Develop Reference

Drag and Drop Windows Forms: Controls disappear after dragging

I need to drag labels between the panels. But when I'm trying to drop a label even within the initial panel, it disappears. Here is the code of the methods I use:
private void label1_MouseDown(object sender, MouseEventArgs e)
{
if (e.Button == MouseButtons.Left)
DoDragDrop(sender, DragDropEffects.All);
}
private void panel_DragEnter(object sender, DragEventArgs e)
{
e.Effect = DragDropEffects.All;
}
private void panel_DragDrop(object sender, DragEventArgs e)
{
Label src = e.Data.GetData(typeof(Label)) as Label;
src.Location = PointToClient(new Point(e.X, e.Y));
}
AllowDrop is enabled for the panels. Why do the labels disappear and how can I fix it?

The Label is still contained by the Form, so it is simply going behind the Panel.
Either...
(1) Bring the Label to the Front:
private void panel1_DragDrop(object sender, DragEventArgs e)
{
Label src = e.Data.GetData(typeof(Label)) as Label;
src.Location = this.PointToClient(new Point(e.X, e.Y));
src.BringToFront();
}
or,
(2) Make the Panel contain the Label, and adjust the coordinates to the Panel's client coord system:
private void panel1_DragDrop(object sender, DragEventArgs e)
{
Panel pnl = sender as Panel;
Label src = e.Data.GetData(typeof(Label)) as Label;
src.Location = pnl.PointToClient(new Point(e.X, e.Y));
pnl.Controls.Add(src);
}

Drag and dropping a button (Button won't follow)

I'm having a bit of trouble making drag and drop a button in a panel and panel to recognize it and display Message with buttons name
So far I managed the part of dragging and dropping and recognizing however I'm missing the visual style of dragging, when I press with mouse it will just sit on the same place, it won't follow cursor. How do I make it follow the mouse?
public Form1()
{
InitializeComponent();
panel1.AllowDrop = true;
panel1.DragEnter += panel_DragEnter;
panel1.DragDrop += panel_DragDrop;
button1.MouseDown += button1_MouseDown;
}
private void button1_MouseDown(object sender, System.Windows.Forms.MouseEventArgs e)
{
button1.DoDragDrop(button1.Text, DragDropEffects.Copy | DragDropEffects.Move);
button1.Location= new Point(e.X, e.Y);
}
private void panel_DragEnter(object sender, System.Windows.Forms.DragEventArgs e)
{
e.Effect = DragDropEffects.Move;
if (e.Data.GetDataPresent(DataFormats.Text))
e.Effect = DragDropEffects.Copy;
else
e.Effect = DragDropEffects.None;
}
private void panel_DragDrop(object sender, System.Windows.Forms.DragEventArgs e)
{
MessageBox.Show(e.Data.GetData(DataFormats.Text).ToString());
}

You'll have to keep in mind that the DoDragDrop method doesn't return the Position you dropped the object. The DragDrop event handles that.
To move the control while you're dragging you use the DragOver event of the panel. In the implementation you need to compensate for the fact that the X and Y coordinates in the EventArgs are Screen based while you need Clientbased coordinates to correctly position the control. The PointToClient is instrumental in that:
private void panel_DragOver(object sender, DragEventArgs e)
{
if (e.Data.GetDataPresent(typeof(Button).FullName))
{
var draggedButton = (Button)e.Data.GetData(typeof(Button).FullName);
var screenpos = new Point(e.X, e.Y);
var clientPos = panel1.PointToClient(screenpos);
// calc offset
draggedButton.Location = new Point(
clientPos.X + panel1.Left,
clientPos.Y + panel1.Top);
}
}
Notice that your Data now contains the actual Button, instead of only the text. This makes that you can dragdrop multiple buttons, not only button1.
Your DragDrop event should now look like this:
private void panel_DragDrop(object sender, System.Windows.Forms.DragEventArgs e)
{
if (e.Data.GetDataPresent(typeof(Button).FullName))
{
var draggedButton = (Button)e.Data.GetData(typeof(Button).FullName);
MessageBox.Show(draggedButton.Text);
var screenpos = new Point(e.X, e.Y);
var clientPos = panel1.PointToClient(screenpos);
draggedButton.Location = new Point(
clientPos.X + panel1.Left,
clientPos.Y + panel1.Top);
}
}
And DragEnter only slightly changed so it could handle the Button control instead of the text:
private void panel_DragEnter(object sender, System.Windows.Forms.DragEventArgs e)
{
e.Effect = DragDropEffects.Move;
if (e.Data.GetDataPresent(typeof(Button).FullName)) // button
e.Effect = DragDropEffects.Copy;
else
e.Effect = DragDropEffects.None;
}
And finally to get it all started and wired up the constructor code and the MouseDown implementation of the button:
public Form1()
{
InitializeComponent();
panel1.AllowDrop = true;
panel1.DragEnter += panel_DragEnter;
panel1.DragDrop += panel_DragDrop;
panel1.DragOver += panel_DragOver;
button1.MouseDown += button1_MouseDown;
}
private void button1_MouseDown(object sender, System.Windows.Forms.MouseEventArgs e)
{
button1.DoDragDrop(button1, DragDropEffects.Copy | DragDropEffects.Move);
}

