拦截和取消WinForms按钮的Click事件

Question

有没有一种方法可以从父控件中捕获Button的Click事件，并防止在父控件中的变量为true时发生该事件？

例如：

private void AssignEventOverrides()
{
    foreach (Button button in Buttons) 
    {
        // Get the event assigned at design time
        var someUnknownEventHandler = GetTheClickHandlerSomehow(button);

        // Unsubscribe the unknown event
        button.Click -= SomeUnknownEventHandler;

        // Assign the intercepting event
        button.Click += button_Click;
    }
}

private void button_Click(object sender, EventArgs e)
{
    if (!preventClick)
    {
        // Fire the intercepted event that was previously unsubscribed
    }
}

希望有比上述示例更好的方法来执行此操作。 只是要注意，我对分配给上述按钮的事件没有任何控制权。 它们已在其他位置订阅，并且如果使用方父控件上的变量为true，则只需阻止它们发生。

我的真实情况是：

我正在使用Windows Mobile 6.5（旧版应用程序重写），我创建了一个面板控件，其中可以包含N个子控件。 面板控件允许iPhone样式的垂直滚动。 我订阅了子Control的MouseMove事件，并将变量_isScrolling设置为true 。 在MouseUp事件中，我将_isScrolling设置为false 。

由于Click在MouseUp之前发生，因此我可以在Click事件中进行检查，以确保在按下按钮时没有发生滚动。 因此，基本上，如果发生面板滚动，则需要防止触发Click事件（在设计时订阅）。

Answer 1

这可能会提供一些有用的见解

如何从控件中删除所有事件处理程序

具体来说，看看

private void RemoveClickEvent(Button b)
{
    FieldInfo f1 = typeof(Control).GetField("EventClick", 
        BindingFlags.Static | BindingFlags.NonPublic);
    object obj = f1.GetValue(b);
    PropertyInfo pi = b.GetType().GetProperty("Events",  
        BindingFlags.NonPublic | BindingFlags.Instance);
    EventHandlerList list = (EventHandlerList)pi.GetValue(b, null);
    list.RemoveHandler(obj, list[obj]);
}

Answer 2

作为解决问题的另一种方法，为什么不只是对托管表单进行子类化并寻找目标的点击。 如果您的preventClick为true，则将消息标记为已处理，以防止其传递给孩子。

Answer 3

禁用按钮而不是将父控件中的变量设置为true怎么办？

更新：设置button.Enabled = false肯定会阻止Click事件引发:)

更新2（针对真实场景）：考虑创建自定义按钮

public class ScrollableButton : Button
{
    private bool _isScrolling;

    protected override void OnMouseMove(MouseEventArgs mevent)
    {
        _isScrolling = true;
        base.OnMouseMove(mevent);
    }

    protected override void OnMouseUp(MouseEventArgs mevent)
    {
        base.OnMouseUp(mevent);
        _isScrolling = false;
    }

    public bool IsScrolling { get; set; }

    protected override void OnClick(EventArgs e)
    {
        if (!_isScrolling)
            base.OnClick(e);
    }
}

只需将默认按钮替换为可滚动按钮即可。

Answer 4

感谢Hehewaffles的回答 ，这是我想出的解决方案：

/// <summary>
/// Dictionary for holding the controls design time Click EventHandlers.
/// </summary>
private Dictionary<Control, EventHandler> _interceptedClickEventHandlers;

/// <summary>
/// Recursively moves through the child controls assigning events for scrolling and replacing Click events 
/// with an interception EventHandler that prevents the Click event occuring if the Panel was scrolled.
/// </summary>
/// <param name="control">The control to handle the events for and whose children to recurse through.</param>
private void RecursivelySubscribeChildEvents(Control control)
{
    if (!(control is IPanelItem))
    {
        return;
    }

    // Subscribe the events for the scroll handling
    control.MouseDown += new MouseEventHandler(UIPanel_MouseDown);
    control.MouseMove += new MouseEventHandler(UIPanel_MouseMove);
    control.MouseUp += new MouseEventHandler(UIPanel_MouseUp);

    // Intercept the click event
    FieldInfo eventClickField = typeof(Control).GetField("Click", BindingFlags.NonPublic | BindingFlags.Instance);
    if (eventClickField != null)
    {
        if (_interceptedClickEventHandlers == null)
        {
            _interceptedClickEventHandlers = new Dictionary<Control, EventHandler>();
        }

        // Get the original event and store it against the control for actioning later
        EventHandler eventClick = (EventHandler)eventClickField.GetValue(control);
        _interceptedClickEventHandlers.Add(control, eventClick);

        // Unsubscribe the old event and assign the interception event
        control.Click -= (EventHandler)eventClick;
        control.Click += new EventHandler(UIPanel_ChildClick);
    }

    // Recurse the event subscription operation
    foreach (Control child in control.Controls)
    {
        RecursivelySubscribeChildEvents(child);
    }
}

private void UIPanel_ChildClick(object sender, EventArgs e)
{
    EventHandler interceptedHandler = _interceptedClickEventHandlers[(Control)sender];
    if (interceptedHandler != null)
    {
        // Fire the originally subscribed event if the panel is not scrolling
        if (!_isScrolling)
        {
            interceptedHandler(sender, e);
        }
    }
}