通过SendMessage或其他东西异步GetForegroundWindow？

Question

有没有办法通知焦点何时从任何窗口更改到另一个窗口(甚至在Windows应用程序之间),以便我可以在用户更改焦点时立即调用我的委托？

我一直在想我可能只需要进行民意调查:( :(每1秒钟调用GetForegroundWindow但我真的不想那样做).

Answer 1

SetWinEventHook()可能是你最好的选择; 您可以收听EVENT_SYSTEM_FOREGROUND以侦听前景窗口更改 - 甚至可以收听EVENT_OBJECT_FOCUS以在应用程序内和控件内侦听更细粒度的焦点更改.

您需要将其与WINEVENT_OUTOFCONTEXT标志一起使用; 这意味着更改通知将异步传递到您自己的应用程序,因此您不需要单独的DLL - 您仍然需要P/Invoke.但通知不会是即时的 - 可能会有一个小的延迟 - 但这是异步的暗示.如果你想在没有任何延迟的情况下立即做一些事情,你将需要使用C++和进程内挂钩(带有WINEVENT_INCONTEXT的SetWinEventHook或者SetSetWindowsHookEx样式的钩子.)

这是一个似乎正在寻找你想要的样本:

using System;
using System.Windows;
using System.Windows.Forms;
using System.Runtime.InteropServices;

class ForegroundTracker
{
            // Delegate and imports from pinvoke.net:

    delegate void WinEventDelegate(IntPtr hWinEventHook, uint eventType,
        IntPtr hwnd, int idObject, int idChild, uint dwEventThread, uint dwmsEventTime);

    [DllImport("user32.dll")]
    static extern IntPtr SetWinEventHook(uint eventMin, uint eventMax, IntPtr
       hmodWinEventProc, WinEventDelegate lpfnWinEventProc, uint idProcess,
       uint idThread, uint dwFlags);

    [DllImport("user32.dll")]
    static extern bool UnhookWinEvent(IntPtr hWinEventHook);

            // Constants from winuser.h
    const uint EVENT_SYSTEM_FOREGROUND = 3;
    const uint WINEVENT_OUTOFCONTEXT = 0;

    // Need to ensure delegate is not collected while we're using it,
    // storing it in a class field is simplest way to do this.
    static WinEventDelegate procDelegate = new WinEventDelegate(WinEventProc);

    public static void Main()
    {
        // Listen for foreground changes across all processes/threads on current desktop...
        IntPtr hhook = SetWinEventHook(EVENT_SYSTEM_FOREGROUND, EVENT_SYSTEM_FOREGROUND, IntPtr.Zero,
                procDelegate, 0, 0, WINEVENT_OUTOFCONTEXT);

        // MessageBox provides the necessary mesage loop that SetWinEventHook requires.
        MessageBox.Show("Tracking focus, close message box to exit.");

        UnhookWinEvent(hhook);
    }

    static void WinEventProc(IntPtr hWinEventHook, uint eventType,
        IntPtr hwnd, int idObject, int idChild, uint dwEventThread, uint dwmsEventTime)
    {
        Console.WriteLine("Foreground changed to {0:x8}", hwnd.ToInt32()); 
    }
}

Answer 2

上面的例子就像一个冠军.我重构了一点,以创建一个可能有用的类.我没有定义所有常量,所以如果你想捕获其他事件,你需要添加一些常量.

using System;
using System.Runtime.InteropServices;

#pragma warning disable 1591
// ReSharper disable InconsistentNaming

namespace MosaiqPerformanceMonitor {
     public class EventHook {
          public delegate void WinEventDelegate(
                IntPtr hWinEventHook, uint eventType,
                IntPtr hWnd, int idObject, int idChild, uint dwEventThread, uint dwmsEventTime);

          [DllImport("user32.dll")]
          public static extern IntPtr SetWinEventHook(
                uint eventMin, uint eventMax, IntPtr hmodWinEventProc, WinEventDelegate lpfnWinEventProc,
                uint idProcess, uint idThread, uint dwFlags);

          [DllImport("user32.dll")]
          public static extern bool UnhookWinEvent(IntPtr hWinEventHook);

          public const uint EVENT_SYSTEM_FOREGROUND = 3;
          public const uint WINEVENT_OUTOFCONTEXT = 0;
          public const uint EVENT_OBJECT_CREATE = 0x8000;

          readonly WinEventDelegate _procDelegate;
          readonly IntPtr _hWinEventHook;

          public EventHook(WinEventDelegate handler, uint eventMin, uint eventMax) {
                _procDelegate = handler;
                _hWinEventHook = SetWinEventHook(eventMin, eventMax, IntPtr.Zero, handler, 0, 0, WINEVENT_OUTOFCONTEXT);
          }

          public EventHook(WinEventDelegate handler, uint eventMin)
                : this(handler, eventMin, eventMin) {
          }

          public void Stop() {
                UnhookWinEvent(_hWinEventHook);
          }

          // Usage Example for EVENT_OBJECT_CREATE (http://msdn.microsoft.com/en-us/library/windows/desktop/dd318066%28v=vs.85%29.aspx)
          // var _objectCreateHook = new EventHook(OnObjectCreate, EventHook.EVENT_OBJECT_CREATE);
          // ...
          // static void OnObjectCreate(IntPtr hWinEventHook, uint eventType, IntPtr hWnd, int idObject, int idChild, uint dwEventThread, uint dwmsEventTime) {
          //    if (!Win32.GetClassName(hWnd).StartsWith("ClassICareAbout"))
          //        return;
          // Note - in Console program, doesn't fire if you have a Console.ReadLine active, so use a Form
     }
}