Listbox drag-reorder：已删除项目的索引 [英] Listbox drag-reorder : Index of the dropped item

问题描述

我正在使用 Listbox 包装在一个 ListBoxDragDropTarget （从Silverlight工具包）。
这个 ListBox 可以由用户手动重新排序。但是最后一个项目必须始终位于 ListBox 的底部，并且根本无法移动。我找到了一种取消最后一个项目移动的方法，但是如果我拖放下一个项目 最后一个项目，它将被移动。

I'm using a Listbox wrapped inside a ListBoxDragDropTarget (from the Silverlight toolkit). This ListBox ca be manually reordered by the user. However the last item must always be located at the bottom of the ListBox, and can't be moved at all. I found a way to cancel this last item moves, but if I drag and drop another item below this last item, it gets moved.

我可以在ListBox的 Drop 事件中使用此代码找到拖动项目的索引：

I can find the index of the dragged item using this code in the Drop event of the ListBox:

object data = e.Data.GetData(e.Data.GetFormats()[0]);

ItemDragEventArgs dragEventArgs = data as ItemDragEventArgs;
SelectionCollection selectionCollection = dragEventArgs.Data as SelectionCollection;
if (selectionCollection != null)
{
    MyClass cw = selectionCollection[0].Item as MyClass;
    int idx = selectionCollection[0].Index.Value;   
}

然而，这只给了我之前的拖动操作。

However this only gives me the index before the drag operation.

我的问题如下：有没有办法知道删除的项目的新的索引？这样，如果索引=列表的最后一个位置，我可以将其移动到最后的位置。

My question is the following: Is there a way to know the new index of the dropped item ? This way, if the index = last position of the list, I can move it to the forelast position.

提前感谢！

推荐答案

好的，我找到了一个办法。我绑定了 ListBoxDragDropTarget 的 ItemDragCompleted 事件，并执行了以下操作：

Ok I found a way to do this. I bound the ItemDragCompleted event of the ListBoxDragDropTarget, and did the following:

private void dropTarget1_ItemDragCompleted(object sender, ItemDragEventArgs e)
{
    var tmp = (e.DragSource as ListBox).ItemsSource.Cast<MyClass>().ToList();

    SelectionCollection selectionCollection = e.Data as SelectionCollection;
    if (selectionCollection != null)
    {
        MyClass cw = selectionCollection[0].Item as MyClass;

        int idx = tmp.IndexOf(cw);
        if (idx == tmp.Count - 1)
        {
            tmp.Remove(cw);
            tmp.Insert(tmp.Count - 1, cw);

            MyListBox.ItemsSource = new ObservableCollection<MyClass>(tmp);
        }
}

}

由于DragSource代表列表框，使用新的安排项目，因此我可以检查项目是否位于最后，并在这种情况下移动。

As the DragSource represents the Listbox, with the new "arrangement" of items, I can therefore check if the item is now located at the end, and move it in this case.

唯一的问题是，由于项目被删除，然后移动，它会导致屏幕上闪烁。

The only problem left is that it causes a flicker on the screen, due to the item being dropped and then moved.

我仍然可以使用任何其他（最好的）建议。

I'm still open to any other (best) suggestion.

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