Add items in collection view when scrolled in Xamarin IOS - xamarin

Question

I want to add new items to collection view when user scrolled the view.
I am able to add the items successful, but the scroll bar moved to top.
Please find my below code.
ViewControll Code:
public partial class ViewController : UIViewController
{
UIWindow window;
UICollectionViewController simpleCollectionViewController;
UICollectionViewFlowLayout flowLayout;
UIScrollView viewColle = new UIScrollView( new CGRect(0,100,UIScreen.MainScreen.Bounds.Width, 500));
int count = 2;
protected ViewController(IntPtr handle) : base(handle)
{
// Note: this .ctor should not contain any initialization logic.
}
public override void ViewDidLoad()
{
base.ViewDidLoad();
viewColle.BackgroundColor = UIColor.Green;
// Perform any additional setup after loading the view, typically from a nib.
// Flow Layout
flowLayout = new UICollectionViewFlowLayout () {
HeaderReferenceSize = new CGSize (0, 0),
SectionInset = new UIEdgeInsets (0, 0, 0, 0),
ScrollDirection = UICollectionViewScrollDirection.Vertical,
MinimumInteritemSpacing = 5, // minimum spacing between cells
MinimumLineSpacing = 5 // minimum spacing between rows if ScrollDirection is Vertical or between columns if Horizontal
};
simpleCollectionViewController = new MyCollectionViewController (flowLayout,count);
simpleCollectionViewController.CollectionView.ContentInset = new UIEdgeInsets (0, 0, 0, 0);
UIButton btnClick = new UIButton()
{
Frame = new CoreGraphics.CGRect(0,0,UIScreen.MainScreen.Bounds.Width,50),
BackgroundColor = UIColor.Gray
};
btnClick.SetTitle("Click", UIControlState.Normal);
btnClick.TouchUpInside += (sender, e) => {
window = new UIWindow(UIScreen.MainScreen.Bounds);
count++;
//var nav = new UINavigationController(simpleCollectionViewController);
//window.RootViewController = nav;
//window.MakeKeyAndVisible();
if (count > 3)
count = count / 3;
if (count == 1)
{
simpleCollectionViewController = new ListViewController (flowLayout,count,2);
simpleCollectionViewController.CollectionView.ContentInset = new UIEdgeInsets (0, 0, 0, 0);
viewColle.AddSubview(simpleCollectionViewController.View);
}
else if (count == 2)
{
simpleCollectionViewController = new MyCollectionViewController (flowLayout,count);
simpleCollectionViewController.CollectionView.ContentInset = new UIEdgeInsets (0, 0, 0, 0);
viewColle.AddSubview(simpleCollectionViewController.View);
}
else if (count == 3)
{
simpleCollectionViewController = new DetailViewController (flowLayout,1);
simpleCollectionViewController.CollectionView.ContentInset = new UIEdgeInsets (0, 0, 0, 0);
viewColle.AddSubview(simpleCollectionViewController.View);
}
//viewColle.Frame = new CGRect(0, 100, UIScreen.MainScreen.Bounds.Width, 500);
nfloat height0 = 0;
CGRect contentRect0 = new CGRect();
foreach (UIView view in viewColle.Subviews) {
height0 += view.Bounds.Height;
}
contentRect0.Size = new CGSize(View.Bounds.Width, height0 );
viewColle.ContentSize = contentRect0.Size;
//viewColle.ContentSize = new CGSize(simpleCollectionViewController.View.Bounds.Width, 2000);
View.AddSubview(btnClick);
View.AddSubview(viewColle);
};
viewColle.AddSubview(simpleCollectionViewController.View);
//viewColle.Frame = new CGRect(0, 100, UIScreen.MainScreen.Bounds.Width, 500);
nfloat height1 = 0;
CGRect contentRect1 = new CGRect();
foreach (UIView view in viewColle.Subviews) {
height1 += view.Bounds.Height;
}
contentRect1.Size = new CGSize(View.Bounds.Width, height1 );
viewColle.ContentSize = contentRect1.Size;
CGRect contentRect = new CGRect();
foreach (UIView view in viewColle.Subviews) {
contentRect = view.Frame;
}
viewColle.ContentSize = contentRect.Size;
//viewColle.ContentSize = new CGSize(simpleCollectionViewController.View.Bounds.Width, 2000);
View.AddSubview(btnClick);
View.AddSubview(viewColle);
viewColle.Scrolled += (sender, e) => {
UIAlertView alert = new UIAlertView("Scrolled Alert", "Scroller "+ count.ToString(), null, "Cancel", null);
alert.Show();
if (count > 3)
count = count / 3;
if (count == 1)
