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我有一个名为 的 PictureBox pic，放置在另一个名为的 PictureBox 内picTrack。

我的目标是能够让用户在运行时pic通过拖动来改变它的位置。

这是我到目前为止所拥有的：

    int x_offset = 0; // any better to do this without having a global variable?
    int y_offset = 0;
    void pic_MouseDown(object sender, MouseEventArgs e)
    {
        PictureBox me = (PictureBox)sender;
        x_offset = me.Left - e.X;
        y_offset = me.Top - e.Y;
    }

    void pic_MouseMove(object sender, MouseEventArgs e)
    {
        if (e.Button == System.Windows.Forms.MouseButtons.Left)
        {
            PictureBox me = (PictureBox)sender;
            me.Left = e.X + x_offset; 
            me.Top = e.Y + y_offset;
            picTrack.Invalidate();
        }
    }

此代码仅适用于非常基本的级别。我有两个问题：

1.)picTrack如果用户不松开鼠标按钮，则不会更新。在四处移动pic时可以看到鬼影（就像有尾巴一样）。picpic

2.)pic正在“咯咯地笑”（即在其位置周围左右、上下快速摇晃）。

我应该如何解决这两个问题并创建更流畅的拖放？谢谢。

4

2 回答 2

1

这实际上有效，我之前写过很多拖拽的东西..它可能并不完美，但这应该给你一些可以使用的东西。

    Point dragPoint = Point.Empty;
    bool dragging = false;

    private void pic_MouseDown(object sender, MouseEventArgs e)
    {
        dragging = true;
        dragPoint = new Point(e.X, e.Y);
    }

    private void pic_MouseMove(object sender, MouseEventArgs e)
    {
        if (dragging)
            pic.Location = new Point(pic.Location.X + e.X - dragPoint.X, pic.Location.Y + e.Y - dragPoint.Y);
    }

    private void pic_MouseUp(object sender, MouseEventArgs e)
    {
        dragging = false;
    }

看，如果您正在拖动您自己渲染的本地图片，这是不对的。但是由于您在移动控件后移动它，因此新的移动坐标是相对于控件的。因此，您不需要将 dragPoint 更新到移动的最后一个位置。如果您只是移动正在渲染 OnPaint 的形状/图像，则必须在每次移动时更新拖动点。

如果需要，您可以进行一项改进，即仅在用户将光标移动一定距离 D 时才开始拖动。例如，如下所示：

    Point dragPoint = Point.Empty;
    bool dragging = false;
    bool mouseDown = false;

    private void pic_MouseDown(object sender, MouseEventArgs e)
    {
        mouseDown = true;
        dragPoint = new Point(e.X, e.Y);
    }

    private void pic_MouseMove(object sender, MouseEventArgs e)
    {
        int deltaX = e.X - dragPoint.X;
        int deltaY = e.Y - dragPoint.Y;

        if (!dragging && mouseDown && deltaX * deltaX + deltaY * deltaY > 100)
            dragging = true;

        if (dragging)
            pic.Location = new Point(pic.Location.X + deltaX, pic.Location.Y + deltaY);
    }

    private void pic_MouseUp(object sender, MouseEventArgs e)
    {
        dragging = false;
        mouseDown = false;
    }

它检查用户是否将鼠标移动了 10 像素（100 平方）。

如果您不想要全局，您可以尝试实现自己的行为系统并创建一段可重用的代码，您可以将其附加到您想要移动的东西上。像这样的东西：

public class Behavior<T> where T : class 
{
    public T AssociatedObject
    {
        get;
        private set;
    }

    public Behavior(T associatedObject)
    {
        this.AssociatedObject = associatedObject;
    }

    public virtual void Attach() { }
    public virtual void Detach() { }
}

public class DragBehavior : Behavior<Control>
{
    Point dragPoint = Point.Empty;
    bool dragging = false;
    bool mouseDown = false;

    public DragBehavior(Control c) : base(c)
    {

    }

    public override void Attach()
    {
        AssociatedObject.MouseDown += new MouseEventHandler(control_MouseDown);
        AssociatedObject.MouseMove += new MouseEventHandler(control_MouseMove);
        AssociatedObject.MouseUp += new MouseEventHandler(control_MouseUp);
    }

    private void control_MouseUp(object sender, MouseEventArgs e)
    {
        dragging = false;
        mouseDown = false;
    }

    private void control_MouseMove(object sender, MouseEventArgs e)
    {
        int deltaX = e.X - dragPoint.X;
        int deltaY = e.Y - dragPoint.Y;

        if (mouseDown && deltaX * deltaX + deltaY * deltaY > 100)
            dragging = true;

        if (dragging)
            AssociatedObject.Location = new Point(AssociatedObject.Location.X + deltaX, AssociatedObject.Location.Y + deltaY);
    }

    private void control_MouseDown(object sender, MouseEventArgs e)
    {
        mouseDown = true;
        dragPoint = new Point(e.X, e.Y);
    }

    public override void Detach()
    {
        AssociatedObject.MouseDown -= new MouseEventHandler(control_MouseDown);
        AssociatedObject.MouseMove -= new MouseEventHandler(control_MouseMove);
        AssociatedObject.MouseUp -= new MouseEventHandler(control_MouseUp);
    }
}

public partial class Form1 : Form
{
    DragBehavior dragger;

    public Form1()
    {
        InitializeComponent();
        DoubleBuffered = true;

        dragger = new DragBehavior(pic);
        dragger.Attach();
    }       
}

也许这比“创建一个全局变量”更好（或者更像是在你的表单中创建一个成员变量。=）

于 2012-11-06T06:51:23.703 回答
0

试试这个

int x_offset = 0; // any better to do this without having a global variable?
int y_offset = 0;
private void pic_MouseDown(object sender, MouseEventArgs e)
{
   PictureBox me = (PictureBox)sender;
   x_offset = e.X;
   y_offset = e.Y;
}

private void pic_MouseMove(object sender, MouseEventArgs e)
{
  if (e.Button == System.Windows.Forms.MouseButtons.Left)
  {
     PictureBox me = (PictureBox)sender;
     me.Left = e.X + me.Left - x_offset;
     me.Top = e.Y + me.Top - y_offset;
   }
}
于 2012-11-06T05:56:55.483 回答