使用 ItemSource 使用 ListView WPF 拖放失败

Question

我有 ListView 和 ItemSource:

public ObservableCollection<MyObject> List;

我的 ListView 装满了好几个东西。

现在我想添加通过 darg 更改我的 ListViewItems 的选项，所以我找到了这个解决方案：https://fxmax.wordpress.com/2010/10/05/wpf/

在我的项目中添加代码后，我只有一个导致崩溃的问题：

private void BeginDrag(MouseEventArgs e)
        {
            ListView listView = this.listView;
            ListViewItem listViewItem = FindAnchestor<ListViewItem>((DependencyObject)e.OriginalSource);

            if (listViewItem == null)
                return;

            // get the data for the ListViewItem
            MyObject name = (MyObject)listView.ItemContainerGenerator.ItemFromContainer(listViewItem);

            //setup the drag adorner.
            InitialiseAdorner(listViewItem);

            //add handles to update the adorner.
            listView.PreviewDragOver += listView_PreviewDragOver;
            listView.DragLeave += listView_DragLeave;
            listView.DragEnter += listView_DragEnter;

            DataObject data = new DataObject("myFormat", name);
            DragDropEffects de = DragDrop.DoDragDrop(this.listView, data, DragDropEffects.Move);

            //cleanup 
            listView.PreviewDragOver -= listView_PreviewDragOver;
            listView.DragLeave -= listView_DragLeave;
            listView.DragEnter -= listView_DragEnter;

            if (_adorner != null)
            {
                AdornerLayer.GetAdornerLayer(listView).Remove(_adorner);
                _adorner = null;
            }
        }

在这一行：

DragDropEffects de = DragDrop.DoDragDrop(this.listView, data, DragDropEffects.Move);

System.InvalidOperationException: 'Operation is not valid while ItemsSource is in use. Access and modify elements with ItemsControl.ItemsSource instead.'

我可以看出这是因为我正在使用 ItemSource 但不知道要更改什么。

有什么建议吗？

Answer 1

从您在其他站点上链接的示例代码开始，我做了一些更改并且能够修复解决方案以使用 ItemsSource。

所做的修改如下： - 在 MainWindow.xaml

            <ListView ItemsSource="{Binding List}"
              x:Name="listView"

- 在 MainWindow.xaml.cs

 private void ListViewDrop(object sender, DragEventArgs e)
    {
        if (e.Data.GetDataPresent("myFormat"))
        {
            MyObject name = e.Data.GetData("myFormat") as MyObject;
            ListViewItem listViewItem = FindAnchestor<ListViewItem>((DependencyObject)e.OriginalSource);
            ObservableCollection<MyObject> myArray = listView.ItemsSource as ObservableCollection<MyObject>;

            if (listViewItem != null && listViewItem.DataContext is MyObject)
            {
                MyObject dropLocation = (MyObject)listViewItem.DataContext;
                int index = myArray.IndexOf(dropLocation);

                if (index >= 0)
                {
                    myArray.Remove(name);
                    myArray.Insert(index, name);
                }
            }
            else
            {
                myArray.Remove(name);
                myArray.Add(name);
            }
        }
    }

...

private void BeginDrag(MouseEventArgs e)
    {
        ListView listView = this.listView;
        ListViewItem listViewItem =
            FindAnchestor<ListViewItem>((DependencyObject)e.OriginalSource);

        if (listViewItem == null)
            return;

        MyObject selectedItem = (MyObject)listViewItem.DataContext;

        //setup the drag adorner.
        InitialiseAdorner(listViewItem);

        //add handles to update the adorner.
        listView.PreviewDragOver += ListViewDragOver;
        listView.DragLeave += ListViewDragLeave;
        listView.DragEnter += ListViewDragEnter;

        DataObject data = new DataObject("myFormat", selectedItem);
        DragDropEffects de = DragDrop.DoDragDrop(this.listView, data, DragDropEffects.Move);

        //cleanup 
        listView.PreviewDragOver -= ListViewDragOver;
        listView.DragLeave -= ListViewDragLeave;
        listView.DragEnter -= ListViewDragEnter;

        if (_adorner != null)
        {
            AdornerLayer.GetAdornerLayer(listView).Remove(_adorner);
            _adorner = null;
        }
    }

更改本身使用 MyObject 的概念作为有效负载，而不是字符串，ObservableCollection 作为您进行更改的数组，而不是 IEnumerable。

希望这能解决您的问题。

使用 ItemSource 使用 ListView WPF 拖放失败

Drag and Drop with ListView WPF failed using ItemSource

wpf

drag

listviewitem