C# 在面板周围拖动控件

Question

我正在开发一个允许用户在同一个面板中拖动对象的系统，我经过一些研究发现我应该使用鼠标事件，如 mouse_up、mouse_down 和 mouse_move。

该程序将生成 3 个图片框并允许用户在面板内的每个图片框周围拖动，但我编写的程序无法完美运行，因为当我拖动图片框时，图片框会移动，但不是根据我的鼠标光标位置，它在其他地方，此外，在拖动时，面板中有图片框阴影，我尝试过那些 update()、refresh() 和 invalidate()，但它似乎对我没有用。以下是我的代码，感谢您的帮助

public partial class Form1 : Form
{

    List<PictureBox> pictureBoxList = new List<PictureBox>();
    private bool isDragging = false;

    public Form1()
    {
        InitializeComponent();

        for (int i = 0; i < 3; i++)
        {
            PictureBox picture = new PictureBox
            {
                Name = "pictureBox" + i,
                Size = new Size(20, 20),
                Location = new Point(i * 40, i * 40),
                BorderStyle = BorderStyle.FixedSingle,
                SizeMode = PictureBoxSizeMode.Zoom,
                ImageLocation = "A.jpg"
            };
            pictureBoxList.Add(picture);


            foreach (PictureBox p in pictureBoxList)
            {
                p.MouseDown += new MouseEventHandler(c_MouseDown);
                p.MouseMove += new MouseEventHandler(c_MouseMove);
                p.MouseUp += new MouseEventHandler(c_MouseUp);
                pnlDisplayImage.Controls.Add(p);
                pnlDisplayImage.Refresh();
            }
        }
    }


    void c_MouseDown(object sender, MouseEventArgs e)
    {
        isDragging = true;
    }

    void c_MouseMove(object sender, MouseEventArgs e)
    {

        if (isDragging == true) {
            Control c = sender as Control;
            for (int i = 0; i < pictureBoxList.Count(); i++)
            {
                if (c.Equals(pictureBoxList[i]))
                {
                    pictureBoxList[i].Location = new Point(e.X, e.Y);
                }
            }
        }
    }

    void c_MouseUp(object sender, MouseEventArgs e)
    {
        PictureBox c = sender as PictureBox;
        isDragging = false;
        for (int i = 0; i < pictureBoxList.Count(); i++) { 
            if (c.Equals(pictureBoxList[i])){
                pictureBoxList[i].Location = new Point(e.X, e.Y);
            }
        }
    }

    private void pnlDisplayImage_Paint(object sender, PaintEventArgs e)
    {
        foreach (PictureBox p in pictureBoxList)
        {
            pnlDisplayImage.Controls.Add(p);
        }
    }

}

Answer 1

最后我找到了导致我的程序没有按预期运行的问题。主要问题是我不小心将foreach循环放在了我用来创建pictureBox的for循环中，这个问题导致pictureBox在运行时出现一些阴影效果，因为相同的pictureBox很少。此外，我更改了一些代码，现在它按我的预期运行。以下是我想要回答的代码。

public partial class Form1 : Form
{

    List<PictureBox> pictureBoxList = new List<PictureBox>();
    private bool isDragging = false;
    Point move;

    public Form1()
    {
        InitializeComponent();

        for (int i = 0; i < 3; i++)
        {
            PictureBox picture = new PictureBox
            {
                Name = "pictureBox" + i,
                Size = new Size(20, 20),
                Location = new Point(i * 40, i * 40),
                BorderStyle = BorderStyle.FixedSingle,
                SizeMode = PictureBoxSizeMode.Zoom,
                ImageLocation = "A.jpg"
            };
            pictureBoxList.Add(picture);
        }

        foreach (PictureBox p in pictureBoxList)
        {
                p.MouseDown += new MouseEventHandler(c_MouseDown);
                p.MouseMove += new MouseEventHandler(c_MouseMove);
                p.MouseUp += new MouseEventHandler(c_MouseUp);
                pnlDisplayImage.Controls.Add(p);
                pnlDisplayImage.Refresh();
         }

    }

    void c_MouseDown(object sender, MouseEventArgs e)
    {
        Control c = sender as Control;
        isDragging = true;
        move = e.Location;
    }

    void c_MouseMove(object sender, MouseEventArgs e)
    {

        if (isDragging == true) {
            Control c = sender as Control;
            for (int i = 0; i < pictureBoxList.Count(); i++)
            {
                if (c.Equals(pictureBoxList[i]))
                {
                    pictureBoxList[i].Left += e.X - move.X;
                    pictureBoxList[i].Top += e.Y - move.Y;
                }
            }
        }
    }

    void c_MouseUp(object sender, MouseEventArgs e)
    {
        isDragging = false;
    }
}

Answer 2

尝试类似（它是带有覆盖的自定义控件，但应该很容易转换为事件）：

    private bool _isMoved = false;  // true if move mode on
    private Point _pointMove = new Point(0);    // for moving

    protected override void OnMouseDown(MouseEventArgs e)
    {
        // if left button pressed
        if(e.Button == MouseButtons.Left) 
        {
            _pointMove.X = e.X;
            _pointMove.Y = e.Y;
            _isMoved = true;
            Cursor = Cursors.SizeAll;
            Capture = true;
        }
        base.OnMouseDown (e);
    }

    protected override void OnMouseUp(MouseEventArgs e)
    {
        // if move mode on
        if(_isMoved) 
        {
            _isMoved = false;
            Cursor = Cursors.Default;
            Capture = false;
        }
        base.OnMouseUp (e);
    }

    protected override void OnMouseMove(MouseEventArgs e)
    {
        // if move mode on
        if (_isMoved)
        {
            Left += e.X - _pointMove.X;
            Top += e.Y - _pointMove.Y;
        }
        base.OnMouseMove (e);
    }