Moving a control within another control's visible area

I have a PictureBox that is inside a TabPage, and of course this TabPage is part of a TabView and this TabView is inside a Form. I want users be able to move this picture box within the tab page. For this I am using the MouseDown, MouseMove and MouseUp events of the picture box:
private void pictureBoxPackageView_MouseDown(object sender, MouseEventArgs e)
{
if (!_mapPackageIsMoving)
{
_mapPackageIsMoving = true;
}
}
private void pictureBoxPackageView_MouseMove(object sender, MouseEventArgs e)
{
if(_mapPackageIsMoving)
{
pictureBoxPackageView.Location = MousePosition; //This is not exact at all!
return;
}
//Some other code for some other stuff when picturebox is not moving...
}
private void pictureBoxPackageView_MouseUp(object sender, MouseEventArgs e)
{
if (_mapPackageIsMoving)
{
_mapPackageIsMoving = false; //Mouse button is up, end moving!
return;
}
}
But my problem lies in the MouseMove event. As soon as I move mouse after button down, the picture box jumps out of tab page's visible area.
I need to know how to handle the move only within the rectangle of the tab page, and if picture box is being dragged out of tab view's visible area, it shouldn't move anymore unless user brings the mouse inside the tab view's visible rectangle.
Any helps/tips will be appriciated!

You need a variable to hold the original position of the PictureBox:
Modified from a HansPassant answer:
private Point start = Point.Empty;
void pictureBoxPackageView_MouseUp(object sender, MouseEventArgs e) {
_mapPackageIsMoving = false;
}
void pictureBoxPackageView_MouseMove(object sender, MouseEventArgs e) {
if (_mapPackageIsMoving) {
pictureBoxPackageView.Location = new Point(
pictureBoxPackageView.Left + (e.X - start.X),
pictureBoxPackageView.Top + (e.Y - start.Y));
}
}
void pictureBoxPackageView_MouseDown(object sender, MouseEventArgs e) {
start = e.Location;
_mapPackageIsMoving = true;
}

How to move PictureBox in C#?

i have used this code to move picture box on the pictureBox_MouseMove event
pictureBox.Location = new System.Drawing.Point(e.Location);
but when i try to execute the picture box flickers and the exact position cannot be identified. can you guys help me with it. I want the picture box to be steady...

You want to move the control by the amount that the mouse moved:
Point mousePos;
private void pictureBox1_MouseDown(object sender, MouseEventArgs e) {
mousePos = e.Location;
}
private void pictureBox1_MouseMove(object sender, MouseEventArgs e) {
if (e.Button == MouseButtons.Left) {
int dx = e.X - mousePos.X;
int dy = e.Y - mousePos.Y;
pictureBox1.Location = new Point(pictureBox1.Left + dx, pictureBox1.Top + dy);
}
}
Note that this code does not update the mousePos variable in MouseMove. Necessary since moving the control changes the relative position of the mouse cursor.

