private void DropTarget_PreviewDrop(object sender, DragEventArgs e)
{
var draggedItems = e.Data.GetData(this.format.Name) as List <object>;
var indiciesRemoved = new List <int>();
if (draggedItems != null)
{
if ((e.Effects & DragDropEffects.Move) != 0)
{
indiciesRemoved = DragDropUtilities.RemoveItemsFromItemsControl(this.sourceItemsControl, draggedItems);
}
// If we're dragging to the same list, adjust the insertion point to account for removed items.
if (this.sourceItemsControl == this.targetItemsControl)
{
int itemCountBeforeInsertionPoint = indiciesRemoved.Where(t => t < this.insertionIndex).Count();
this.insertionIndex -= itemCountBeforeInsertionPoint;
}
DragDropUtilities.InsertItemsInItemsControl(this.targetItemsControl, draggedItems, this.insertionIndex);
this.RemoveDraggedAdorner();
this.RemoveInsertionAdorner();
}
e.Handled = true;
}
// Drag = mouse down + move by a certain amount
private void DragSource_PreviewMouseMove(object sender, MouseEventArgs e)
{
if (this.draggedData != null)
{
// Only drag when user moved the mouse by a reasonable amount.
if (DragDropUtilities.IsMovementBigEnough(this.initialMousePosition, e.GetPosition(this.topWindow)))
{
var draggedItems = this.draggedData as List <object>;
var listView = this.sourceItemsControl as ListView;
if (listView != null)
{
// Once the drag has started, we must re-select the originally dragged items. The initial click may have de-selected them.
listView.SelectedItems.Clear();
foreach (object item in draggedItems)
{
listView.SelectedItems.Add(item);
}
}
DataObject data;
try
{
data = new DataObject(this.format.Name, this.draggedData);
}
catch (COMException exception)
{
// Not sure what's going on here, can't reproduce. Hopefully this will allow the next drag operation to succeed.
Ioc.Get <IAppLogger>().LogError("Error during drag operation:" + Environment.NewLine + Environment.NewLine + exception);
this.draggedData = null;
return;
}
// Adding events to the window to make sure dragged adorner comes up when mouse is not over a drop target.
bool previousAllowDrop = this.topWindow.AllowDrop;
this.topWindow.AllowDrop = true;
this.topWindow.DragEnter += this.TopWindow_DragEnter;
this.topWindow.DragOver += this.TopWindow_DragOver;
this.topWindow.DragLeave += this.TopWindow_DragLeave;
DragDropEffects effects = DragDrop.DoDragDrop((DependencyObject)sender, data, DragDropEffects.Move);
// Without this call, there would be a bug in the following scenario: Click on a data item, and drag
// the mouse very fast outside of the window. When doing this really fast, for some reason I don't get
// the Window leave event, and the dragged adorner is left behind.
// With this call, the dragged adorner will disappear when we release the mouse outside of the window,
// which is when the DoDragDrop synchronous method returns.
this.RemoveDraggedAdorner();
this.topWindow.AllowDrop = previousAllowDrop;
this.topWindow.DragEnter -= this.TopWindow_DragEnter;
this.topWindow.DragOver -= this.TopWindow_DragOver;
this.topWindow.DragLeave -= this.TopWindow_DragLeave;
this.draggedData = null;
}
}
}
// DragSource
private void DragSource_PreviewMouseLeftButtonDown(object sender, MouseButtonEventArgs e)
{
this.sourceItemsControl = (ItemsControl)sender;
var visual = e.OriginalSource as Visual;
this.topWindow = (Window)DragDropUtilities.FindAncestor(typeof(Window), this.sourceItemsControl);
this.initialMousePosition = e.GetPosition(this.topWindow);
this.sourceItemContainer = DragDropUtilities.GetItemContainer(this.sourceItemsControl, visual);
if (this.sourceItemContainer != null)
{
object clickedItem = this.sourceItemContainer.DataContext;
var itemsToDrag = new List <object>();
var listView = this.sourceItemsControl as ListView;
if (listView != null && listView.SelectedItems.Contains(clickedItem))
{
// If we clicked on a selected item, do a multi-drag
// The selected items aren't always in order so we need to sort by index first.
