WPF C＃：通过拖放重新排列列表框中的项目

Question

我试图找出如何通过鼠标拖动来上下移动预先填充的列表框中的项目。

我从microsoft的api看过Control.DoDragDrop方法，但我仍然无法做任何事情。

我很感激任何帮助，因为我是视觉工作室环境的新手。

Answer 1

我尝试使用observablecollection创建一个，看看

    ObservableCollection<Emp> _empList = new ObservableCollection<Emp>();

    public Window1()
    {
        InitializeComponent();

        _empList .Add(new Emp("1", 22));
        _empList .Add(new Emp("2", 18));
        _empList .Add(new Emp("3", 29));
        _empList .Add(new Emp("4", 9));
        _empList .Add(new Emp("5", 29));
        _empList .Add(new Emp("6", 9));
        listbox1.DisplayMemberPath = "Name";
        listbox1.ItemsSource = _empList;

        Style itemContainerStyle = new Style(typeof(ListBoxItem));
        itemContainerStyle.Setters.Add(new Setter(ListBoxItem.AllowDropProperty, true));
        itemContainerStyle.Setters.Add(new EventSetter(ListBoxItem.PreviewMouseLeftButtonDownEvent, new MouseButtonEventHandler(s_PreviewMouseLeftButtonDown)));
        itemContainerStyle.Setters.Add(new EventSetter(ListBoxItem.DropEvent, new DragEventHandler(listbox1_Drop)));
        listbox1.ItemContainerStyle = itemContainerStyle;
    }

拖放过程

    void s_PreviewMouseLeftButtonDown(object sender, MouseButtonEventArgs e)
    {

        if (sender is ListBoxItem)
        {
            ListBoxItem draggedItem = sender as ListBoxItem;
            DragDrop.DoDragDrop(draggedItem, draggedItem.DataContext, DragDropEffects.Move);
            draggedItem.IsSelected = true;
        }
    }

    void listbox1_Drop(object sender, DragEventArgs e)
    {
        Emp droppedData = e.Data.GetData(typeof(Emp)) as Emp;
        Emp target = ((ListBoxItem)(sender)).DataContext as Emp;

        int removedIdx = listbox1.Items.IndexOf(droppedData);
        int targetIdx = listbox1.Items.IndexOf(target);

        if (removedIdx < targetIdx)
        {
            _empList.Insert(targetIdx + 1, droppedData);
            _empList.RemoveAt(removedIdx);
        }
        else
        {
            int remIdx = removedIdx+1;
            if (_empList.Count + 1 > remIdx)
            {
                _empList.Insert(targetIdx, droppedData);
                _empList.RemoveAt(remIdx);
            }
        }
    }

注意：

• 实施中有一件事很糟糕，因为它使用了PreviewMouseLeftButtonDown事件，被拖动的项目看起来没有被选中
• 并且为了更容易实现，放置目标是列表框项而不是列表框本身 - 可能需要更好的解决方案

Answer 2

使用dnr3的答案我创建了具有固定选择问题的版本。

Window1.xaml

<Window x:Class="ListBoxReorderDemo.Window1"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="ListBoxReorderDemo" Height="300" Width="300"
        WindowStartupLocation="CenterScreen">
    <Grid>
        <ListBox x:Name="listBox"/>
    </Grid>
</Window>

Window1.xaml.cs

using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Text;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;

namespace ListBoxReorderDemo
{
    public class Item
    {
        public string Name { get; set; }
        public Item(string name)
        {
            this.Name = name;
        }
    }

    public partial class Window1 : Window
    {
        private Point _dragStartPoint;

        private T FindVisualParent<T>(DependencyObject child)
            where T : DependencyObject
        {
            var parentObject = VisualTreeHelper.GetParent(child);
            if (parentObject == null)
                return null;
            T parent = parentObject as T;
            if (parent != null)
                return parent;
            return FindVisualParent<T>(parentObject);
        }

        private IList<Item> _items = new ObservableCollection<Item>();

        public Window1()
        {
            InitializeComponent();

