NSString("AnimalCell");
List<IAnimal> animals;
animals = new List<IAnimal>();
for (int i = 0; i < 2; i++)
{
animals.Add(new Monkey());
}
// Perform any additional setup after loading the view, typically from a nib.
UICollectionView collectionView = new UICollectionView(new CGRect(0, 0, UIScreen.MainScreen.Bounds.Size.Width, 300), new GridLayout());
collectionView.RegisterClassForCell(typeof(AnimalCell), animalCellId);
collectionView.BackgroundColor = UIColor.Blue;
collectionView.DataSource = new MyCollectionViewDataDelegate(animals);
View.AddSubview(collectionView);
Here you also need to creat a Custom Cell for your needs , this can be modified by yourself :
public class AnimalCell : UICollectionViewCell
{
UIImageView imageView;
[Export("initWithFrame:")]
public AnimalCell(CGRect frame) : base(frame)
{
BackgroundView = new UIView { BackgroundColor = UIColor.Orange };
SelectedBackgroundView = new UIView { BackgroundColor = UIColor.Green };
ContentView.Layer.BorderColor = UIColor.LightGray.CGColor;
ContentView.Layer.BorderWidth = 2.0f;
ContentView.BackgroundColor = UIColor.White;
ContentView.Transform = CGAffineTransform.MakeScale(0.8f, 0.8f);
imageView = new UIImageView(UIImage.FromBundle("placeholder.png"));
imageView.Center = ContentView.Center;
imageView.Transform = CGAffineTransform.MakeScale(0.7f, 0.7f);
ContentView.AddSubview(imageView);
}
public UIImage Image
{
set
{
imageView.Image = value;
}
}
[Export("custom")]
void Custom()
{
// Put all your custom menu behavior code here
Console.WriteLine("custom in the cell");
}
public override bool CanPerform(Selector action, NSObject withSender)
{
if (action == new Selector("custom"))
return true;
else
return false;
}
}
The MyCollectionViewDataDelegate also need to be created:
public class MyCollectionViewDataDelegate : UICollectionViewDataSource
{
private List animals;
public MyCollectionViewDataDelegate(List<IAnimal> animals)
{
this.animals = animals;
}
public override nint NumberOfSections(UICollectionView collectionView)
{
return 2;
}
public override nint GetItemsCount(UICollectionView collectionView, nint section)
{
return animals.Count;
}
public override UICollectionViewCell GetCell(UICollectionView collectionView, NSIndexPath indexPath)
{
var animalCell = (AnimalCell)collectionView.DequeueReusableCell(animalCellId, indexPath);
var animal = animals[indexPath.Row];
animalCell.Image = animal.Image;
return animalCell;
}
}
You can find that animalCell should be registed when init Collection View .
Then effect :
This is the sample link for reference .