You have to do several things
Register the start of the moving operation in MouseDown and remember the start location of the mouse.
In MouseMove see if you are actually moving the picture. Move by keeping the same offset to the upper left corner of the picture box, i.e. while moving, the mouse pointer should always point to the same point inside the picture box. This makes the picture box move together with the mouse pointer.
Register the end of the moving operation in MouseUp.
private bool _moving;
private Point _startLocation;
private void pictureBox1_MouseDown(object sender, MouseEventArgs e)
{
_moving = true;
_startLocation = e.Location;
}
private void pictureBox1_MouseUp(object sender, MouseEventArgs e)
{
_moving = false;
}
private void pictureBox1_MouseMove(object sender, MouseEventArgs e)
{
if (_moving) {
pictureBox1.Left += e.Location.X - _startLocation.X;
pictureBox1.Top += e.Location.Y - _startLocation.Y;
}
}

Try to change SizeMode property from AutoSize to Normal

C# - Moving a control to the mouse's position

I am trying to get a control to follow the cursor when the user clicks and drag the control. The problem is that 1.) the control doesn't go to the mouse's position, and 2.) the control flickers and flies all over the place. I've tried a few different methods of doing this, but all so far have failed.
I've tried:
protected override void OnMouseDown(MouseEventArgs e)
{
while (e.Button == System.Windows.Forms.MouseButtons.Left)
{
this.Location = e.Location;
}
}
and
protected override void OnMouseMove(MouseEventArgs e)
{
while (e.Button == System.Windows.Forms.MouseButtons.Left)
{
this.Location = e.Location;
}
}
but neither of these work. Any help is appreciated, and thanks in advance!

Here's how to do it:
private Point _Offset = Point.Empty;
protected override void MouseDown(object sender, MouseEventArgs e)
{
if (e.Button == MouseButtons.Left)
{
_Offset = new Point(e.X, e.Y);
}
}
protected override void MouseMove(object sender, MouseEventArgs e)
{
if (_Offset != Point.Empty)
{
Point newlocation = this.Location;
newlocation.X += e.X - _Offset.X;
newlocation.Y += e.Y - _Offset.Y;
this.Location = newlocation;
}
}
protected override void MouseUp(object sender, MouseEventArgs e)
{
_Offset = Point.Empty;
}
_Offset is used here for two purposes: keeping track of where the mouse was on the control when you initially clicked it, and also keeping track of whether the mouse button is down or not (so that the control doesn't get dragged when the mouse cursor goes over it and the button isn't down).
You definitely don't want to switch the ifs in this code to whiles, as it will make a difference.

there are mistakes in the answer 1
1.Set mouse handlers to control ,not to form
like button1_MouseMove
2.do not use this vector,but your control instead(Point newlocation = button1.Location;)
3.you do not need to override handlers.
in my test after these changes button(or other control) moves fine.
Chigook

Try this to move the object according to the mouse's position and the code below given is to gather the mouse's move path and the location saved in the arraylist to obtain the path where mouse point is moving. You have to declare the arraylist globally.
private void panel1_MouseMove(object sender, MouseEventArgs e)
{
if (e.Button == MouseButtons.Left)
{
ArrayList inList = new ArrayList();
inList.Add(e.X);
inList.Add(e.Y);
list.Add(inList);
}
}
When the user clicks the button the control has to move in the path that the user dragged in the screen
private void button1_Click_2(object sender, EventArgs e)
{
foreach (ArrayList li in list)
{
pic_trans.Visible = true;
pic_trans.Location = new Point(Convert.ToInt32(li[0]), Convert.ToInt32(li[1]));
pic_trans.Show();
}
}

private Point ptMouseDown=new Point();
protected override void MouseDown(object sender, MouseEventArgs e)
{
if (e.Button == MouseButtons.Left)
{
ptMouseDown = new Point(e.X, e.Y);
}
}
protected override void MouseMove(object sender, MouseEventArgs e)
{
if (_Offset != Point.Empty)
{
Pointf[] ptArr=new Pointf[]{this.Location};
Point Diff=new Point(e.X-ptMouseDown.X,e.Y-ptMouseDown.Y);
Matrix mat=new Matrix();
mat.Translate(Diff.X,Diff.Y);
mat.TransFromPoints(ptArr);
this.Location=ptArr[0];
}
}
protected override void MouseUp(object sender, MouseEventArgs e)
{
_Offset = Point.Empty;
}