            _items.Add(new Item("1"));
            _items.Add(new Item("2"));
            _items.Add(new Item("3"));
            _items.Add(new Item("4"));
            _items.Add(new Item("5"));
            _items.Add(new Item("6"));

            listBox.DisplayMemberPath = "Name";
            listBox.ItemsSource = _items;

            listBox.PreviewMouseMove += ListBox_PreviewMouseMove;

            var style = new Style(typeof(ListBoxItem));
            style.Setters.Add(new Setter(ListBoxItem.AllowDropProperty, true));
            style.Setters.Add(
                new EventSetter(
                    ListBoxItem.PreviewMouseLeftButtonDownEvent,
                    new MouseButtonEventHandler(ListBoxItem_PreviewMouseLeftButtonDown)));
            style.Setters.Add(
                    new EventSetter(
                        ListBoxItem.DropEvent, 
                        new DragEventHandler(ListBoxItem_Drop)));
            listBox.ItemContainerStyle = style;
        }

        private void ListBox_PreviewMouseMove(object sender, MouseEventArgs e)
        {
            Point point = e.GetPosition(null);
            Vector diff = _dragStartPoint - point;
            if (e.LeftButton == MouseButtonState.Pressed &&
                (Math.Abs(diff.X) > SystemParameters.MinimumHorizontalDragDistance ||
                    Math.Abs(diff.Y) > SystemParameters.MinimumVerticalDragDistance))
            {
                var lb = sender as ListBox;
                var lbi = FindVisualParent<ListBoxItem>(((DependencyObject)e.OriginalSource));
                if (lbi != null)
                {
                    DragDrop.DoDragDrop(lbi, lbi.DataContext, DragDropEffects.Move);
                }
            }
        }
        private void ListBoxItem_PreviewMouseLeftButtonDown(object sender, MouseButtonEventArgs e)
        {
            _dragStartPoint = e.GetPosition(null);
        }

        private void ListBoxItem_Drop(object sender, DragEventArgs e)
        {
            if (sender is ListBoxItem)
            {
                var source = e.Data.GetData(typeof(Item)) as Item;
                var target = ((ListBoxItem)(sender)).DataContext as Item;

                int sourceIndex = listBox.Items.IndexOf(source);
                int targetIndex = listBox.Items.IndexOf(target);

                Move(source, sourceIndex, targetIndex);
            }
        }

        private void Move(Item source, int sourceIndex, int targetIndex)
        {
            if (sourceIndex < targetIndex)
            {
                _items.Insert(targetIndex + 1, source);
                _items.RemoveAt(sourceIndex);
            }
            else
            {
                int removeIndex = sourceIndex + 1;
                if (_items.Count + 1 > removeIndex)
                {
                    _items.Insert(targetIndex, source);
                    _items.RemoveAt(removeIndex);
                }
            }
        }
    }
}

支持泛型和数据绑定的版本。

Window1.xaml

<Window x:Class="ListBoxReorderDemo.Window1"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:local="clr-namespace:ListBoxReorderDemo"
        Title="ListBoxReorderDemo" Height="300" Width="300"
        WindowStartupLocation="CenterScreen">
    <Grid>
        <local:ItemDragAndDropListBox x:Name="listBox" ItemsSource="{Binding}">
            <ListBox.ItemTemplate>
                <DataTemplate>
                    <TextBlock Text="{Binding Name}"/>
                </DataTemplate>
            </ListBox.ItemTemplate>
        </local:ItemDragAndDropListBox>
    </Grid>
</Window>

Window1.xaml.cs

using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Text;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;

namespace ListBoxReorderDemo
{
    public class DragAndDropListBox<T> : ListBox 
        where T : class
    {
        private Point _dragStartPoint;

        private P FindVisualParent<P>(DependencyObject child) 
            where P : DependencyObject
        {
            var parentObject = VisualTreeHelper.GetParent(child);
            if (parentObject == null)
                return null;

            P parent = parentObject as P;
            if (parent != null)
                return parent;

            return FindVisualParent<P>(parentObject);
        }

        public DragAndDropListBox()
        {
            this.PreviewMouseMove += ListBox_PreviewMouseMove;

            var style = new Style(typeof(ListBoxItem));

            style.Setters.Add(new Setter(ListBoxItem.AllowDropProperty, true));

            style.Setters.Add(
                new EventSetter(
                    ListBoxItem.PreviewMouseLeftButtonDownEvent,
                    new MouseButtonEventHandler(ListBoxItem_PreviewMouseLeftButtonDown)));

            style.Setters.Add(
                    new EventSetter(
                        ListBoxItem.DropEvent, 
                        new DragEventHandler(ListBoxItem_Drop)));

