IsMouseCaptured变为False

Question

我正在实施一个简单的Drag'n'Drop Bahevior。 首先，我订阅鼠标事件：

    protected override void OnAttached()
    {
        base.OnAttached();
        base.AssociatedObject.PreviewMouseLeftButtonDown += this.AssociatedObject_PreviewMouseLeftButtonDown;
        base.AssociatedObject.PreviewMouseLeftButtonUp += this.AssociatedObject_PreviewMouseLeftButtonUp;
        base.AssociatedObject.PreviewMouseMove += this.AssociatedObject_PreviewMouseMove;
    }

然后我抓住了鼠标：

    private void AssociatedObject_PreviewMouseLeftButtonDown(object sender, MouseButtonEventArgs e)
    {
        this.startPoint = e.GetPosition(base.AssociatedObject);
        base.AssociatedObject.CaptureMouse();
    }

处理鼠标移动：

private void AssociatedObject_PreviewMouseMove(object sender, MouseEventArgs e)
{
    if (base.AssociatedObject.IsMouseCaptured)
    {
       ...
    }
}

在按下鼠标按钮后立即输入此方法时，IsMouseCaptured为true。但是在IsMouseCaptured之后输入它总是假的。我做错了什么？

提前致谢！

Answer 1

感谢Hans Passant，我已经像这样更新了代码：

    /// <summary>
    /// Handles pressing Mouse Button over the Control.
    /// </summary>
    private void AssociatedObject_PreviewMouseLeftButtonDown(object sender, MouseButtonEventArgs e)
    {
        this.startPoint = e.GetPosition(base.AssociatedObject);
        base.AssociatedObject.CaptureMouse();
        e.Handled = true;
    }

将事件标记为已处理有助于在拖动时捕获鼠标。