wpf在.net4.0和4.5的情况下，触摸屏测试时不触法drop事件了

Question

<Window x:Class="DragDrop.Window1"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="clr-namespace:DragDrop"
    Title="Window1" Height="400" Width="500">
    <Window.Resources>
        <DataTemplate x:Key="listBoxTemplate" DataType="{x:Type local:DataItem}">
            <TextBlock Text="{Binding Header}"/>
        </DataTemplate>
        <HierarchicalDataTemplate x:Key="treeViewTemplate" DataType="{x:Type local:DataItem}" 
                                  ItemsSource="{Binding Items}">
            <TextBlock Text="{Binding Header}"/>
        </HierarchicalDataTemplate>
    </Window.Resources>
    <Grid x:Name="mTopLevelGrid">
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="*"/>
            <ColumnDefinition Width="10"/>
            <ColumnDefinition Width="*"/>
        </Grid.ColumnDefinitions>
        <ListBox x:Name="mListBox" Grid.Column="0" ItemsSource="{Binding Source={x:Static local:Data.Instance}, Path=ListBoxItems}" ItemTemplate="{StaticResource listBoxTemplate}"/>
        <TreeView x:Name="mTreeView" Grid.Column="2" ItemsSource="{Binding Source={x:Static local:Data.Instance}, Path=TreeViewItems}" ItemTemplate="{StaticResource treeViewTemplate}"
                  AllowDrop="True" DragOver="OnDragOver" Drop="OnDrop"/>
    </Grid>
</Window>

后台代码：

using System;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;

namespace DragDrop
{
    public partial class Window1 : Window
    {
        public Window1()
        {
            InitializeComponent();
            AttachEvents();
        }

        private void AttachEvents()
        {
            mListBox.PreviewMouseMove += OnPreviewListBoxMouseMove;
            mListBox.QueryContinueDrag += OnQueryContinueDrag;
        }

        private void OnPreviewListBoxMouseMove(object sender, MouseEventArgs e)
        {
            if (Mouse.LeftButton != MouseButtonState.Pressed)
                return;

            Point pos = e.GetPosition(mListBox);
            HitTestResult result = VisualTreeHelper.HitTest(mListBox, pos);
            if (result == null)
                return;

            ListBoxItem listBoxItem = Utils.FindVisualParent<ListBoxItem>(result.VisualHit); // Find your actual visual you want to drag
            if (listBoxItem == null || listBoxItem.Content != mListBox.SelectedItem || !(mListBox.SelectedItem is DataItem))
                return;

            DragDropAdorner adorner = new DragDropAdorner(listBoxItem);
            mAdornerLayer = AdornerLayer.GetAdornerLayer(mTopLevelGrid); // Window class do not have AdornerLayer
            mAdornerLayer.Add(adorner);

            DataItem dataItem = listBoxItem.Content as DataItem;
            DataObject dataObject = new DataObject(dataItem.Clone());
            // Here, we should notice that dragsource param will specify on which 
            // control the drag&drop event will be fired
            System.Windows.DragDrop.DoDragDrop(mListBox, dataObject, DragDropEffects.Copy);

            mStartHoverTime = DateTime.MinValue;
            mHoveredItem = null;
            mAdornerLayer.Remove(adorner);
            mAdornerLayer = null;
            e.Handled = false;
        }

        private void OnQueryContinueDrag(object sender, QueryContinueDragEventArgs e)
        {
            mAdornerLayer.Update();

            UpdateTreeViewExpandingState();
        }

        private void OnDragOver(object sender, DragEventArgs e)
        {
            e.Effects = DragDropEffects.None;

            Point pos = e.GetPosition(mTreeView);
            HitTestResult result = VisualTreeHelper.HitTest(mTreeView, pos);
            if (result == null)
                return;

            TreeViewItem selectedItem = Utils.FindVisualParent<TreeViewItem>(result.VisualHit);
            if (selectedItem != null)
                selectedItem.IsSelected = true;

            e.Effects = DragDropEffects.Copy;
        }

        private void OnDrop(object sender, DragEventArgs e)
        {
            Point pos = e.GetPosition(mTreeView);
            HitTestResult result = VisualTreeHelper.HitTest(mTreeView, pos);
            if (result == null)
                return;

            TreeViewItem selectedItem = Utils.FindVisualParent<TreeViewItem>(result.VisualHit);
            if (selectedItem == null)
                return;

            DataItem parent = selectedItem.Header as DataItem;
            DataItem dataItem = e.Data.GetData(typeof(DataItem)) as DataItem;
            if (parent != null && dataItem != null)
                parent.Items.Add(dataItem);
        }

        private void UpdateTreeViewExpandingState()
        {
            Win32.POINT point = new Win32.POINT();
            if (Win32.GetCursorPos(ref point))
            {
                Point pos = new Point(point.X, point.Y);
                pos = mTreeView.PointFromScreen(pos);
                HitTestResult result = VisualTreeHelper.HitTest(mTreeView, pos);
                if (result != null)
                {
                    TreeViewItem selectedItem = Utils.FindVisualParent<TreeViewItem>(result.VisualHit);
                    if (selectedItem != null)
                    {
                        if (mHoveredItem != selectedItem)
                        {
                            mHoveredItem = selectedItem;
                            mStartHoverTime = DateTime.Now;
                        }
                        else
                        {
                            if (mHoveredItem.Items.Count > 0 && !mHoveredItem.IsExpanded &&
                                DateTime.Now - mStartHoverTime > TimeSpan.FromSeconds(2))
                                mHoveredItem.IsExpanded = true;
                        }
                    }
                }
            }
        }

        DateTime mStartHoverTime = DateTime.MinValue;
        TreeViewItem mHoveredItem = null;
        AdornerLayer mAdornerLayer = null;
    }

    internal static class Utils
    {
        public static T FindVisualParent<T>(DependencyObject obj) where T : class
        {
            while (obj != null)
            {
                if (obj is T)
                    return obj as T;

                obj = VisualTreeHelper.GetParent(obj);
            }

            return null;
        }
    }
}

以上代码在.net3.5的情况下正常拖拽。.net4.0和4.5拖拽没有反应。

---

wjm

Answer 1

楼主，在OnDrop上打断点，能走到这个事件吗？我这边没有设备，也没办法测试！

Answer 2

不行，.net3.5就可以，代码不变，就是切换.net版本。

---

wjm