gistfile1.txt

using System;
using System.Collections.Generic;

using CoreGraphics;
using Foundation;
using UIKit;

namespace CustomDragExample
{
	public class CustomView : UIView
	{
		protected CustomView (IntPtr handle) : base (handle)
		{
		}

		public CustomView () : base ()
		{
		}

		public override void MovedToWindow ()
		{
			Layer.BackgroundColor = new CGColor (1, 0, 0);
		}
	}

	public class TableHandler : NSObject, IUITableViewDelegate, IUITableViewDataSource, IUITableViewDropDelegate
	{
		List<string> Data = new List<string> () { "One", "Two", "Three", "Four", "Five", "Six", "Seven", "Eight" };
		public const string MyCellIdentifier = "ViewController.CellIdentifier";

		[Export ("tableView:cellForRowAtIndexPath:")]
		public UITableViewCell GetCell (UITableView tableView, NSIndexPath indexPath)
		{
			UITableViewCell cell = tableView.DequeueReusableCell (MyCellIdentifier, indexPath);
			cell.TextLabel.Text = Data[(int)indexPath.Item];
			return cell;
		}

		[Export ("tableView:numberOfRowsInSection:")]
		public nint RowsInSection (UITableView tableView, nint section) => Data.Count;

		[Export ("tableView:canEditRowAtIndexPath:")]
		public bool CanEditRow (UITableView tableView, NSIndexPath indexPath) => true;

		[Export ("tableView:performDropWithCoordinator:")]
		public void PerformDrop (UITableView tableView, IUITableViewDropCoordinator coordinator)
		{
			// BUG
			Console.WriteLine ("PerformDrop");
			var destPath = coordinator.DestinationIndexPath;

			if (coordinator.Session.CanLoadObjects (typeof (NSString))) {
				coordinator.Session.LoadObjects (typeof (NSString), (items => {
					Console.WriteLine ("LoadObjects");

					// I would expect this to work
					var strings = items as NSString[];
					Console.WriteLine (strings == null);

					// But the underlying item is a string
					var v = ObjCRuntime.Runtime.GetNSObject<NSString> (items[0].Handle);
					Console.WriteLine (v);
				}));
			}
		}
	}

	public class DragHandler : NSObject, IUIDragInteractionDelegate, IUIDropInteractionDelegate
	{
		[Export ("dragInteraction:itemsForBeginningSession:")]
		public UIDragItem[] GetItemsForBeginningSession (UIDragInteraction interaction, IUIDragSession session)
		{
			NSString s = (NSString)"asdf";
			NSItemProvider p = new NSItemProvider (s);
			return new UIDragItem[] { new UIDragItem (p) };
		}

		[Export ("tableView:canHandleDropSession:")]
		public bool CanHandleDropSession (UITableView tableView, IUIDropSession session) => true;

		[Export ("tableView:dropSessionDidUpdate:withDestinationIndexPath:")]
		public UITableViewDropProposal DropSessionDidUpdate (UITableView tableView, IUIDropSession session, NSIndexPath destinationIndexPath)
		{
			if (tableView.HasActiveDrag) {
				if (session.Items.Length > 1)
					return new UITableViewDropProposal (UIDropOperation.Cancel);
				return new UITableViewDropProposal (UIDropOperation.Move, UITableViewDropIntent.InsertAtDestinationIndexPath);
			}
			return new UITableViewDropProposal (UIDropOperation.Copy, UITableViewDropIntent.InsertAtDestinationIndexPath);
		}
	}

	public partial class ViewController : UIViewController 
	{
		TableHandler TableBehavior = new TableHandler ();
		DragHandler DragBehavior = new DragHandler ();

		protected ViewController (IntPtr handle) : base (handle)
		{
		}

		public override void ViewDidLoad ()
		{
			base.ViewDidLoad ();

			UIStackView stack = new UIStackView (View.Bounds) {
				Axis = UILayoutConstraintAxis.Horizontal,
				Spacing = 10
			};

			View.AddSubview (stack);

			CustomView leftView = new CustomView {
				UserInteractionEnabled = true
			};
			var drag = new UIDragInteraction (DragBehavior) {
				Enabled = true
			};
			leftView.AddInteraction (drag);

			UITableView rightView = new UITableView () {
				Delegate = TableBehavior,
				DataSource = TableBehavior,
				DropDelegate = TableBehavior
			};

			rightView.RegisterClassForCellReuse (typeof (UITableViewCell), TableHandler.MyCellIdentifier);

			stack.AddArrangedSubview (leftView);
			stack.AddArrangedSubview (rightView);

			SetupConstraints (stack, leftView, rightView);
		}

		void SetupConstraints (UIStackView stack, UIView leftView, UIView rightView)
		{
			var margins = View.LayoutMarginsGuide;

			stack.TranslatesAutoresizingMaskIntoConstraints = false;
			stack.LeadingAnchor.ConstraintEqualTo (margins.LeadingAnchor).Active = true;
			stack.TrailingAnchor.ConstraintEqualTo (margins.TrailingAnchor).Active = true;

			stack.TopAnchor.ConstraintEqualTo (margins.TopAnchor, 15).Active = true;
			stack.BottomAnchor.ConstraintEqualTo (margins.BottomAnchor, -15).Active = true;

			leftView.WidthAnchor.ConstraintEqualTo (margins.WidthAnchor, (nfloat).33).Active = true;

			rightView.WidthAnchor.ConstraintEqualTo (margins.WidthAnchor, (nfloat).66).Active = true;
		}
	}
}