            this.ItemContainerStyle = style;
        }

        private void ListBox_PreviewMouseMove(object sender, MouseEventArgs e)
        {
            Point point = e.GetPosition(null);
            Vector diff = _dragStartPoint - point;
            if (e.LeftButton == MouseButtonState.Pressed &&
                (Math.Abs(diff.X) > SystemParameters.MinimumHorizontalDragDistance ||
                    Math.Abs(diff.Y) > SystemParameters.MinimumVerticalDragDistance))
            {
                var lb = sender as ListBox;
                var lbi = FindVisualParent<ListBoxItem>(((DependencyObject)e.OriginalSource));
                if (lbi != null)
                {
                    DragDrop.DoDragDrop(lbi, lbi.DataContext, DragDropEffects.Move);
                }
            }
        }

        private void ListBoxItem_PreviewMouseLeftButtonDown(object sender, MouseButtonEventArgs e)
        {
            _dragStartPoint = e.GetPosition(null);
        }

        private void ListBoxItem_Drop(object sender, DragEventArgs e)
        {
            if (sender is ListBoxItem)
            {
                var source = e.Data.GetData(typeof(T)) as T;
                var target = ((ListBoxItem)(sender)).DataContext as T;

                int sourceIndex = this.Items.IndexOf(source);
                int targetIndex = this.Items.IndexOf(target);

                Move(source, sourceIndex, targetIndex);
            }
        }

        private void Move(T source, int sourceIndex, int targetIndex)
        {
            if (sourceIndex < targetIndex)
            {
                var items = this.DataContext as IList<T>;
                if (items != null)
                {
                    items.Insert(targetIndex + 1, source);
                    items.RemoveAt(sourceIndex);
                }
            }
            else
            {
                var items = this.DataContext as IList<T>;
                if (items != null)
                {
                    int removeIndex = sourceIndex + 1;
                    if (items.Count + 1 > removeIndex)
                    {
                        items.Insert(targetIndex, source);
                        items.RemoveAt(removeIndex);
                    }
                }
            }
        }
    }

    public class Item
    {
        public string Name { get; set; }
        public Item(string name)
        {
            this.Name = name;
        }
    }

    public class ItemDragAndDropListBox : DragAndDropListBox<Item> { }

    public partial class Window1 : Window
    {
        private IList<Item> _items = new ObservableCollection<Item>();

        public Window1()
        {
            InitializeComponent();

            _items.Add(new Item("1"));
            _items.Add(new Item("2"));
            _items.Add(new Item("3"));
            _items.Add(new Item("4"));
            _items.Add(new Item("5"));
            _items.Add(new Item("6"));

            listBox.DataContext = _items;
        }
    }
}

Answer 3

我建议使用名为GongSolutions.WPF.DragDrop的拖放行为。它允许使用附加属性设置器的MVVM样式用例启用它，不需要在视图中隐藏代码。您应该查看链接以获取一个简单示例。

Answer 4

我接受了dnr3的回答并将其修改为在XAML中实现。同样的结果，只是喜欢在XAML而不是在代码隐藏中做我能做的事。

代替代码隐藏：

UserManager

把它放在XAML中：

Style itemContainerStyle = new Style(typeof(ListBoxItem));
itemContainerStyle.Setters.Add(new Setter(AllowDropProperty, true));
itemContainerStyle.Setters.Add(new EventSetter(PreviewMouseLeftButtonDownEvent, new MouseButtonEventHandler(s_PreviewMouseLeftButtonDown)));
itemContainerStyle.Setters.Add(new EventSetter(DropEvent, new DragEventHandler(listbox1_Drop)));
listbox1.ItemContainerStyle = itemContainerStyle;

这是放置在XAML代码隐藏中的鼠标处理程序。

<Window.Resources>
    <Style x:Key="ListBoxDragDrop" TargetType="{x:Type ListBoxItem}">
        <Setter Property="AllowDrop" Value="true"/>
        <EventSetter Event="PreviewMouseMove" Handler="s_PreviewMouseMoveEvent"/>
        <EventSetter Event="Drop" Handler="listbox1_Drop"/>
    </Style>
</Window.Resources>
<Grid>
    <ListBox x:Name="listbox1" ItemContainerStyle="{StaticResource ListBoxDragDrop}" HorizontalAlignment="Left" Height="299" Margin="10,10,0,0" VerticalAlignment="Top" Width="224"/>
</Grid>