var itemIndices = (from object selectedItem in listView.SelectedItems select this.sourceItemsControl.Items.IndexOf(selectedItem)).ToList();
itemIndices.Sort();
itemsToDrag.AddRange(itemIndices.Select(index => this.sourceItemsControl.Items[index]));
}
else
{
// If we clicked on an unselected item, do a single drag
itemsToDrag.Add(clickedItem);
}
// Cull items that can't be dragged
for (int i = itemsToDrag.Count - 1; i >= 0; i--)
{
var dragData = itemsToDrag[i] as IDragItem;
if (dragData != null && !dragData.CanDrag)
{
itemsToDrag.RemoveAt(i);
}
}
if (itemsToDrag.Count > 0)
{
this.draggedData = itemsToDrag;
}
}
}
// If the types of the dragged data and ItemsControl's source are compatible,
// there are 3 situations to have into account when deciding the drop target:
// 1. mouse is over an items container
// 2. mouse is over the empty part of an ItemsControl, but ItemsControl is not empty
// 3. mouse is over an empty ItemsControl.
// The goal of this method is to decide on the values of the following properties:
// targetItemContainer, insertionIndex and isInFirstHalf.
private void DecideDropTarget(DragEventArgs e)
{
int targetItemsControlCount = this.targetItemsControl.Items.Count;
var draggedItems = e.Data.GetData(this.format.Name) as List <object>;
this.targetItemContainer = null;
if (draggedItems != null && this.IsDropDataTypeAllowed(draggedItems[0]))
{
if (targetItemsControlCount > 0)
{
this.hasVerticalOrientation = DragDropUtilities.HasVerticalOrientation(this.targetItemsControl.ItemContainerGenerator.ContainerFromIndex(0) as FrameworkElement);
// Hack, only works with vertical orientation lists. Original code assumed dragging to end of list if no
// item is hovered over; this is incorrect.
for (int i = 0; i < targetItemsControlCount; i++)
{
FrameworkElement currentItemContainer = this.targetItemsControl.ItemContainerGenerator.ContainerFromIndex(i) as FrameworkElement;
if (currentItemContainer != null)
{
Point relativeDistanceFromItem = e.GetPosition(currentItemContainer);
if (relativeDistanceFromItem.Y < 0)
{
this.targetItemContainer = currentItemContainer;
break;
}
if (relativeDistanceFromItem.Y < currentItemContainer.ActualHeight)
{
this.targetItemContainer = currentItemContainer;
break;
}
}
}
if (this.targetItemContainer != null)
{
Point positionRelativeToItemContainer = e.GetPosition(this.targetItemContainer);
this.isInFirstHalf = DragDropUtilities.IsInFirstHalf(this.targetItemContainer, positionRelativeToItemContainer, this.hasVerticalOrientation);
this.insertionIndex = this.targetItemsControl.ItemContainerGenerator.IndexFromContainer(this.targetItemContainer);
if (!this.isInFirstHalf)
{
this.insertionIndex++;
}
}
else
{
this.targetItemContainer = this.targetItemsControl.ItemContainerGenerator.ContainerFromIndex(targetItemsControlCount - 1) as FrameworkElement;
this.isInFirstHalf = false;
this.insertionIndex = targetItemsControlCount;
}
if (this.insertionIndex == 0 && !GetAllowDropAtTop(this.sourceItemsControl))
{
this.targetItemContainer = null;
this.insertionIndex = -1;
e.Effects = DragDropEffects.None;
}
}
else
{
this.insertionIndex = 0;
}
}
else
{
this.insertionIndex = -1;
e.Effects = DragDropEffects.None;
}
}
