拖放图片框消失

Question

我的代码有问题。我正在尝试在我的表单上拖放图片，但是当我移动选定的图片框时，当我离开组框时它会丢失。它就这样消失了。

public partial class Form1 : Form
{
    int x_offset = 0; // any better to do this without having a global variable?
    int y_offset = 0;

    PictureBox dpb = new PictureBox();
    public Form1()
    {
        InitializeComponent();

        this.WindowState = FormWindowState.Maximized;
        this.AllowDrop = true;
        this.pictureBox1.MouseDown += pictureBox1_MouseDown;
        this.pictureBox2.MouseDown += pictureBox2_MouseDown;
    }

    private void pictureBox1_MouseDown(object sender, MouseEventArgs e)
    {
        PictureBox me = (PictureBox)sender;
        x_offset = e.X;
        y_offset = e.Y;

    }

    private void pictureBox1_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;
        }
    }

Answer 1

您的 PictureBox 正在被父级（即 GroupBox）剪裁。您可以修复层次结构（查看->其他窗口->文档大纲）。

此外，通常最好使用标准拖放功能，如下所述：http://social.msdn.microsoft.com/Forums/en-US/92cad3ba-dd05-4aa9-ad44-411051407d57/drag-and-drop-picturebox-to-picturebox-in-c?forum=csharplanguage。这将处理所有拖放特殊情况。为了更改标准光标，请将 Cursor.Current 设置为光标，由 CreateCursor(myBitmap) 返回。注意：在某些情况下，CreateCursor 可能会失败，因此请确保提供标准游标的回退。

Answer 2

您的PictureBox 有一个GroupBox 作为其Parent，在winforms 和许多其他UI 技术中，您不能在其父控件之外呈现子控件。在使用您的代码之前，您可能需要执行以下操作：

pictureBox1.Parent = this;//set your Form as Parent of the pictureBox1
pictureBox1.BringToFront();//Ensure your pictureBox1 is on top.

如果您的要求是将pictureBox1 从GroupBox 拖放到另一个控件上，使其成为pictureBox1 的新Parent，您可以尝试以下代码：

    Point downPoint;
    //MouseDown event handler for your pictureBox1
    private void pictureBox1_MouseDown(object sender, MouseEventArgs e){
        downPoint = e.Location;
        pictureBox1.Parent = this;
        pictureBox1.BringToFront();
    }
    //MouseMove event handler for your pictureBox1
    private void pictureBox1_MouseMove(object sender, MouseEventArgs e){
        if (e.Button == MouseButtons.Left) {
            pictureBox1.Left += e.X - downPoint.X;
            pictureBox1.Top += e.Y - downPoint.Y;
        }
    }
    //MouseUp event handler for your pictureBox1
    private void pictureBox1_MouseUp(object sender, MouseEventArgs e) {
        Control c = GetChildAtPoint(new Point(pictureBox1.Left - 1, pictureBox1.Top));
        if (c == null) c = this;
        Point newLoc = c.PointToClient(pictureBox1.Parent.PointToScreen(pictureBox1.Location));
        pictureBox1.Parent = c;
        pictureBox1.Location = newLoc;
    }