using System.Collections;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Input;
using System.Windows.Media;
namespace Waaagh.Behaviors {
sealed public class ItemsDraggable {
#region Drag Drop Data Format String
static readonly string DraggableDataFormat = "DraggableData";
static readonly string DraggableCollectionFormat = "DraggableCollection";
#endregion
#region Enabled
static public bool GetEnabled(DependencyObject obj) {
return (bool)obj.GetValue(EnabledProperty);
}
static public void SetEnabled(DependencyObject obj, bool value) {
obj.SetValue(EnabledProperty, value);
}
static public readonly DependencyProperty EnabledProperty =
DependencyProperty.RegisterAttached("Enabled", typeof(bool), typeof(ItemsDraggable),
new PropertyMetadata(false, OnEnabledChanged));
static private void OnEnabledChanged(DependencyObject sender, DependencyPropertyChangedEventArgs args) {
if (sender is ItemsControl itemsControl == false) {
throw new InvalidOperationException("The attached control is not an 'ItemsControl'.");
}
itemsControl.AllowDrop = false;
itemsControl.MouseMove -= ItemsDraggable_MouseMove;
itemsControl.DragEnter -= ItemsDraggable_DragEnter;
itemsControl.DragOver -= ItemsDraggable_DragOver;
itemsControl.DragLeave -= ItemsDraggable_DragLeave;
itemsControl.Drop -= ItemsDraggable_Drop;
if (GetEnabled(itemsControl) == true) {
itemsControl.AllowDrop = true;
itemsControl.MouseMove += ItemsDraggable_MouseMove;
itemsControl.DragEnter += ItemsDraggable_DragEnter;
itemsControl.DragOver += ItemsDraggable_DragOver;
itemsControl.DragLeave += ItemsDraggable_DragLeave;
itemsControl.Drop += ItemsDraggable_Drop;
}
}
public static Func<object, Type, IList?> GetQueryTargetCollection(DependencyObject obj) {
return (Func<object, Type, IList?>)obj.GetValue(QueryTargetCollectionProperty);
}
public static void SetQueryTargetCollection(DependencyObject obj, Func<object, Type, IList?> value) {
obj.SetValue(QueryTargetCollectionProperty, value);
}
public static readonly DependencyProperty QueryTargetCollectionProperty =
DependencyProperty.RegisterAttached("QueryTargetCollection", typeof(Func<object, Type, IList?>), typeof(ItemsDraggable), new PropertyMetadata(null));
#endregion
#region Drag Drop Event
static private void ItemsDraggable_MouseMove(object sender, MouseEventArgs args) {
if (args.LeftButton != MouseButtonState.Pressed) {
return;
}
if (sender is ItemsControl source == false) {
return;
}
if (source.ItemsSource is IList == false) {
return;
}
if (GetElement(source, args.GetPosition(source)) is Control sourceControl == false) {
return;
}
if (GetParent(sourceControl) is ItemsControl sourceItemsControl == false) {
return;
}
DataObject data = new DataObject();
data.SetData(DraggableDataFormat, sourceControl.DataContext);
data.SetData(DraggableCollectionFormat, sourceItemsControl.ItemsSource);
DragDrop.DoDragDrop(sourceItemsControl, data, DragDropEffects.Move);
}
static private void ItemsDraggable_DragEnter(object sender, DragEventArgs args) {
}
static private void ItemsDraggable_DragOver(object sender, DragEventArgs args) {
}
static private void ItemsDraggable_DragLeave(object sender, DragEventArgs args) {
}
static private void ItemsDraggable_Drop(object sender, DragEventArgs args) {
if (args.Effects == DragDropEffects.None) {
return;
}
if (sender is ItemsControl target == false) {
return;
}
// 获取 放置目标
if (GetElement(target, args.GetPosition(target)) is Control targetControl == false) {
return;
}
if (GetParent(targetControl) is ItemsControl targetItemsControl == false) {
return;
}
if (targetItemsControl.ItemsSource is IList targetCollection == false) {
return;
}
// 获取 拖拽源
object? sourceData = args.Data.GetData(DraggableDataFormat) as object;
IList? sourceCollection = args.Data.GetData(DraggableCollectionFormat) as IList;
if (sourceData == null || sourceCollection == null) {
return;
}
// 判断 集合元素类型
object? targetData = targetControl.DataContext;
if (CheckCollectionElementType(sourceCollection, targetCollection) == false) {
