Dynamic UIViewPageController for Xamarin iOS

DPageViewController.cs

using System;
using UIKit;
using System.Collections.Generic;
using CoreGraphics;

// ported from https://github.com/nsobadzhiev/DynamicPageViewController/blob/master/DynamicPageViewController/DMDynamicViewController.swift

namespace YourNamespace
{
	/*protocol DMDynamicPageViewControllerDelegate {
		func pageViewController(pageController: DMDynamicViewController, didSwitchToViewController viewController: UIViewController)
		func pageViewController(pageController: DMDynamicViewController, didChangeViewControllers viewControllers: Array<UIViewController>)
	}*/

	public class DPageViewController: UIViewController, IUIScrollViewDelegate {

		/*var delegate: DMDynamicPageViewControllerDelegate? = nil
		 
		func notifyDelegateDidSwitchPage() {
			self.delegate?.pageViewController(self, didSwitchToViewController: self.viewControllers![self.currentPage])
		}

		func notifyDelegateDidChangeControllers() {
			self.delegate?.pageViewController(self, didChangeViewControllers: self.viewControllers!)
		}*/

		UIScrollView containerScrollView;
		nfloat pageWidth = 1f;						
		public List<UIViewController> ViewControllers;

		int _currentPage;
		public int CurrentPage {
			get { return _currentPage; }
			set {
				_currentPage = value;
				if (_currentPage >= ViewControllers.Count)
				{
					_currentPage = ViewControllers.Count - 1;
				}
				containerScrollView.Delegate = null;
				containerScrollView.ContentOffset = new CGPoint ((nfloat)_currentPage * View.Bounds.Size.Width, 0.0);
				containerScrollView.Delegate = this;
				// Set the fully switched page in order to notify the delegates about it if needed.
				FullySwitchedPage = CurrentPage;
			}
		}
			
		int _fullySwitchedPage;
		public int FullySwitchedPage {
			get { return _fullySwitchedPage; }
			set {				
				if (value != _fullySwitchedPage) {
					// The page is fully switched.
					if (_fullySwitchedPage < ViewControllers.Count) {
					    var previousViewController = ViewControllers[_fullySwitchedPage];
					    // Perform the "disappear" sequence of methods manually when the view of
					    // the controller is not visible at all.
						previousViewController.WillMoveToParentViewController(this);
						previousViewController.ViewWillDisappear (false);
						previousViewController.ViewDidDisappear (false);
						previousViewController.DidMoveToParentViewController (this);
						previousViewController.WillMoveToParentViewController (this);
						previousViewController.ViewWillAppear (false);
						previousViewController.ViewDidAppear (false);
						previousViewController.DidMoveToParentViewController (this);
				    }
				}
				_fullySwitchedPage = value;
			}
		}

		public DPageViewController(List<UIViewController> viewControllers) {
			//super.init(nibName: nil, bundle: nil)
			ViewControllers = viewControllers;
			//self.notifyDelegateDidChangeControllers()
		}

		/*init(viewControllers: Array<UIViewController>) {
			super.init(nibName: nil, bundle: nil)
			self.viewControllers = viewControllers
			self.notifyDelegateDidChangeControllers()
		}

		required override init(nibName nibN		ameOrNil: String!, bundle nibBundleOrNil: NSBundle!) {
			super.init(nibName: nibNameOrNil, bundle: nibBundleOrNil)
		}

		required init(coder: NSCoder) {
			super.init(coder: coder)
		}*/

		public override void ViewDidLoad() {
			base.ViewDidLoad ();
			containerScrollView = new UIScrollView (new CGRect(0, 44, View.Frame.Size.Width, View.Frame.Size.Height - 90)); //frame: self.view.bounds
			containerScrollView.PagingEnabled = true;
			containerScrollView.AlwaysBounceVertical = false;
			containerScrollView.AlwaysBounceHorizontal = true; // drag with only one view controller
			containerScrollView.ShowsHorizontalScrollIndicator = false;
			containerScrollView.Delegate = this;
			pageWidth = View.Frame.Size.Width;
			View.AddSubview(containerScrollView);
			LayoutPages();
		}

		public override void ViewDidLayoutSubviews() {
			for (var i = 0; i < ViewControllers.Count; i += 1) {
				var pageX = (nfloat)i * View.Bounds.Size.Width;
				ViewControllers [i].View.Frame = new CGRect (pageX, 0.0, View.Bounds.Size.Width, View.Bounds.Size.Height);
			}
			// It is important to set the pageWidth property before the contentSize and contentOffset,
			// in order to use the new width into scrollView delegate methods.
			pageWidth = View.Bounds.Size.Width;
			containerScrollView.ContentSize = new CGSize ((nfloat)ViewControllers.Count * View.Bounds.Size.Width, 1.0);
			containerScrollView.ContentOffset = new CGPoint ((nfloat)CurrentPage * View.Bounds.Size.Width, 0.0);
		}

		public override void DidReceiveMemoryWarning() {
			base.DidReceiveMemoryWarning ();
			// Dispose of any resources that can be recreated.
		}

		void LayoutPages() {

			foreach(var pageView in containerScrollView.Subviews) {
				pageView.RemoveFromSuperview();
			}

			for (var i = 0; i < ViewControllers.Count; i++) {
				var page = ViewControllers [i];
				AddChildViewController(page);
				var nextFrame = new CGRect ((nfloat)i * View.Bounds.Size.Width, View.Frame.Y, View.Frame.Size.Width, View.Frame.Size.Height); // Origin.Y
				page.View.Frame = nextFrame;
				containerScrollView.AddSubview (page.View);
				page.DidMoveToParentViewController (this);
			}
			containerScrollView.ContentSize = new CGSize(View.Bounds.Size.Width * (nfloat)ViewControllers.Count, 1.0);
		}

		void WillMoveToParentViewController() {
			var page = (int)((containerScrollView.ContentOffset.X - pageWidth / 2.0) / pageWidth) + 1;
			if (CurrentPage != page)
			{
				CurrentPage = page;
				//FullySwitchedPage = page;
			}
		}

		public void InsertPage(UIViewController viewController, int index) {
			ViewControllers.Insert(index, viewController);
			LayoutPages();
			CurrentPage = index;
			//self.notifyDelegateDidChangeControllers()
		}

		public void RemovePage(UIViewController viewController) {
			for (var i = 0; i < ViewControllers.Count; i += 1) {
				if (ViewControllers[i] == viewController) {
					ViewControllers.RemoveAt (i);
					LayoutPages();
					//self.notifyDelegateDidChangeControllers()
				}
			}
		}

		// MARK: UIScrollViewDelegate

		[Foundation.Export ("scrollViewDidScroll:")]
		public void Scrolled (UIScrollView scrollView)
		{
			// Update the page when more than 50% of the previous/next page is visible
			var page = Math.Floor((containerScrollView.ContentOffset.X - pageWidth / 2) / pageWidth) + 1;

			/*if (CurrentPage != (int)page) {
				// Check the page to avoid "index out of bounds" exception.
				if (page >= 0 && (int)page < ViewControllers.Count)
				{
					//self.notifyDelegateDidSwitchPage()
				}
			}*/

			// Check whether the current view controller is fully presented.
			if ((int)containerScrollView.ContentOffset.X % (int)pageWidth == 0)
			{
				CurrentPage = (int)page;
				//FullySwitchedPage = CurrentPage;
			}
		}
	}
}