.net - 确定停用表单时的激活位置

Question

有谁知道在停用表单时确定哪个窗口将获得焦点的方法？

Answer 1

我找到了答案。不要订阅激活和停用事件，而是在 WndProc 中处理WM_ACTIVATE消息（用于激活和停用）。由于它报告正在激活的窗口句柄，我可以将该句柄与我的表单句柄进行比较，并确定焦点是否正在更改为其中任何一个。

const int WM_ACTIVATE = 0x0006;
const int WA_INACTIVE = 0;
const int WA_ACTIVE = 1;  
const int WA_CLICKACTIVE = 2;  

protected override void WndProc(ref Message m)  
{  
    if (m.Msg == WM_ACTIVATE)  
    {  
         // When m.WParam is WA_INACTIVE, the window is being deactivated and
         // m.LParam is the handle of the window that will be activated.

         // When m.WParam is WA_ACTIVE or WA_CLICKACTIVE, the window is being 
         // activated and m.LParam is the handle of the window that has been 
         // deactivated.
    }  

    base.WndProc(ref m);  
} 

编辑：此方法可以在它适用的窗口之外使用（例如在弹出窗口之外）。

您可以使用 NativeWindow 根据其句柄附加到任何窗口并查看其消息循环。请参见下面的代码示例：

public class Popup : Form
{
    const int WM_ACTIVATE = 0x0006;
    const int WA_INACTIVE = 0;
    private ParentWindowIntercept parentWindowIntercept;

    public Popup(IntPtr hWndParent)
    {
        this.parentWindowIntercept = new ParentWindowIntercept(hWndParent);
    }

    private class ParentWindowIntercept : NativeWindow
    {
        public ParentWindowIntercept(IntPtr hWnd)
        {
            this.AssignHandle(hWnd);
        }

        protected override void WndProc(ref Message m)
        {
            if (m.Msg == WM_ACTIVATE)
            {
                if ((int)m.WParam == WA_INACTIVE)
                {
                    IntPtr windowFocusGoingTo = m.LParam;
                    // Compare handles here
                }
            }

            base.WndProc(ref m);
        } 
    }
}

Answer 2

您应该能够使用Form.ActiveForm静态属性确定活动表单。

Answer 3

在实现自动完成弹出窗口（类似于 VS 中的 Intellisense 窗口）时，我遇到了同样的问题。

该WndProc方法的问题在于，必须将代码添加到发生弹出窗口的任何表单中。

另一种方法是使用计时器并在短暂的间隔后检查 Form.ActiveControl。这样，代码可以更好地封装在编辑器控件或弹出表单中。

Form _txPopup;

// Subscribe whenever convenient
public void IntializeControlWithPopup(Form _hostForm)
{
    _hostForm.Deactivate + OnHostFormDeactivate;
}

Timer _deactivateTimer;
Form _hostForm;
void OnHostFormDeactivate(object sender, EventArgs e)
{
    if (_deactivateTimer == null) 
    {
        _mainForm = sender as Form;
        _deactivateTimer = new Timer();
        _deactivateTimer.Interval = 10;
        _deactivateTimer.Tick += DeactivateTimerTick;
    }
    _deactivateTimer.Start();
}

void  DeactivateTimerTick(object sender, EventArgs e)
{
    _deactivateTimer.Stop();
    Form activeForm = Form.ActiveForm;
    if (_txPopup != null && 
        activeForm != _txPopup && 
        activeForm != _mainForm) 
    { 
        _txPopup.Hide(); 
    }
}