在没有轮询的情况下使用C#检测活动窗口已更改

Question

当当前活动窗口发生变化时,如何调用回调.我已经看到了如何使用CBTProc完成它.但是,全局事件不容易与托管代码挂钩.我有兴趣找到一种不需要轮询的方法.我更喜欢事件驱动的方法.

问候

Answer 1

创建一个新的Windows窗体项目,添加一个文本框,使其成为多行,并将文本框Dock属性设置为填充,命名为Log并粘贴以下代码(您需要将System.Runtime.InteropServices添加到您的使用中). ..

    WinEventDelegate dele = null;

    public Form1()
    {
        InitializeComponent();
        dele = new WinEventDelegate(WinEventProc);
        IntPtr m_hhook = SetWinEventHook(EVENT_SYSTEM_FOREGROUND, EVENT_SYSTEM_FOREGROUND, IntPtr.Zero, dele, 0, 0, WINEVENT_OUTOFCONTEXT);
    }

    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);

    private const uint WINEVENT_OUTOFCONTEXT = 0;
    private const uint EVENT_SYSTEM_FOREGROUND = 3;

    [DllImport("user32.dll")]
    static extern IntPtr GetForegroundWindow();

    [DllImport("user32.dll")]
    static extern int GetWindowText(IntPtr hWnd, StringBuilder text, int count);

    private string GetActiveWindowTitle()
    {
        const int nChars = 256;
        IntPtr handle = IntPtr.Zero;
        StringBuilder Buff = new StringBuilder(nChars);
        handle = GetForegroundWindow();

        if (GetWindowText(handle, Buff, nChars) > 0)
        {
            return Buff.ToString();
        }
        return null;
    }

    public void WinEventProc(IntPtr hWinEventHook, uint eventType, IntPtr hwnd, int idObject, int idChild, uint dwEventThread, uint dwmsEventTime)
    {
        Log.Text += GetActiveWindowTitle() + "\r\n";
    } 

Answer 2

我知道这个线程已经老了,但是为了将来使用:运行代码时,你会发现一段时间后崩溃了.这是由Form构造函数中的行引起的:

public Form1()
    {
        InitializeComponent();
        WinEventDelegate dele = new WinEventDelegate(WinEventProc);//<-causing ERROR
        IntPtr m_hhook = SetWinEventHook(EVENT_SYSTEM_FOREGROUND, EVENT_SYSTEM_FOREGROUND, IntPtr.Zero, dele, 0, 0, WINEVENT_OUTOFCONTEXT);
    }

而不是上述内容进行以下修改:

public Form1()
        {
            InitializeComponent();
            dele = new WinEventDelegate(WinEventProc); 
            IntPtr m_hhook = SetWinEventHook(EVENT_SYSTEM_FOREGROUND, EVENT_SYSTEM_FOREGROUND, IntPtr.Zero, dele, 0, 0, WINEVENT_OUTOFCONTEXT);
        }
WinEventDelegate dele = null;

..现在按预期工作!

Answer 3

您可以使用SetWinEventHook和收听EVENT_SYSTEM_FOREGROUND活动.使用该WINEVENT_OUTOFCONTEXT标志可以避免全局挂钩问题.