{
simpleCollectionViewController = new ListViewController (flowLayout,count,10);
simpleCollectionViewController.CollectionView.ContentInset = new UIEdgeInsets (0, 0, 0, 0);
viewColle.AddSubview(simpleCollectionViewController.View);
}
else if (count == 2)
{
simpleCollectionViewController = new MyCollectionViewController (flowLayout,count);
simpleCollectionViewController.CollectionView.ContentInset = new UIEdgeInsets (0, 0, 0, 0);
viewColle.AddSubview(simpleCollectionViewController.View);
}
else if (count == 3)
{
simpleCollectionViewController = new DetailViewController (flowLayout,1);
simpleCollectionViewController.CollectionView.ContentInset = new UIEdgeInsets (0, 0, 0, 0);
viewColle.AddSubview(simpleCollectionViewController.View);
}
nfloat height = 0;
CGRect contentRect2 = new CGRect();
foreach (UIView view in viewColle.Subviews) {
height += view.Bounds.Height;
}
contentRect2.Size = new CGSize(View.Bounds.Width, height );
viewColle.ContentSize = contentRect2.Size;
//viewColle.Frame = new CGRect(0, 100, UIScreen.MainScreen.Bounds.Width, 500);
//viewColle.ContentSize = new CGSize(simpleCollectionViewController.View.Bounds.Width, 2000);
View.AddSubview(btnClick);
View.AddSubview(viewColle);
};
}
public override void DidReceiveMemoryWarning()
{
base.DidReceiveMemoryWarning();
// Release any cached data, images, etc that aren't in use.
}
}
ListViewController Code:
public partial class ListViewController : UICollectionViewController
{
static NSString animalCellId = new NSString ("AnimalCell");
static NSString headerId = new NSString ("Header");
List<IProduct> products;
int devideValue = 0;
public ListViewController (UICollectionViewLayout layout,int divValue, int count) : base (layout)
{
devideValue = divValue;
products = new List<IProduct> ();
for (int i = 0; i < count; i++) {
Product pr = new Product();
pr.id = i;
pr.Price = i;
products.Add (pr);
}
}
[Export ("collectionView:layout:sizeForItemAtIndexPath:")]
public virtual CGSize GetSizeForItem (UICollectionView collectionView, UICollectionViewLayout layout, NSIndexPath indexPath)
{
//For 2 items devide by 2
var width = (float)(UIScreen.MainScreen.Bounds.Width/devideValue);
return new CGSize (width - 10, 125);
}
public override void ViewDidLoad ()
{
base.ViewDidLoad ();
CollectionView.RegisterClassForCell (typeof(ProductCell1), animalCellId);
CollectionView.RegisterClassForSupplementaryView (typeof(Header), UICollectionElementKindSection.Header, headerId);
UIMenuController.SharedMenuController.MenuItems = new UIMenuItem[] {
new UIMenuItem ("Add to Cart?", new Selector ("addCart"))
};
}
public override nint NumberOfSections (UICollectionView collectionView)
{
return 1;
}
public override nint GetItemsCount (UICollectionView collectionView, nint section)
{
return products.Count;
}
public override UICollectionViewCell GetCell (UICollectionView collectionView, NSIndexPath indexPath)
{
var productCell = (ProductCell1)collectionView.DequeueReusableCell (animalCellId, indexPath);
var product = products [indexPath.Row];
productCell.Image = product.Image;
productCell.Price = product.Price;
productCell.Product = product.ProductName;
return productCell;
}
public override UICollectionReusableView GetViewForSupplementaryElement (UICollectionView collectionView, NSString elementKind, NSIndexPath indexPath)
{
var headerView = (Header)collectionView.DequeueReusableSupplementaryView (elementKind, headerId, indexPath);
//headerView.Text = "Product View";
//headerView.btnText = "Click";
return headerView;
}
public override void ItemHighlighted (UICollectionView collectionView, NSIndexPath indexPath)
{
var cell = collectionView.CellForItem (indexPath);
cell.ContentView.BackgroundColor = UIColor.Red;
}
public override void ItemUnhighlighted (UICollectionView collectionView, NSIndexPath indexPath)
{
var cell = collectionView.CellForItem (indexPath);
cell.ContentView.BackgroundColor = UIColor.Green;
ProductCell1 productCell = (ProductCell1)collectionView.DequeueReusableCell (animalCellId, indexPath);
int itemIndex = (int)indexPath.Item;