IList? collection = GetQueryTargetCollection(targetItemsControl)?.Invoke(targetControl.DataContext, sourceData.GetType());
if (collection == null || CheckCollectionElementType(sourceCollection, collection) == false) {
return;
}
targetCollection = collection;
targetData = null; // 置 targetData 为 null, 尝试将 sourceData 添加到 targetCollection 末尾
}
// 执行 拖拽影响
DoDragDropEffects(args.Effects, sourceCollection, sourceData, targetCollection, targetData);
}
#endregion
#region Drag Drop Effects
static private void DoDragDropEffects(DragDropEffects effects, IList sourceCollection, object sourceData, IList targetCollection, object? targetData) {
if (sourceCollection == null || sourceData == null || targetCollection == null) {
return;
}
if (object.ReferenceEquals(sourceData, targetData)) {
return;
}
switch (effects) {
case DragDropEffects.Scroll: {
break;
}
case DragDropEffects.All: {
break;
}
case DragDropEffects.Copy: {
break;
}
case DragDropEffects.Move: {
DoMoveEffect(sourceCollection, sourceData, targetCollection, targetData);
break;
}
case DragDropEffects.Link: {
break;
}
default: {
break;
}
}
}
static private void DoMoveEffect(IList sourceCollection, object sourceData, IList targetCollection, object? targetData) {
int oldIndex = sourceCollection.IndexOf(sourceData);
int newIndex = targetCollection.IndexOf(targetData);
if (newIndex == -1) {
newIndex = targetCollection.Count - 1;
}
if (object.ReferenceEquals(sourceCollection, targetCollection)) {
if (oldIndex == newIndex) {
return;
}
// 同个集合, 移除元素后下标可能变化
if (oldIndex < newIndex) {
newIndex -= 1;
}
}
sourceCollection.RemoveAt(oldIndex);
targetCollection.Insert(newIndex + 1, sourceData);
}
#endregion
#region Helper
static private bool GetDragDropEventSource(ref ItemsControl parent, out Control child, Func<IInputElement, Point> getPosition) {
if (parent != null) {
ItemContainerGenerator generator = parent.ItemContainerGenerator;
for (int i = generator.Items.Count - 1; i >= 0; --i) {
if (generator.ContainerFromIndex(i) is Control control == false) {
continue;
}
Point position = getPosition(control);
if (position.X < 0 || position.X > control.ActualWidth ||
position.Y < 0 || position.Y > control.ActualHeight) {
continue;
}
if (control is ContentControl) {
child = control;
return true;
}
if (control is ItemsControl itemsControl) {
ItemsControl prevParent = parent;
parent = itemsControl;
if (GetDragDropEventSource(ref parent, out child, getPosition) == false) {
child = parent;
parent = prevParent;
}
return true;
}
}
}
child = default!;
return false;
}
static private Control? GetElement(ItemsControl source, Point point) {
if (GetItemContainerType(source) is Type type == false) {
return null;
}
DependencyObject? dp = source.InputHitTest(point) as DependencyObject;
while (dp != null) {
if (dp.GetType().Equals(type)) {
break;
}
dp = VisualTreeHelper.GetParent(dp);
}
return dp as Control;
}
static private ItemsControl? GetParent(Control control) {
for (DependencyObject dp = VisualTreeHelper.GetParent(control); dp != null; dp = VisualTreeHelper.GetParent(dp)) {
if (dp is ItemsControl parent && parent.ItemContainerGenerator.ContainerFromItem(control.DataContext) != null) {
return parent;
}
}
return null;
}
static private Type? GetItemContainerType(ItemsControl source) {
if (source == null) {
return null;
}
if (source is ListView) {
return typeof(ListViewItem);
}
else if (source is ListBox) {
return typeof(ListBoxItem);
}
else if (source is TreeView || source is TreeViewItem) {
return typeof(TreeViewItem);
}
// else if (source is GridView) {
// return typeof(GridViewColumn);
// }
if (source.Items.Count > 0) {
return source.ItemContainerGenerator.ContainerFromIndex(0)?.GetType();
}
return null;
}
static private bool CheckCollectionElementType(IList collection1, IList collection2) {
return collection1.GetType().GetGenericArguments()[0] == collection2.GetType().GetGenericArguments()[0];
}
#endregion
}
}