Created
May 21, 2012 17:06
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A useful drag and drop extension method
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public static void SetupDragging(this ListView list) | |
{ | |
bool insertAfter = false; | |
ListViewItem dragged = null; | |
ListViewItem targetItem = null; | |
list.DrawItem += (o, e) => | |
{ | |
e.DrawDefault = true; | |
if (e.Item != targetItem) return; | |
e.DrawDefault = false; | |
e.DrawBackground(); | |
e.DrawFocusRectangle(); | |
e.DrawText(); | |
using (var pen = new Pen(Color.DarkGreen, 1.0f)) | |
{ | |
Point start = new Point(e.Bounds.Left + e.Bounds.Width / 4, insertAfter ? e.Bounds.Bottom - 1 : e.Bounds.Top); | |
Point end = new Point(e.Bounds.Width - e.Bounds.Width / 4, insertAfter ? e.Bounds.Bottom - 1 : e.Bounds.Top); | |
e.Graphics.DrawLine(pen, start, end); | |
} | |
}; | |
list.ItemDrag += (o, e) => | |
{ | |
list.OwnerDraw = true; | |
dragged = (ListViewItem)e.Item; | |
list.DoDragDrop(e.Item, DragDropEffects.Move); | |
}; | |
bool hovering = false; | |
list.DragOver += (o, e) => | |
{ | |
Point targetPoint = list.PointToClient(new Point(e.X, e.Y)); | |
targetItem = list.GetItemAt(targetPoint.X, targetPoint.Y); | |
Rectangle itemBounds = targetItem.Bounds; | |
bool atTopItem = list.TopItem == targetItem && list.Items[0] != targetItem; | |
bool atBottomItem = targetPoint.Y > list.Height - itemBounds.Height && targetItem.Index < list.Items.Count - 1; | |
if (!hovering && atTopItem) | |
{ | |
hovering = true; | |
Timer t = new Timer { Interval = 400 }; | |
ListViewItem currentTarget = targetItem; | |
t.Tick += (o1, e1) => | |
{ | |
t.Stop(); | |
if (currentTarget == targetItem) | |
{ | |
list.Items[currentTarget.Index - 1].EnsureVisible(); | |
} | |
hovering = false; | |
}; | |
t.Start(); | |
} | |
else if (!hovering && atBottomItem) | |
{ | |
hovering = true; | |
Timer t = new Timer { Interval = 400 }; | |
ListViewItem currentTarget = targetItem; | |
t.Tick += (o1, e1) => | |
{ | |
t.Stop(); | |
if (currentTarget == targetItem) | |
{ | |
list.Items[currentTarget.Index + 1].EnsureVisible(); | |
} | |
hovering = false; | |
}; | |
t.Start(); | |
} | |
else if (hovering && !atTopItem && !atBottomItem) | |
{ | |
hovering = false; | |
} | |
if (targetItem == dragged) targetItem = null; | |
if (targetItem == null) | |
{ | |
e.Effect = DragDropEffects.None; | |
list.Invalidate(); | |
} | |
else | |
{ | |
e.Effect = DragDropEffects.Move; | |
insertAfter = targetPoint.Y > itemBounds.Top + (itemBounds.Height / 2); | |
itemBounds.Inflate(10, 10); | |
itemBounds.Offset(-5, -5); | |
list.Invalidate(itemBounds); | |
} | |
}; | |
list.DragEnter += (o, e) => | |
{ | |
list.OwnerDraw = dragged != null; | |
list.Invalidate(); | |
}; | |
list.DragLeave += (o, e) => | |
{ | |
list.OwnerDraw = false; | |
targetItem = null; | |
list.Invalidate(); | |
}; | |
list.DragDrop += (o, e) => | |
{ | |
if (targetItem != null) | |
{ | |
int targetIndex = targetItem.Index; | |
if (insertAfter) ++targetIndex; | |
var tmp = new ListViewItem(); | |
list.Items.Insert(targetIndex, tmp); | |
list.Items.Remove(dragged); | |
list.Items.Insert(tmp.Index, dragged); | |
list.Items.Remove(tmp); | |
} | |
list.OwnerDraw = false; | |
list.Invalidate(); | |
}; | |
} |
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Very handy so you don't reuse the same code over and over. Allows you to re-order the items in a
DetailMode
non-virtual list view by simply callingSetupDragging
on the list view.