C# 在面板周围拖动控件

Posted 2023-05-08

【中文标题】C# 在面板周围拖动控件

【英文标题】：C# drag controls around a panel

【发布时间】：2013-08-22 03:04:26

【问题描述】：

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);
        
    

【参考方案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;
    

【参考方案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);
    

【讨论】：

嗨 Sinatr，感谢您的回答，我尝试将您给定的代码转换为我的案例，它给了我相同的结果，只是鼠标光标改变了。我在想是不是我的 pnlDisplayImage_Paint 事件导致了问题