Develop Reference

C# Drag and Drop in Listview doesn't work with Groups

I have a Listview with Drag and Drop codes working well.
However, after i add groups to it, the Drag and Drop codes are run, but the outcome is not what the codes used to behave.
Dropped items were only added to the tail of its group.
Why? and how to get it work properly with groups?
The Drag and Drop procedures are given herebelow:
private void lvQ_DragDrop(object sender, DragEventArgs e)
{
int targetIndex = lvQ.InsertionMark.Index;
if (targetIndex == -1)
return;
if (lvQ.InsertionMark.AppearsAfterItem)
targetIndex++;
ListViewItem draggedItem = (ListViewItem)e.Data.GetData(typeof(ListViewItem));
if (targetIndex == 0 && lvQ.Items.OfType<ListViewItem>().FirstOrDefault()?.SubItems[1].Text == "FF")
{
lvQ.InsertionMark.Index = -1;
}
else
{
lvQ.BeginUpdate();
lvQ.Items.Insert(targetIndex, (ListViewItem)draggedItem.Clone());
lvQ.Items.Remove(draggedItem);
lvQ.EndUpdate();
ShowTXFrameStr();
}
}
private void lvQ_DragEnter(object sender, DragEventArgs e)
{
e.Effect = e.AllowedEffect;
}
private void lvQ_DragLeave(object sender, EventArgs e)
{
lvQ.InsertionMark.Index = -1;
}
private void lvQ_DragOver(object sender, DragEventArgs e)
{
Point ptScreen = new(e.X, e.Y);
Point pt = lvQ.PointToClient(ptScreen);
int targetIndex = lvQ.InsertionMark.NearestIndex(pt);
if (targetIndex > -1)
{
Rectangle itemBounds = lvQ.GetItemRect(targetIndex);
lvQ.InsertionMark.AppearsAfterItem = pt.Y > itemBounds.Top + (itemBounds.Height / 2);
}
lvQ.InsertionMark.Index = targetIndex;
}
private void lvQ_ItemDrag(object sender, ItemDragEventArgs e)
{
lvQ.DoDragDrop(e.Item, DragDropEffects.Move);
}

Custom scrollbar for panel does not scroll smoothly

customBtn1 is the custom scrollbar. The below code sample works, but the scrolling action is jittery and stuttery. It does not scroll smoothly. Any idea why this could be happening and how to fix it?
int PreviousBarLoc;
private void MainForm_Load(object sender, EventArgs e)
{
PreviousBarLoc= customBtn1.Location.Y;
}
//move the scrollbar up and down when the user drags it
private void customBtn1_MouseDown(object sender, MouseEventArgs e)
{
if (e.Button == System.Windows.Forms.MouseButtons.Left)
{ MouseDownLocation = e.Location; }
}
private Point MouseDownLocation;
private void customBtn1_MouseMove(object sender, MouseEventArgs e)
{
if (e.Button == MouseButtons.Left)
{
customBtn1.Top = e.Y + customBtn1.Top - MouseDownLocation.Y;
}
}
//scroll the panel
private void customBtn1_LocationChanged(object sender, EventArgs e)
{
int locDifference = customBtn1.Location.Y - PreviousBarLoc;
if (steamSrvListPnl.VerticalScroll.Value + locDifference <= 255 && steamSrvListPnl.VerticalScroll.Value + locDifference >= 0)
{
steamSrvListPnl.VerticalScroll.Value += locDifference;
}
PreviousBarLoc= customBtn1.Location.Y;
}

Your deltas are not quite right. The way it is currently written, if you drag the mouse down and then start dragging back up, it will not scroll back up because your current e.Y is still below the original MouseDownLocation.Y. I'm not entirely sure of your setup, but below is an example of how to get smooth scrolling to work when the left mouse button is pressed and dragged on a button:
private int _prevY = 0;
private bool _mouseDown = false;
private void button1_MouseDown(object sender, MouseEventArgs e)
{
if (e.Button == MouseButtons.Left)
{
_mouseDown = true;
_prevY = e.Y;
}
}
private void button1_MouseMove(object sender, MouseEventArgs e)
{
if (_mouseDown)
{
panel1.VerticalScroll.Value = Math.Max(panel1.VerticalScroll.Minimum, Math.Min(panel1.VerticalScroll.Maximum, panel1.VerticalScroll.Value + e.Y - _prevY));
_prevY = e.Y;
}
}
private void button1_MouseUp(object sender, MouseEventArgs e)
{
if (_mouseDown)
{
_mouseDown = false;
_prevY = 0;
}
}

