在两个WPF控件之间拖放-我需要根据第二个控件内的位置更改鼠标图标

Question

I have two WPF controls. One is a TreeView and the other is a graph control. I have dragging and dropping working between them. When I drag from the TreeView control to the graph control and drop something it works as I want it to. The mouse cursor has the dragging drop look to it during this. However I want to change the mouse cursor (to something that points up) if the user points the mouse to the top half of the graph control. If the user goes to the bottom of the graph control then I want the cursor to go back to the original dragging drop look.

I thought I could use the GiveFeedback event with the 1st control but that doesn't return the graph object to me.

I can provide code if needed but I don't think it would be helpful. I do have a method called MouseNearTop(Graph g, DragEventArgs e) that returns a bool true if the mouse is in the top half of the grid ad false if on the bottom half.

UPDATE: I tried using the Mouse.OverrideCursor property but that seems to change the mouse after you release the button. I tried again using the static class DragDrop but that throws exceptions and still doesn't work.

This is for the code for my second attempt:

namespace WpfApplication11
{
/// <summary>
/// Interaction logic for MainWindow.xaml
/// </summary>
public partial class MainWindow : Window
{
    public MainWindow()
    {
        InitializeComponent();
    }

    private bool pointingUp = true;

    private void Rectangle_DragOver(object sender, DragEventArgs e)
    {
        currentPoint = e.GetPosition(MyRectangle);

        if ((currentPoint.X > 0) && (currentPoint.X < MyRectangle.ActualWidth) && (currentPoint.Y > 0) && (currentPoint.Y < (MyRectangle.ActualHeight / 2)))
        {
            if (!pointingUp)
            {
                //Mouse.OverrideCursor = Cursors.UpArrow;'
                try
                {
                    DragDrop.DoDragDrop(MyRectangle1, MyRectangle1, DragDropEffects.Copy);
                }
                catch
                {

                }
                pointingUp = true;
            }
        }
        else
        {
            if (pointingUp)
            {
                //Mouse.OverrideCursor = null;
                try
                {
                    DragDrop.DoDragDrop(MyRectangle1, MyRectangle1, DragDropEffects.Move);
                }
                catch
                {

                }
                pointingUp = false;
            }
        }
    }

    Point currentPoint = new Point();

    private void MyRectangle1_MouseMove(object sender, MouseEventArgs e)
    {
        System.Media.SystemSounds.Beep.Play();
        if (e.LeftButton == MouseButtonState.Pressed)
        {
            //if (FileTree.SelectedItem == null)
            //{
            //  return;
            //}

            //var node = FileTree.SelectedItem as TreeViewNode;
            // && (node.TableName.Equals("Ttmp", StringComparison.InvariantCultureIgnoreCase))
            //if ((node.Items.Count == 0) && !(node.TableName == "Temp" || node.NodeDisplayName.EqualsAtLeastOne(StringComparison.InvariantCultureIgnoreCase, "DiFR", "DSFR")))
            //{
                var mousePos = e.GetPosition(null);
                var diff = _startPoint - mousePos;

                if (Math.Abs(diff.X) > SystemParameters.MinimumHorizontalDragDistance
                    || Math.Abs(diff.Y) > SystemParameters.MinimumVerticalDragDistance)
                {
                    DragDrop.DoDragDrop(MyRectangle1, MyRectangle1, DragDropEffects.Move);
                }
            //}
        }
    }

    private Point _startPoint;

    private void MyRectangle1_PreviewMouseLeftButtonDown(object sender, MouseButtonEventArgs e)
    {
        _startPoint = e.GetPosition(null);
    }

    private void MyRectangle_GiveFeedback(object sender, GiveFeedbackEventArgs e)
    {
        //Point p = e.GetPosition(MyRectangle);



    }

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


}
}

Answer 1

I've used a Rectangle for demo purposes, but I think this should work OK with whatever graph you're using.

private void MyRectangle_DragOver(object sender, DragEventArgs e)
{
    Point p = e.GetPosition(MyRectangle);
    if ((p.X > 0) && (p.X < MyRectangle.ActualWidth) && (p.Y > 0) && (p.Y < (MyRectangle.ActualHeight / 2)))
    {
        Mouse.OverrideCursor = Cursors.UpArrow;
    }
    else
    {
        Mouse.OverrideCursor = null;
    }
}

Answer 2

I figured a solution.

In the object I am dragging the data into I have this method:

        private void ObjectDraggingInto_DragOver(object sender, DragEventArgs e)
    {
        if (ObjectDraggingFrom.DragDroppingOn)
        {
            ObjectDraggingFrom.MoveUpCursor = MouseNearTop(sender, e)
                ? true
                : false;
        }
    }

Then here is the code from the object that I started dragging from:

    public static bool MoveUpCursor = false;
    public static bool DragDroppingOn = false;

    private void ObjectDraggingFrom_GiveFeedback(object sender, GiveFeedbackEventArgs e)
    {
        if (MoveUpCursor)
        {
            e.UseDefaultCursors = false;
            Mouse.SetCursor(Cursors.UpArrow);
        }
        else
        {
            e.UseDefaultCursors = true;
        }

        e.Handled = true;
    }


        private void ObjectDragging_Drop(object sender, DragEventArgs e)
    {
        if (e.Data.GetDataPresent(DataFormats.FileDrop))
        {
            ((DataExploreViewModel)DataContext).ImportDraggedAndDroppedFiles((string[])e.Data.GetData(DataFormats.FileDrop));
        }

        DragDroppingOn = false;
    }



        private void ObjectDraggingFrom_MouseMove(object sender, MouseEventArgs e)
    {

        if (e.LeftButton == MouseButtonState.Pressed)
        {
            if (myData.SelectedItem == null)
            {
                return;
            }


                var mousePos = e.GetPosition(null);
                var diff = _startPoint - mousePos;

                if (Math.Abs(diff.X) > SystemParameters.MinimumHorizontalDragDistance
                    || Math.Abs(diff.Y) > SystemParameters.MinimumVerticalDragDistance)
                {
                    DragDroppingOn = true;
                    DragDrop.DoDragDrop(FileTree, data, DragDropEffects.Move | DragDropEffects.Copy);
                }
            }
    }

So this will change the mouse drag cursor to a up arrow when you are in the upper half of the object you are dragging to. Otherwise the cursor will look like the normal drag cursor.