Question

我需要能够确定ContainsFocus（特别是Windows窗体）上Control的更改时间。覆盖OnGotFocus不是答案。当我将表单带到前台时，ContainsFocus为真，Focused为假。那么OnGotFocus是否有ContainsFocus等价物？或者其他任何方式？

Answer 1

注意：如果您有子控件，则会触发子控件的GotFocus事件。否则调用表单的OnGotFocus。

如果我正确理解了这个问题，那么这应该有效：

    bool lastNotificationWasGotFocus = false;

    protected override void OnControlAdded(ControlEventArgs e)
    {
        SubscribeEvents(e.Control);
        base.OnControlAdded(e);
    }

    protected override void OnControlRemoved(ControlEventArgs e)
    {
        UnsubscribeEvents(e.Control);
        base.OnControlRemoved(e);
    }

    private void SubscribeEvents(Control control)
    {
        control.GotFocus += new EventHandler(control_GotFocus);
        control.LostFocus += new EventHandler(control_LostFocus);
        control.ControlAdded += new ControlEventHandler(control_ControlAdded);
        control.ControlRemoved += new ControlEventHandler(control_ControlRemoved);

        foreach (Control innerControl in control.Controls)
        {
            SubscribeEvents(innerControl);
        }
    }

    private void UnsubscribeEvents(Control control)
    {
        control.GotFocus -= new EventHandler(control_GotFocus);
        control.LostFocus -= new EventHandler(control_LostFocus);
        control.ControlAdded -= new ControlEventHandler(control_ControlAdded);
        control.ControlRemoved -= new ControlEventHandler(control_ControlRemoved);

        foreach (Control innerControl in control.Controls)
        {
            UnsubscribeEvents(innerControl);
        }
    }

    private void control_ControlAdded(object sender, ControlEventArgs e)
    {
        SubscribeEvents(e.Control);
    }

    private void control_ControlRemoved(object sender, ControlEventArgs e)
    {
        UnsubscribeEvents(e.Control);
    }

    protected override void OnGotFocus(EventArgs e)
    {
        CheckContainsFocus();
        base.OnGotFocus(e);
    }

    protected override void OnLostFocus(EventArgs e)
    {
        CheckLostFocus();
        base.OnLostFocus(e);
    }

    private void control_GotFocus(object sender, EventArgs e)
    {
        CheckContainsFocus();
    }

    private void control_LostFocus(object sender, EventArgs e)
    {
        CheckLostFocus();
    }

    private void CheckContainsFocus()
    {
        if (lastNotificationWasGotFocus == false)
        {
            lastNotificationWasGotFocus = true;
            OnContainsFocus();
        }
    }

    private void CheckLostFocus()
    {
        if (ContainsFocus == false)
        {
            lastNotificationWasGotFocus = false;
            OnLostFocus();
        }
    }

    private void OnContainsFocus()
    {
        Console.WriteLine("I have the power of focus!");
    }

    private void OnLostFocus()
    {
        Console.WriteLine("I lost my power...");
    }

Answer 2

解决此问题的一种方法是使用Timer。这绝对是蛮力，但它完成了工作：

private Timer m_checkContainsFocusTimer = new Timer();
private bool m_containsFocus = true;

m_checkContainsFocusTimer.Interval = 1000; // every second is good enough
m_checkContainsFocusTimer.Tick += new EventHandler(CheckContainsFocusTimer_Tick);
m_checkContainsFocusTimer.Start();

private void CheckContainsFocusTimer_Tick(object sender, EventArgs e)
{
    if (!m_containsFocus && ContainsFocus)
        OnAppGotFocus();

    m_containsFocus = ContainsFocus;
}

但有更简单的方法吗？

Answer 3

处理GotFocus和LostFocus事件应该这样做。

需要注意的另一件事...... SDK说明了ContainsFocus属性：

您可以使用此属性来确定无论是控制还是任何控制其中包含的控件有输入焦点。判断是否无论如何，控制都有焦点是否有任何子控件焦点，使用聚焦属性。

编辑：

处理GotFocus事件时，您可能仍需要检查Focused / ContainsFocus属性，具体取决于控件层次结构的设置方式。

如果控件或其任何子项具有焦点，则ContainsFocus将为true。只有当具体控制本身具有焦点时，焦点才会成立，无论其子女如何。

ContainsFocus更改时有没有办法捕获？

3 个答案: