private void EnableDragAndDrop(bool isEnabled, DragAndDropTrigger dragAndDropTrigger)
{
if (_dragAndDropGesture != null)
{
Control.RemoveGestureRecognizer(_dragAndDropGesture);
_dragAndDropGesture = null;
return;
}
if (!isEnabled)
{
return;
}
int from = -1;
NSIndexPath pathTo = null;
iOSViewCell draggedViewCell = null;
// Create a custom gesture recognizer
_dragAndDropGesture = dragAndDropTrigger == DragAndDropTrigger.Pan
? new UIPanGestureRecognizer(
gesture =>
{
// Take action based on state
HandleDragByGestureState(gesture.State, gesture, ref from, ref pathTo, ref draggedViewCell);
})
: new UILongPressGestureRecognizer(
gesture =>
{
// Take action based on state
HandleDragByGestureState(gesture.State, gesture, ref from, ref pathTo, ref draggedViewCell);
});
// Add the custom recognizer to the collection view
Control.AddGestureRecognizer(_dragAndDropGesture);
}
private void HandleDragByGestureState(
UIGestureRecognizerState state,
UIGestureRecognizer gesture,
ref int from,
ref NSIndexPath pathTo,
ref iOSViewCell draggedViewCell)
{
switch (state)
{
case UIGestureRecognizerState.Began:
var selectedIndexPath = Control.IndexPathForItemAtPoint(gesture.LocationInView(Control));
if (selectedIndexPath != null)
{
draggedViewCell = (iOSViewCell)Control.CellForItem(selectedIndexPath);
if (draggedViewCell.FormsCell is DraggableViewCell draggableViewCell)
{
if (!draggableViewCell.IsDraggable)
{
Control.CancelInteractiveMovement();
return;
}
draggableViewCell.IsDragAndDropping = true;
}
from = (int)selectedIndexPath.Item;
Control.BeginInteractiveMovementForItem(selectedIndexPath);
Element.IsDragAndDropping = true;
Element.DragAndDropStartedCommand?.Execute(
new DragAndDropInfo(from, -1, Element.BindingContext));
}
break;
case UIGestureRecognizerState.Changed:
if (draggedViewCell == null)
{
return;
}
var gestureLocation = gesture.LocationInView(gesture.View);
var changedPath = Control.IndexPathForItemAtPoint(gestureLocation);
if (changedPath != null)
{
draggedViewCell = (iOSViewCell)Control.CellForItem(changedPath);
if (draggedViewCell == null ||
(draggedViewCell.FormsCell is DraggableViewCell draggableViewCell &&
!draggableViewCell.IsDraggable))
{
pathTo = null;
// System.Diagnostics.Debug.WriteLine("Cancel change state");
return;
}
pathTo = changedPath;
// System.Diagnostics.Debug.WriteLine($"State changed to {pathTo.Item}");
}
switch (Element.DragAndDropDirection)
{
case DragAndDropDirection.HorizontalOnly:
Control.UpdateInteractiveMovement(new CGPoint(gestureLocation.X, draggedViewCell.Center.Y));
break;
case DragAndDropDirection.VerticalOnly:
Control.UpdateInteractiveMovement(new CGPoint(draggedViewCell.Center.X, gestureLocation.Y));
break;
default:
Control.UpdateInteractiveMovement(gestureLocation);
break;
}
break;
case UIGestureRecognizerState.Ended:
if (from < 0 || pathTo == null)
{
// System.Diagnostics.Debug.WriteLine($"Ended but cancelled cause incorrect parameters");
Control.CancelInteractiveMovement();
return;
}
var targetViewCell = (iOSViewCell)Control.CellForItem(pathTo);
if (targetViewCell?.FormsCell is DraggableViewCell targetDraggableViewCell &&
!targetDraggableViewCell.IsDraggable)
{
// System.Diagnostics.Debug.WriteLine($"Ended but cancelled cause target is not draggable");
Control.CancelInteractiveMovement();
return;
}
// System.Diagnostics.Debug.WriteLine($"Ended from: {from} to: {pathTo.Item}");
Control.EndInteractiveMovement();
if (_itemsSource is IList itemsSourceList)
{
try
{
_isMovedBackfire = true;
var item = itemsSourceList[from];
itemsSourceList.RemoveAt(from);
itemsSourceList.Insert((int)pathTo.Item, item);
var to = itemsSourceList.IndexOf(item);
Element.IsDragAndDropping = false;
if (draggedViewCell?.FormsCell is DraggableViewCell draggableViewCell)
{
draggableViewCell.IsDragAndDropping = false;
Element.DragAndDropEndedCommand?.Execute(
new DragAndDropInfo(from, to, draggableViewCell.BindingContext));
}
draggedViewCell = null;
}
finally
{
_isMovedBackfire = false;
}
}
break;
default:
Control.CancelInteractiveMovement();
break;
}
}
