GetActiveWindow返回0

Question

        IntPtr win = GetActiveWindow();
        RECT dimensions;
        GetWindowRect(win, out dimensions);

上面的代码似乎返回一个矩形，其尺寸为0。右和尺寸。左边的值。我对winapi的提及如下。

    [DllImport("user32.dll", SetLastError=true)]
    static extern IntPtr GetActiveWindow();

    [DllImport("user32.dll", SetLastError = true)]
    static extern IntPtr GetWindow(IntPtr hWnd, uint uCmd);

    enum GetWindow_Cmd : uint
    {
        GW_HWNDFIRST = 0,
        GW_HWNDLAST = 1,
        GW_HWNDNEXT = 2,
        GW_HWNDPREV = 3,
        GW_OWNER = 4,
        GW_CHILD = 5,
        GW_ENABLEDPOPUP = 6
    }
    [DllImport("user32.dll", SetLastError=true))]
    [return: MarshalAs(UnmanagedType.Bool)]
    static extern bool GetWindowRect(IntPtr hWnd, out RECT lpRect);

    [StructLayout(LayoutKind.Sequential)]
    public struct RECT
    {
        public int Left;        // x position of upper-left corner  
        public int Top;         // y position of upper-left corner  
        public int Right;       // x position of lower-right corner  
        public int Bottom;      // y position of lower-right corner  
    }

GetActiveWindow似乎没有返回用户当前选择的窗口。我注意到，如果我将以上内容更改为以下内容似乎可以正常工作。

        IntPtr win = GetForegroundWindow();
        RECT dimensions;
        GetWindowRect(win, out dimensions);

编辑：带支票的代码。

IntPtr win = GetActiveWindow();
if (win == IntPtr.Zero)
{
    //this triggers
    Debug.WriteLine("Win: " + win.ToString());
    Debug.WriteLine("Unable to get window handle.");
}
else
{
    RECT dimensions;
    uint pid;
    GetWindowThreadProcessId(win, out pid);
    Debug.WriteLine(Marshal.GetLastWin32Error().ToString());
    Debug.WriteLine(pid.ToString());
    if (GetWindowRect(win, out dimensions))
    {
        Debug.WriteLine(dimensions.Top.ToString() + ", " + dimensions.Right.ToString() + ", "
            + dimensions.Bottom.ToString() + ", " + dimensions.Left.ToString() + "\nPID: " + pid.ToString());
        ScreenCapture sc = new ScreenCapture();
        int width = dimensions.Right - dimensions.Left;
        int height = dimensions.Bottom - dimensions.Top;
        Clipboard.SetImage(sc.CaptureArea(dimensions.Left, dimensions.Top, width, height));
    }
    else
    {
        Debug.WriteLine(Marshal.GetLastWin32Error().ToString() + "\nPID:" + pid.ToString());
        Debug.WriteLine("Unable to get window dimensions.\nPID:" + pid.ToString());
    }
}

SSCCE：

using System;
using System.Runtime.InteropServices;

namespace GetWindow
{
    class Program
    {
        [DllImport("user32.dll", SetLastError = true)]
        static extern IntPtr GetActiveWindow();

        static void Main(string[] args)
        {
            IntPtr win = GetActiveWindow();
            Console.WriteLine("Win: " + win.ToString()); //outputs 0 to console
            Console.Read();
        }
    }
}

Answer 1

这很正常。 GetActiveWindow获取调用线程的活动窗口。如果调用线程不拥有前台窗口，则GetActiveWindow将返回NULL。