Answer 5

修复代码：

private void listbox1_Drop(object sender, DragEventArgs e)
{
    if (sender is ListBoxItem)
    {
        Emp droppedData = e.Data.GetData(typeof(Emp)) as Emp;
        Emp target = ((ListBoxItem)(sender)).DataContext as Emp;

        int removedIdx = listbox1.Items.IndexOf(droppedData);
        int targetIdx = listbox1.Items.IndexOf(target);

        if (removedIdx < targetIdx)
        {
            _empList.Insert(targetIdx + 1, droppedData);
            _empList.RemoveAt(removedIdx);
        }
        else
        {
            int remIdx = removedIdx + 1;
            if (_empList.Count + 1 > remIdx)
            {
                _empList.Insert(targetIdx, droppedData);
                _empList.RemoveAt(remIdx);
            }
        }
    }
}

Answer 6

这对我非常感谢。特别是泛型版本。

我做了以下修改：

因为我没有设置ListBox的DataContext（只是ItemsSource），所以我使用

var items = this.ItemsSource as IList<T>;

中的

。

在“移动”结束时，我补充道：

this.SelectedItem = source;

因为我希望用户将移动的项目作为当前选择。

Answer 7

基于WiesławŠoltés对 dnr3 答案的修改，我将其抽象为易于重用的类，以便您可以设置多个仅包含几行代码的列表。我还添加了一项功能，该功能可以使每个项目在两种背景颜色之间交替显示，以方便查看（尽管您可以随意删除此功能）。

F.Y.I：对不起，如果您是'var'的爱好者，但我绝对不是，那些被我的IDE删除了，我也不想将它们放回原处。当然，这不会改变程序的实际行为，反而应该改善编译时间，所以..赢了！ ：p

这是课程：

/// <typeparam name="IT">The item type to be stored in this list</typeparam>
internal class ReorderableList<IT> where IT : class
{
    private readonly SolidColorBrush m_alternator1, m_alternator2; // Background colours for the list items to alternate between
    private readonly ListBox m_ListBox; // The target ListBox we're modifying
    private readonly string m_displayMemberPath; // The name of the member in to display 
    private readonly IList<IT> m_items = new ObservableCollection<IT>();
    private Point m_cursorStartPos;

    /// <summary>
    /// Initializes the list (this must be done after components are initialized and loaded!).
    /// </summary>
    /// <param name="resourceProvider">Pass 'this' for this parameter</param>
    /// <param name="listBox">The target ListBox control to modify</param>
    /// <param name="displayMemberPath">The name of the member in the generic type contained in this list, to be displayed</param>
    public ReorderableList(ListBox listBox, string displayMemberPath, SolidColorBrush alternator1, SolidColorBrush alternator2)
    {
        m_ListBox = listBox;
        m_displayMemberPath = displayMemberPath;
        m_alternator1 = alternator1;
        m_alternator2 = alternator2;

        Initialize();
    }

    private void Initialize()
    {
        // Set the list box's items source and tell it what member in the IT class to use for the display name
        // Add an event handler for preview mouse move

        m_ListBox.DisplayMemberPath = m_displayMemberPath;
        m_ListBox.ItemsSource = m_items;
        m_ListBox.PreviewMouseMove += OnListPreviewMouseMove;

        // Create the item container style to be used by the listbox
        // Add mouse event handlers to the style

        Style style = new Style(typeof(ListBoxItem));
        style.Setters.Add(new Setter(UIElement.AllowDropProperty, true));
        style.Setters.Add(new EventSetter(UIElement.PreviewMouseLeftButtonDownEvent, new MouseButtonEventHandler(OnListPreviewMouseLeftButtonDown)));
        style.Setters.Add(new EventSetter(UIElement.DropEvent, new DragEventHandler(OnListDrop)));

        // Add triggers to alternate the background colour of each element based on its alternation index
        // (Remove this, as well as the two SolidColorBrush resources if you don't want this feature)

        Trigger trigger1 = new Trigger()
        {
            Property = ItemsControl.AlternationIndexProperty,
            Value = 0
        };

        Setter setter1 = new Setter()
        {
            Property = Control.BackgroundProperty,
            Value = m_alternator1
        };

        trigger1.Setters.Add(setter1);
        style.Triggers.Add(trigger1);

        Trigger trigger2 = new Trigger()
        {
            Property = ItemsControl.AlternationIndexProperty,
            Value = 1
        };

        Setter setter2 = new Setter()
        {
            Property = Control.BackgroundProperty,
            Value = m_alternator2
        };

        trigger2.Setters.Add(setter2);
        style.Triggers.Add(trigger2);

