private void DoDragAndDropEnd(FrameworkElement dropTarget)
{
// Get the event handler.
DragAndDropDelegate dragAndDropEnd = DragAndDropEnd;
// If we have the event handler, fire it.
if (dragAndDropEnd != null)
{
DragAndDropEventArgs args = new DragAndDropEventArgs()
{
Allow = true,
DragSource = dragSource,
DragElement = dragElement,
DragData = dragData,
DropTarget = dropTarget
};
dragAndDropEnd(this, args);
}
// We're done.
dragging = false;
dragData = null;
dragElement = null;
dragSource = null;
dropTarget = null;
dragAdorner = null;
}
/// <summary>
/// Continues drag and drop, calling the appropriate event if it is registered.
/// </summary>
/// <param name="potentialDropTarget">The potential drop target.</param>
private void DoContinueDragAndDrop(FrameworkElement potentialDropTarget)
{
// If we have a start handler, call it.
DragAndDropDelegate dragAndDropContinue = DragAndDropContinue;
if (dragAndDropContinue != null)
{
// Create the drag and drop event args.
DragAndDropEventArgs args = new DragAndDropEventArgs()
{
DragSource = dragSource,
DragElement = dragElement,
DragData = dragData,
DropTarget = potentialDropTarget,
Allow = true
};
// Call the event.
dragAndDropContinue(this, args);
// If the operation has been disallowed, return.
if (args.Allow == false)
{
return;
}
}
// Store the potential drop target.
dropTarget = potentialDropTarget;
}
/// <summary>
/// Starts drag and drop, calling the appropriate event if it is registered.
/// </summary>
/// <param name="dragSource">The drag source.</param>
/// <param name="dragElement">The drag element.</param>
/// <param name="dragData">The drag data.</param>
private void DoDragAndDropStart(FrameworkElement dragSource, FrameworkElement dragElement,
object dragData)
{
// If we have a start handler, call it.
DragAndDropDelegate dragAndDropStart = DragAndDropStart;
if (dragAndDropStart != null)
{
// Create the drag args.
DragAndDropEventArgs args = new DragAndDropEventArgs()
{
DragSource = dragSource,
DragElement = dragElement,
DragData = dragData,
Allow = true
};
// Call the event handler.
dragAndDropStart(this, args);
// Has the operation been disallowed?
if (args.Allow == false)
{
// todo extrapolate to function
dragging = false;
dragData = null;
dragElement = null;
dragSource = null;
dropTarget = null;
dragAdorner = null;
return;
}
// Do we have an adorner?
if (args.DragAdorner != null)
{
// Add the adorner.
dragAdorner = args.DragAdorner;
adornerLayer.AddAdorner(dragAdorner);
}
}
// Allow the drag.
dragging = true;
}
private void DoContinueDragAndDrop(FrameworkElement potentialDropTarget)
{
// If we have a start handler, call it.
DragAndDropDelegate dragAndDropContinue = DragAndDropContinue;
if (dragAndDropContinue != null)
{
DragAndDropEventArgs args = new DragAndDropEventArgs()
{
DragSource = dragSource,
DragElement = dragElement,
DragData = dragData,
DropTarget = potentialDropTarget,
Allow = true
};
dragAndDropContinue(this, args);
if (args.Allow == false)
{
return;
}
}
dropTarget = potentialDropTarget;
}
void LoadRecognizers()
{
if (ElementGestureRecognizers == null)
{
return;
}
#if __MOBILE__
if (_shouldReceiveTouch == null)
{
// Cache this so we don't create a new UITouchEventArgs instance for every recognizer
_shouldReceiveTouch = ShouldReceiveTouch;
}
#endif
#if __MOBILE__
UIDragInteraction uIDragInteraction = null;
UIDropInteraction uIDropInteraction = null;
if (_dragAndDropDelegate != null)
{
foreach (var interaction in _renderer.NativeView.Interactions)
{
if (interaction is UIDragInteraction uIDrag && uIDrag.Delegate == _dragAndDropDelegate)
{
uIDragInteraction = uIDrag;
}
if (interaction is UIDropInteraction uiDrop && uiDrop.Delegate == _dragAndDropDelegate)
{
uIDropInteraction = uiDrop;
}
}
}
bool dragFound = false;
bool dropFound = false;
#endif
for (int i = 0; i < ElementGestureRecognizers.Count; i++)
{
IGestureRecognizer recognizer = ElementGestureRecognizers[i];
if (_gestureRecognizers.ContainsKey(recognizer))
{
continue;
}
var nativeRecognizer = GetNativeRecognizer(recognizer);
if (nativeRecognizer != null && _handler != null)
{
#if __MOBILE__
nativeRecognizer.ShouldReceiveTouch = _shouldReceiveTouch;
#endif
_handler.AddGestureRecognizer(nativeRecognizer);
_gestureRecognizers[recognizer] = nativeRecognizer;
}
#if __MOBILE__
if (Forms.IsiOS11OrNewer && recognizer is DragGestureRecognizer)
{
dragFound = true;
_dragAndDropDelegate = _dragAndDropDelegate ?? new DragAndDropDelegate();
if (uIDragInteraction == null)
{
var interaction = new UIDragInteraction(_dragAndDropDelegate);
interaction.Enabled = true;
_renderer.NativeView.AddInteraction(interaction);
}
}
if (Forms.IsiOS11OrNewer && recognizer is DropGestureRecognizer)
{
dropFound = true;
_dragAndDropDelegate = _dragAndDropDelegate ?? new DragAndDropDelegate();
if (uIDropInteraction == null)
{
var interaction = new UIDropInteraction(_dragAndDropDelegate);
_renderer.NativeView.AddInteraction(interaction);
}
}
#endif
}
#if __MOBILE__
if (!dragFound && uIDragInteraction != null)
{
_renderer.NativeView.RemoveInteraction(uIDragInteraction);
}
if (!dropFound && uIDropInteraction != null)
{
_renderer.NativeView.RemoveInteraction(uIDropInteraction);
}
#endif
var toRemove = _gestureRecognizers.Keys.Where(key => !ElementGestureRecognizers.Contains(key)).ToArray();
for (int i = 0; i < toRemove.Length; i++)
{
IGestureRecognizer gestureRecognizer = toRemove[i];
var uiRecognizer = _gestureRecognizers[gestureRecognizer];
_gestureRecognizers.Remove(gestureRecognizer);
_handler.RemoveGestureRecognizer(uiRecognizer);
uiRecognizer.Dispose();
}
}
