检测到前景以暂停窗口的请求

Question

Is there a way to detect a request foreground a window in c#? What I'm trying to do is to suspend a process (not the process doing the detecting) when the user switches their focus to another window, and then resume the process when they switch back.

I managed to detect when the user switches their focus away, but since the process is suspended, I don't know how to detect if they try to switch back.

Edit: I wrote process 1 which is the process doing the detecting and suspending

Process 2 is the external process that I'm detecting whether the user has focus on it or not (from process 1). If the user switches their focus from process 2, suspend process 2. And when they switch back, resume it (from process 1). What I don't know is how to detect if the user attwmpts to switches back if process 2 is suspended.

Answer 1

Depending on the monitored application's framework, you may be able to get focus change events for it by using UI Automation, something like (copied from MSDN):

`AutomationFocusChangedEventHandler focusHandler = null;

/// <summary>
/// Create an event handler and register it.
/// </summary>
public void SubscribeToFocusChange()
{
    focusHandler = new AutomationFocusChangedEventHandler(OnFocusChange);
    Automation.AddAutomationFocusChangedEventHandler(focusHandler);
}

/// <summary>
/// Handle the event.
/// </summary>
/// <param name="src">Object that raised the event.</param>
/// <param name="e">Event arguments.</param>
private void OnFocusChange(object src, AutomationFocusChangedEventArgs e)
{
    // TODO Add event handling code.
    // The arguments tell you which elements have lost and received focus.
    System.Windows.Automation.AutomationElement element = src as System.Windows.Automation.AutomationElement;
    if(element.Current.ProcessId == "MontioredApplicationProcessId")
    {
        //Monitored application has focus!
    }
    else
        //Monitored application does not have focus
}

/// <summary>
/// Cancel subscription to the event.
/// </summary>
public void UnsubscribeFocusChange()
{
    if (focusHandler != null)
    {
        Automation.RemoveAutomationFocusChangedEventHandler(focusHandler);
    }
}`