        // Set the item container style

        m_ListBox.ItemContainerStyle = style;
    }

    /// <summary>
    /// Adds an item to the list. If [ignoreDuplicates] is false and the item is already in the list,
    /// the item won't be added.
    /// </summary>
    /// <param name="item">The item to add</param>
    /// <param name="ignoreDuplicates">Whether or not to add the item regardless of whether it's already in the list</param>
    /// <returns>Whether or not the item was added</returns>
    public bool Add(IT item, bool ignoreDuplicates = true)
    {
        if (!ignoreDuplicates && Contains(item)) return false;

        m_items.Add(item);
        return true;
    }

    /// <summary>
    /// Removes an item from the list.
    /// </summary>
    /// <param name="item">The item to remove</param>
    /// <returns>Whether or not the item was removed from the list. This will be false if the item was not in the list to begin with.</returns>
    public bool Remove(IT item)
    {
        if (Contains(item)) return false;

        m_items.Remove(item);
        return true;
    }

    /// <summary>
    /// Returns whether or not the list contains the given item.
    /// </summary>
    /// <param name="item">The item to check for</param>
    /// <returns>Whether or not the list contains the given item.</returns>
    public bool Contains(IT item)
    {
        return m_items.Contains(item);
    }

    private void OnListPreviewMouseLeftButtonDown(object sender, MouseButtonEventArgs e)
    {
        m_cursorStartPos = e.GetPosition(null);
    }

    private void OnListPreviewMouseMove(object sender, MouseEventArgs e)
    {
        Point currentCursorPos = e.GetPosition(null);
        Vector cursorVector = m_cursorStartPos - currentCursorPos;

        if (e.LeftButton == MouseButtonState.Pressed
            &&(Math.Abs(cursorVector.X) > SystemParameters.MinimumHorizontalDragDistance
            || Math.Abs(cursorVector.Y) > SystemParameters.MinimumVerticalDragDistance))
        {
            ListBoxItem targetItem = FindVisualParent<ListBoxItem>(((DependencyObject)e.OriginalSource));
            if (targetItem != null)
            {
                DragDrop.DoDragDrop(targetItem, targetItem.DataContext, DragDropEffects.Move);
            }
        }
    }

    private void OnListDrop(object sender, DragEventArgs e)
    {
        if (sender is ListBoxItem item)
        {
            IT source = e.Data.GetData(typeof(IT)) as IT;
            IT target = item.DataContext as IT;

            int sourceIndex = m_ListBox.Items.IndexOf(source);
            int targetIndex = m_ListBox.Items.IndexOf(target);

            Move(source, sourceIndex, targetIndex);
        }
    }

    private void Move(IT source, int sourceIndex, int targetIndex)
    {
        if (sourceIndex < targetIndex)
        {
            m_items.Insert(targetIndex + 1, source);
            m_items.RemoveAt(sourceIndex);
        }
        else
        {
            int removeIndex = sourceIndex + 1;
            if (m_items.Count + 1 > removeIndex)
            {
                m_items.Insert(targetIndex, source);
                m_items.RemoveAt(removeIndex);
            }
        }
    }

    private T FindVisualParent<T>(DependencyObject child) where T : DependencyObject
    {
        DependencyObject parentObject = VisualTreeHelper.GetParent(child);
        if (parentObject == null) return null;
        if (parentObject is T parent) return parent;

        return FindVisualParent<T>(parentObject);
    }
}

这是一个示例IT（项目类型）类（与原始答案相同）：

public class ExampleItem
{
    public string Name { get; set; }

    public ExampleItem(string name)
    {
        Name = name;
    }
}

最后，用法：

public partial class MainWindow : Window
{
    private readonly ReorderableList<ExampleItem> ExampleList;

    public MainWindow()
    {
        InitializeComponent();

        ExampleList = new ReorderableList<ExampleItem>(myXamlListBoxControl, "Name",
            FindResource("AlternatingBG1") as SolidColorBrush,
            FindResource("AlternatingBG2") as SolidColorBrush);

        ExampleList.Add(new ExampleItem("Test Item 1"));
        ExampleList.Add(new ExampleItem("Test Item 2"));
        ExampleList.Add(new ExampleItem("Test Item 3"));
        ExampleList.Add(new ExampleItem("Test Item 4"));
        ExampleList.Add(new ExampleItem("Test Item 5"));
        ExampleList.Add(new ExampleItem("Test Item 6"));
    }
}