Product prodt = new Product();
for (int i = 0; i < products.Count; i++)
{
if (indexPath.Item == i)
{
prodt = (Product)products[i];
break;
}
}
UIAlertView alert = new UIAlertView("Selected Item", prodt.id.ToString(), null, "Cancel", null);
alert.Show();
}
//public override void ItemSelected(UICollectionView collectionView, NSIndexPath indexPath)
//{
// //var cell = collectionView.CellForItem (indexPath);
// base.ItemSelected(collectionView, indexPath);
//}
public override bool ShouldHighlightItem (UICollectionView collectionView, NSIndexPath indexPath)
{
return true;
}
// for edit menu
public override bool ShouldShowMenu (UICollectionView collectionView, NSIndexPath indexPath)
{
return true;
}
public override bool CanPerformAction (UICollectionView collectionView, Selector action, NSIndexPath indexPath, NSObject sender)
{
// Selector should be the same as what's in the AddCart UIMenuItem
if (action == new Selector ("addCart"))
return true;
else
return false;
}
public override void PerformAction (UICollectionView collectionView, Selector action, NSIndexPath indexPath, NSObject sender)
{
System.Diagnostics.Debug.WriteLine ("code to perform action");
}
// CanBecomeFirstResponder and CanPerform are needed for a AddCart menu item to appear
public override bool CanBecomeFirstResponder {
get {
return true;
}
}
}
public class ProductCell1 : UICollectionViewCell
{
UIImageView imageView;
UILabel productName;
UILabel manufacturer;
UIView cellViewContainer;
UILabel price;
[Export ("initWithFrame:")]
public ProductCell1 (CGRect frame) : base (frame)
{
BackgroundView = new UIView{ BackgroundColor = UIColor.DarkGray };
SelectedBackgroundView = new UIView{ BackgroundColor = UIColor.Green };
ContentView.Layer.BorderColor = UIColor.LightGray.CGColor;
ContentView.Layer.BorderWidth = 2.0f;
ContentView.BackgroundColor = UIColor.Gray;
cellViewContainer = new UIView ();
cellViewContainer.AutoresizingMask = UIViewAutoresizing.FlexibleWidth | UIViewAutoresizing.FlexibleHeight;
imageView = new UIImageView (UIImage.FromBundle ("placeholder.png"));
productName = new UILabel {
Text = "Name",
TextColor = UIColor.Black,
BackgroundColor = UIColor.White,
TextAlignment = UITextAlignment.Left
};
manufacturer = new UILabel {
Text = "Price",
TextColor = UIColor.Black,
BackgroundColor = UIColor.Red,
TextAlignment = UITextAlignment.Left
};
price = new UILabel {
Text = "Price",
TextColor = UIColor.Black,
BackgroundColor = UIColor.Red,
TextAlignment = UITextAlignment.Left
};
//productName.Frame = new CGRect (5, 5, labelWidth, labelHeight);
//price.Frame = new CGRect (5, labelHeight, labelWidth, labelHeight);
//imageView.Frame = new CGRect (labelWidth, 0, labelWidth, ContentView.Bounds.Height - 2);
imageView.Frame = new CGRect (3,3, ContentView.Bounds.Width/2, ContentView.Bounds.Height-3);
productName.Frame = new CGRect (ContentView.Bounds.Width/2 + 5, 3, ContentView.Bounds.Width/2 - 5, 20);
manufacturer.Frame = new CGRect (ContentView.Bounds.Width/2 + 5, 23, ContentView.Bounds.Width/2 - 5, 20);
price.Frame = new CGRect (ContentView.Bounds.Width/2 + 5, 43, ContentView.Bounds.Width/2 - 5, 20);
ContentView.AddSubviews (new UIView[] { imageView, productName, manufacturer, price });
}
public void UpdateCell ()
{
productName.Frame = new CGRect (10, 10, ContentView.Bounds.Width / 2, ContentView.Bounds.Height / 3);
price.Frame = new CGRect (20, 20, ContentView.Bounds.Width / 2, ContentView.Bounds.Height / 3);
}
public UIImage Image {
set {
imageView.Image = value;
}
}
public string Product {
set {
productName.Text = value;
}
}
public double Price {
set {
price.Text = value.ToString ("$0.00");
}
}
[Export ("addCart")]
void AddCart ()
{
// Put all your addCart menu behavior code here
Console.WriteLine ("addCart in the cell");
}
public override bool CanPerform (Selector action, NSObject withSender)
{
if (action == new Selector ("addCart"))
return true;
else
return false;
}
}
after adding the items to view the scroll bar moves to top. Please can any one suggest me to solve this.