Question

我正在遍历给定Canvas对象的所有子节点。麻烦的是，它只影响了两个孩子中的一个。我在另一个类似事件中的另一次迭代工作得很好。我有这个，所以你可以拖动元素：

    private Point lastmousepoint;   
    private void Window_MouseMove(object sender, MouseEventArgs e)
    {
        if (e.LeftButton == System.Windows.Input.MouseButtonState.Pressed)
        {                
            Point mousepos = e.GetPosition(this);
            foreach (UIElement element in canvas1.Children)
            {
                Canvas.SetLeft(element, Canvas.GetLeft(element) + (mousepos.X - lastmousepoint.X));
                Canvas.SetTop(element, Canvas.GetTop(element) + (mousepos.Y - lastmousepoint.Y));
                lastmousepoint = mousepos;
            }
        }
        e.Handled = true;
    }
    private void Window_MouseLeftButtonDown(object sender, MouseButtonEventArgs e)
    {
        lastmousepoint = e.GetPosition(this);
        e.Handled = true;
    }
    private void Window_MouseLeftButtonUp(object sender, MouseButtonEventArgs e)
    {
        e.Handled = true;
    }

但是这两个文本中只有一个是移动的，而它们都应该移动。实际运动很好并按预期工作。

此代码

    private int CurrentScaleLevel = 0;
    private void Window_MouseWheel(object sender, MouseWheelEventArgs e)
    {
        foreach (UIElement element in canvas1.Children)
        {
            Point p = e.MouseDevice.GetPosition(element);
            Matrix m = element.RenderTransform.Value;
            if (e.Delta > 0)
            {
                CurrentScaleLevel++;
                m.ScaleAtPrepend(1.1, 1.1, p.X, p.Y);
            }
            else
            {
                CurrentScaleLevel--;
                m.ScaleAtPrepend(1 / 1.1, 1 / 1.1, p.X, p.Y);
            }
            Canvas.SetLeft(element, Canvas.GetLeft(element) + m.OffsetX);
            Canvas.SetTop(element, Canvas.GetTop(element) + m.OffsetY);
            m.Translate(-m.OffsetX, -m.OffsetY);
            element.RenderTransform = new MatrixTransform(m);
        }
        e.Handled = true;
    }

影响两个对象就好了，就像它应该的那样。

Answer 1

你可能不想要

lastmousepoint = mousepos;

在foreach循环中，因为在后续迭代(mousepos.X - lastmousepoint.X)将始终为零，(mousepos.Y - lastmousepoint.Y)也是如此。添加0当然意味着没有动作。

Canvas.Children的迭代问题

1 个答案: