C＃单击源检测

Question

I have a GroupBox that has multiple controls, specifically 4 PictureBoxes .

These are pieces of an image puzzle. Please note that the number of images can change. I want to allow a drag and drop effect to each of them. To mark the source and the destination I did the following:

foreach (var box in boxes)
{
    box.DragEnter += new DragEventHandler(box_DragEnter);
    box.MouseDown += new MouseEventHandler(box_MouseDown);
    box.DragDrop += new DragEventHandler(box_DragDrop);
    box.AllowDrop = true;
}

When a box is clicked it will be marked to a global variable (that will be the source) and when a box raises the DragDrop event that will be the destination.

As I previously mentioned, since the number of the boxes can be changed I do not want to add separate methods as handlers for each event.

My issue here is that I do not know how to "detect" which box has raised what event.

Example:

*If I press on the left-top image I want to know that I pressed on it to mark the source (let's say global picSource = 1) and if I drop on right-bottom image I want to know that as a destination (picDestination = 4). All that must occur in the handlers. *

Tests:

• Adding a parent panel (same size as the GroupBox) with a Click event & doing a comparison between a Point issued with the X&Y provided by the event handler and a rectangle designated with the X,Y, width, height of the panel.
• Adding handlers to the GroupBox (does not work either)

Notes:

• eX and eY refer to the position of the mouse

  void box_MouseDown(object sender, MouseEventArgs e)

• The purpose of this is to switch boxes (source <--> destination)

Answer 1

You can just detect puzzle element by mouse's coordinates in the controls container's MouseDown and MouseUp event as follows:

public partial class PuzzleForm : Form
{
    private readonly Image[,] Images;
    private readonly int Nx;
    private readonly int Ny;
    private int sourceIndexX;
    private int sourceIndexY;
    private int destinationIndexX;
    private int destinationIndexY;

    private PuzzleForm()
    {
        SetStyle(ControlStyles.AllPaintingInWmPaint | ControlStyles.ResizeRedraw, true);
        InitializeComponent();
    }

    public PuzzleForm(Image[,] images)
        : this()
    {
        Images = images;
        Nx = Images.GetLength(0);
        Ny = Images.GetLength(1);
    }

    protected override void OnPaint(PaintEventArgs e)
    {
        base.OnPaint(e);

        using (Graphics g = e.Graphics)
        {
            for (int j = 0; j < Ny; j++)
                for (int i = 0; i < Nx; i++)
                {
                    Rectangle rect = new Rectangle(ClientSize.Width * i / Nx, ClientSize.Height * j / Ny, ClientSize.Width / Nx - 1, ClientSize.Height / Ny - 1);
                    g.DrawImage(Images[i, j], rect);
                }
        }
    }

    protected override void OnMouseDown(MouseEventArgs e)
    {
        base.OnMouseDown(e);

        if (e.Button != MouseButtons.Left)
            return;

        sourceIndexX = e.X * Nx / ClientSize.Width;
        sourceIndexY = e.Y * Ny / ClientSize.Height;

        Cursor = Cursors.Hand;
    }

    protected override void OnMouseUp(MouseEventArgs e)
    {
        base.OnMouseUp(e);

        if (e.Button != MouseButtons.Left)
            return;

        destinationIndexX = e.X * Nx / ClientSize.Width;
        destinationIndexY = e.Y * Ny / ClientSize.Height;

        Cursor = Cursors.Default;

        if (sourceIndexX != destinationIndexX || sourceIndexY != destinationIndexY)
        {
            swapImages();
            MessageBox.Show(String.Format("From [{0}, {1}] to [{2}, {3}]", sourceIndexX, sourceIndexY, destinationIndexX, destinationIndexY));
        }
    }

    private void swapImages()
    {
        Image tmp = Images[sourceIndexX, sourceIndexY];
        Images[sourceIndexX, sourceIndexY] = Images[destinationIndexX, destinationIndexY];
        Images[destinationIndexX, destinationIndexY] = tmp;
        Invalidate();
    }
}

Usage:

Image[,] images = new Image[2, 2];
// Fill array with images:
images[0, 0] = Bitmap.FromFile(@"..."); 
images[0, 1] = Bitmap.FromFile(@"...");
images[1, 0] = Bitmap.FromFile(@"...");
images[1, 1] = Bitmap.FromFile(@"...");

PuzzleForm puzzleForm = new PuzzleForm(images);
// Show form or whatever you want.
...