用鼠标移动实例化的对象（Visual Studio C＃）

Question

Right now if I click a button I create a new picturebox filled with a .png (a car). I wish to move the car with the mouse after it is instantiated and I can't figure out how to do that. I understand (I think) how to drag a picturebox that is already on the screen, but not one that is generated programmically.

public void CreatePatrolCar()
    {
        int picX = Properties.Resources.police.Width;
        int picY = Properties.Resources.police.Height;


        PictureBox pc = new PictureBox();
        pc.Image = Properties.Resources.police;
        pc.Size = new Size(picX / 3, picY / 3);
        pc.SizeMode = PictureBoxSizeMode.StretchImage;
        pc.Location = new Point(100, 100);

        Controls.Add(pc);            
    }

Answer 1

I was just working on this yesterday. I'm not sure if this is the best way but it works. It uses a control + mousedown event to initiate the drag.

When the child control is created I add the mouse event handlers below.

 private void btnNotes_Click(object sender, EventArgs e)
    {
        if (_editor == null)
        {
            _editor = new VimControl();
            _editor.Location = new Point(400, 200);
            _editor.Size = _editor.MinimumSize;
            _editor.vimTextBox.Text = "Hello World!";
            _editor.vimTextBox.MouseDown += HandleMouseDown;
            _editor.vimTextBox.MouseMove += HandleMouseMove;
            _editor.vimTextBox.MouseUp += HandleMouseUp;
            this.SuspendLayout();
            this.Controls.Add(_editor);
            _editor.BringToFront();
            this.ResumeLayout(true);
        }

        _editor.Show();


    }

#region Drag Child
private Point? _mouseDown = null;
private Point? _mouseLast = null;
private Control frame = null;

/// <summary>
/// Control click to begin drag child.
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private void HandleMouseDown(object sender, MouseEventArgs e)
{
    var child = sender as Control;
    Log.Message("Sender: {0}", child == null ? "Unknown" : child.Name);

    Log.Message("{0} MouseDown at ({1}, {2})", e.Button, e.X, e.Y);
    if (e.Button == MouseButtons.Left && (Control.ModifierKeys & Keys.Control) == Keys.Control)
    {
        _mouseDown = e.Location;
        _mouseLast = e.Location;
        frame = FormHelper.FrameControl(_editor.Size, _editor.Location);
        this.Controls.Add(frame);
        frame.BringToFront();
    }
}

private void HandleMouseMove(object sender, MouseEventArgs e)
{
    var child = sender as Control;
    Log.Message("Sender: {0}", child == null ? "Unknown" : child.Name);

    if (child == null) return;

    if (_mouseDown.HasValue)
    {
        Point delta = MyMath.Delta(_mouseLast.Value, e.Location);
        frame.Left = frame.Left + delta.X;
        frame.Top = frame.Top + delta.Y;
        _mouseLast = e.Location;
    }
}

private void HandleMouseUp(object sender, MouseEventArgs e)
{
    var child = sender as Control;
    Log.Message("My {0} MouseUp at ({1}, {2})", e.Button, e.X, e.Y);
    if (e.Button == MouseButtons.Left && _mouseDown.HasValue)
    {
        _mouseDown = null;
        _mouseLast = e.Location;
        this.SuspendLayout();
        {
            child.Location = frame.Location;
            this.Controls.Remove(frame);
            frame.Dispose();
            frame = null;
        }
        this.ResumeLayout(true);
        child.Show();
    }
}
#endregion

The frame control is just an empty user control that stands in for the child during the drag. It makes the drag much smoother.

public static UserControl FrameControl(Size size, Point location)
    {
        UserControl frame = new UserControl();
        frame.Location =  location;
        frame.Size =  size;
        frame.BorderStyle = BorderStyle.Fixed3D;
        frame.BackColor = Color.Transparent;

        return frame;
    }

Delta Helper function

public static Point Delta(Point p1, Point p2)
{
    return new Point(p2.X - p1.X, p2.Y - p1.Y);
}