Dragging Objects in C#

I am attempting to drag Music Notes vertically, up and down a Music Staff. However, rather than a constant drag, I would like the music notes to only be allowed to be dragged onto particular intervals (only specific y-coordinates). For example, in a vertical line, a music note can be dragged on to coordinates (0,0), (0,5) or (0,10).
Below is my relevant code:
private Point MouseDownLocation;
private void Note_MouseDown(object sender, MouseEventArgs e)
{
foreach (MusicNote mn in panel2.Controls.OfType<MusicNote>())
{
if (sender == mn)
{
if (e.Button == MouseButtons.Left)
{
MouseDownLocation = e.Location;
}
}
}
}
private void Note_MouseMove(object sender, MouseEventArgs e)
{
foreach(MusicNote mn in panel2.Controls.OfType<MusicNote>())
{
if (sender == mn)
{
if (e.Button == MouseButtons.Left)
{
mn.Top = e.Y + mn.Top - MouseDownLocation.Y;
}
}
}
}
Any help is appreciated. Thank you!

Basically, you need to check if you drag up or drag down
You should want to check the MouseDown.X and compare it to the MouseUp.X (or Y if you want to check vertical direction as well). It is important to note that (0, 0) is the upper left of your screen. So you need to compare the X position from mouse down event to the mouse up event.
here's an example with one label that moves up and down in steps of 10
private void label1_MouseDown(object sender, MouseEventArgs e)
{
if (e.Button == System.Windows.Forms.MouseButtons.Left)
{
if (label1.Location.Y > 0 && label1.Location.Y < panel1.Size.Height) // not the most accurate way, but you get the idea
{
mPointDown = new Point(e.X, e.Y);
}
}
}
private void label1_MouseUp(object sender, MouseEventArgs e)
{
bool movedUp, movedDown;
if (e.Y == mPointDown.Y)
{
movedUp = movedDown = false;
}
else
{
movedUp = e.Y < mPointDown.Y;
movedDown = !movedUp;
}
if (movedDown)
{
label1.Location = new Point(label1.Location.X, label1.Location.Y + 10);
}
else if (movedUp)
{
label1.Location = new Point(label1.Location.X, label1.Location.Y - 10);
}
}
private void label1_MouseMove(object sender, MouseEventArgs e)
{
mouseDownPoint = e.Location;
}

Dragging and dropping between two wpf controls - I need the mouse icon to change depending on location inside 2nd control

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;
}
}
}

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;
}
}

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.

Move form relative to location clicked

I have a form which can be moved when the user clicks and drags in a border area. The implementations I've seen all lock to the current mouse position, so that when the form is moved, the form jumps so that the mouse is in the upper-left corner. I'd like to change it so that it behaves like a normal windows form, and the form stays at the same position relative to the mouse when moved. My current code looks like this:
Point locationClicked;
bool isMouseDown = false;
private void Form1_MouseDown(object sender, MouseEventArgs e)
{
isMouseDown = true;
locationClicked = new Point(e.Location.X, e.Location.Y);
}
private void Form1_MouseUp(object sender, MouseEventArgs e)
{
isMouseDown = false;
}
private void Form1_MouseMove(object sender, MouseEventArgs e)
{
if (isMouseDown && targetCell == new Point(-1, -1) && (mouseLocation.X < margin.X || mouseLocation.Y < margin.Y ||
mouseLocation.X > margin.X + cellSize.Width * gridSize.Width ||
mouseLocation.Y > margin.Y + cellSize.Height * gridSize.Height))
{
this.Location = new Point(e.Location.X - locationClicked.X, e.Location.Y - locationClicked.Y);
}
}
When I drag the window, it behaves similarly to what I want. The form flickers between two locations on the screen, one of which moves at about half the rate of the mouse. Is there a way I can fix this?

Try this out...
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
Point locationClicked;
bool dragForm = false;
private void Form1_MouseDown(object sender, MouseEventArgs e)
{
if (e.Button == System.Windows.Forms.MouseButtons.Left)
{
locationClicked = new Point(e.Location.X, e.Location.Y);
if (isMouseDown && targetCell == new Point(-1, -1) && (mouseLocation.X < margin.X || mouseLocation.Y < margin.Y ||
mouseLocation.X > margin.X + cellSize.Width * gridSize.Width ||
mouseLocation.Y > margin.Y + cellSize.Height * gridSize.Height))
{
dragForm = true;
}
}
}
private void Form1_MouseMove(object sender, MouseEventArgs e)
{
if (dragForm)
{
this.Location = new Point(this.Location.X + (e.X - locationClicked.X), this.Location.Y + (e.Y - locationClicked.Y));
}
}
private void Form1_MouseUp(object sender, MouseEventArgs e)
{
dragForm = false;
}
}