Question

我想模拟WPF中的拖放事件为此，我需要访问存储在“拖放缓冲区”中的数据，并且还需要创建DragEventArgs。我注意到DragEventArgs是密封的，没有公开的ctor。

所以我的问题是：
1.如何创建DragEventArgs的实例？
2.如何访问拖放缓冲区？

Answer 1

我最近这样做了！我使用MouseDown，MouseMove和MouseUp事件模拟拖放。例如，对于我的应用程序，我有一些画布，我想拖放它们。每个画布都有一个id。在MouseDown事件中，我缓冲其id并在MouseMove和MouseUp事件中使用它。 Desktop_Canvas是我的主要画布，包含一些画布。这些画布在我的词典中（dic）。

这是我的代码：

private Dictionary<int, Win> dic = new Dictionary<int, Win>();
    private Point downPoint_Drag = new Point(-1, -1);
    private int id_Drag = -1;
    private bool flag_Drag = false;

    public class Win
    {
        public Canvas canvas = new Canvas();
        public Point downpoint = new Point();

        public Win()
        {
            canvas.Background = new SolidColorBrush(Colors.Gray);
        }
    }

    private void Desktop_Canvas_MouseMove(object sender, MouseEventArgs e)
    {
        try
        {
            Point movePoint = e.GetPosition(Desktop_Canvas);

                    if (flag_Drag && downPoint_Drag != new Point(-1, -1))
                    {
                        double dy1 = movePoint.Y - downPoint_Drag.Y, x = -1, dx1 = movePoint.X - downPoint_Drag.X, y = -1;
                        downPoint_Drag = movePoint;
                        if (x == -1)
                            x = Canvas.GetLeft(dic[id_Drag].canvas) + dx1;
                        if (y == -1)
                            y = Canvas.GetTop(dic[id_Drag].canvas) + dy1;
                        Canvas.SetLeft(dic[id_Drag].canvas, x);
                        Canvas.SetTop(dic[id_Drag].canvas, y);
                    }
        }
        catch
        {
            MouseEventArgs ee = new MouseEventArgs((MouseDevice)e.Device, 10);
            Desktop_Canvas_MouseLeave(null, ee);
        }
    }

    private void Desktop_Canvas_MouseLeftButtonUp(object sender, MouseButtonEventArgs e)
    {
        try
        {
  downPoint_Drag  = new Point(-1, -1);
            id_Drag =-1;
            flag_Drag = false;
        }
        catch
        {
            MouseEventArgs ee = new MouseEventArgs((MouseDevice)e.Device, 10);
            Desktop_Canvas_MouseLeave(null, ee);
        }
    }

    private void Desktop_Canvas_MouseLeave(object sender, MouseEventArgs e)
    {
        MouseButtonEventArgs ee = new MouseButtonEventArgs((MouseDevice)e.Device, 10, MouseButton.Left);
            Desktop_Canvas_MouseLeftButtonUp(null, ee);
    }

    void canvas_MouseLeftButtonDown(object sender, MouseButtonEventArgs e)
    {            
        downPoint_Drag = e.GetPosition(Desktop_Canvas);
        int hoverId = HoverWin(downPoint_Drag);
        flag_Drag = true;
        id_Drag = hoverId;
        dic[id_Drag].downpoint = new Point(downPoint_Drag.X, downPoint_Drag.Y);
    }

    private int HoverWin(Point p)
    {
        foreach (int i in dic.Keys)
        {
                if (dic[i].canvas.IsMouseOver)
                    return i;
        }
        return -1;
    }

在WPF中模拟拖放事件

1 个答案: