XtraTabControl（DEV中选项卡）分页实现拖拽 效果

用到的命名空间是：

    using DevExpress.XtraTab;
    using DevExpress.XtraTab.ViewInfo;

用到的变量:

    private Rectangle rectDragBoxFromMouseDown;
    private bool isDragging = false;
    private Point dragOffset = Point.Empty;

创建所用到的函数:

    private void CalcRectDragBox(int x, int y)
    {
        // Remember the point where the mouse down occurred. The DragSize indicates
        // the size that the mouse can move before a drag event should be started.
        Size dragSize = SystemInformation.DragSize;
        // Create a rectangle using the DragSize, with the mouse position being
        // at the center of the rectangle.
        rectDragBoxFromMouseDown = new Rectangle(new Point((int)x - (dragSize.Width / 2), (int)y - (dragSize.Height / 2)), dragSize);
    }
    private int FindIndex(XtraTabPage page)
    {
        int i = 0;
        while (i < xtcMain.TabPages.Count)
        {
            if (xtcMain.TabPages[i].Equals(page))
            {
                return i;
            }
            i += 1;
        }
        return -1;
    }

在 DragOver 事件中的code：

    XtraTabHitInfo hinfo = default(XtraTabHitInfo);
    XtraTabPage hoverTab = default(XtraTabPage);
    XtraTabPage dragTab = default(XtraTabPage);
    XtraTabPage selTab = default(XtraTabPage);
    XtraTabPage repTab = default(XtraTabPage);
    //
    int itemDragIndex = 0;
    int dropLocationIndex = 0;
    //
    // get the tab we are hovering over.
    hinfo = xtcMain.CalcHitInfo(xtcMain.PointToClient(new Point(e.X, e.Y)));
    //
    if ((hinfo.Page != null))
    {
        hoverTab = hinfo.Page;
        //Make sure there is a TabPage being dragged.
        if (e.Data.GetDataPresent(typeof(XtraTabPage)))
        {
            e.Effect = DragDropEffects.Move;
            dragTab = (XtraTabPage)e.Data.GetData(typeof(XtraTabPage));
            // can't use the TabIndex on the control because it changes
            // when we move the tab page.
            itemDragIndex = FindIndex(dragTab);
            dropLocationIndex = FindIndex(hoverTab);
            //Don't do anything if we are hovering over ourself.
            if (itemDragIndex != dropLocationIndex)
            {
                selTab = xtcMain.TabPages[itemDragIndex];
                repTab = xtcMain.TabPages[dropLocationIndex];
                //
                xtcMain.TabPages.Move(dropLocationIndex, selTab);
                xtcMain.TabPages.Move(itemDragIndex, repTab);
                xtcMain.SelectedTabPage = selTab;
            }
        }
    }
    else
    {
        e.Effect = DragDropEffects.None;
    }

在 MouseDown 事件中的code：

    CalcRectDragBox(e.X, e.Y);


    // Handle Mouse move only if left button is pressed.
    if (e.Button == MouseButtons.Left)
    {
        // If the mouse moves outside the rectangle, start the drag.
        if (!rectDragBoxFromMouseDown.Equals(Rectangle.Empty) & !rectDragBoxFromMouseDown.Contains(e.X, e.Y))
        {
            isDragging = true;
            dragOffset = new Point(e.X, e.Y);
            Invalidate();
            // Proceed with the drag and drop.
            DragDropEffects dropEffect = DoDragDrop(xtcMain.SelectedTabPage, DragDropEffects.Move);
            // Reset the drag box to avoid reentry of drag.
            CalcRectDragBox(e.X, e.Y);
            isDragging = false;
            dragOffset = Point.Empty;
            Invalidate();
        }
    }

如果你有不同大小的标签，张贴的代码将导致快如闪电的标签之间切换，如果您对重叠的区域的大小不同悬停。 为了防止这种情况，我只是说在dragOver处理一个简单的标志，忽略未来DragOver事件。 在上面的DragOver里面相应的 位置加入这个标志ignoreNextDrag，具体代码如下：

    if (itemDragIndex != dropLocationIndex && !ignoreNextDrag)
    {
        ignoreNextDrag = true;
        selTab = tabControlClientModules.TabPages[itemDragIndex];
        repTab = tabControlClientModules.TabPages[dropLocationIndex];
        //
        tabControlClientModules.TabPages.Move(dropLocationIndex, selTab);
        tabControlClientModules.TabPages.Move(itemDragIndex, repTab);
        tabControlClientModules.SelectedTabPage = selTab;
    }
    else
    {
        ignoreNextDrag = false;

    }