表单在后台（不是焦点）时不会刷新Picturebox

Question

目的：通过从此窗口捕获图像并使用计时器在图片框中显示图像来镜像外部过程的窗口。

问题：当我的应用程序处于焦点时，一切都很好！但是如果我将焦点切换到另一个窗口（而不是我的应用程序），则图片框会停止刷新图像。当我再次专注于我的应用程序时，一切都恢复正常。

限制：即使我的应用程序在后台，我也需要图片框继续更新。

定时器捕获图像并显示在图片框中：

private void timer_picBOX_refresh_Tick(object sender, EventArgs e)
    {
        pictureBox1.BackgroundImage = PrintScreen.CaptureWindow(GAME_MainHandle);            
        pictureBox1.Refresh();            
    }

捕获特定窗口的类：

public class class_ScreenCapture
{
    public Image CaptureScreen()
    {
        return CaptureWindow(User32.GetDesktopWindow());
    }

    /// <summary>
    /// Creates an Image object containing a screen shot of a specific window
    /// </summary>
    public Image CaptureWindow(IntPtr handle, int imgX = 0, int imgY = 0, int largura = 0, int altura = 0)
    {
        // get te hDC of the target window
        IntPtr hdcSrc = User32.GetWindowDC(handle);
        // get the size
        User32.RECT windowRect = new User32.RECT();
        User32.GetWindowRect(handle, ref windowRect);

        if (largura == 0 || altura == 0)
        {
            largura = windowRect.right - windowRect.left;
            altura = windowRect.bottom - windowRect.top;
        }

        // create a device context we can copy to
        IntPtr hdcDest = GDI32.CreateCompatibleDC(hdcSrc);
        // create a bitmap we can copy it to,
        // using GetDeviceCaps to get the width/height
        IntPtr hBitmap = GDI32.CreateCompatibleBitmap(hdcSrc, largura, altura);
        // select the bitmap object
        IntPtr hOld = GDI32.SelectObject(hdcDest, hBitmap);
        // bitblt over
        GDI32.BitBlt(hdcDest, 0, 0, largura, altura, hdcSrc, imgX, imgY, GDI32.SRCCOPY);
        // restore selection
        GDI32.SelectObject(hdcDest, hOld);
        // clean up 
        GDI32.DeleteDC(hdcDest);
        User32.ReleaseDC(handle, hdcSrc);

        // get a .NET image object for it
        Image img = Image.FromHbitmap(hBitmap);
        // free up the Bitmap object
        GDI32.DeleteObject(hBitmap);

        return img;
    }        

    /// <summary>
    /// Helper class containing Gdi32 API functions
    /// </summary>
    private class GDI32
    {

        public const int SRCCOPY = 0x00CC0020; // BitBlt dwRop parameter

        [DllImport("gdi32.dll")]
        public static extern bool BitBlt(IntPtr hObject, int nXDest, int nYDest,
            int nWidth, int nHeight, IntPtr hObjectSource,
            int nXSrc, int nYSrc, int dwRop);
        [DllImport("gdi32.dll")]
        public static extern IntPtr CreateCompatibleBitmap(IntPtr hDC, int nWidth,
            int nHeight);
        [DllImport("gdi32.dll")]
        public static extern IntPtr CreateCompatibleDC(IntPtr hDC);
        [DllImport("gdi32.dll")]
        public static extern bool DeleteDC(IntPtr hDC);
        [DllImport("gdi32.dll")]
        public static extern bool DeleteObject(IntPtr hObject);
        [DllImport("gdi32.dll")]
        public static extern IntPtr SelectObject(IntPtr hDC, IntPtr hObject);
    }

    /// <summary>
    /// Helper class containing User32 API functions
    /// </summary>
    private class User32
    {
        [StructLayout(LayoutKind.Sequential)]
        public struct RECT
        {
            public int left;
            public int top;
            public int right;
            public int bottom;
        }

        [DllImport("user32.dll")]
        public static extern IntPtr GetDesktopWindow();
        [DllImport("user32.dll")]
        public static extern IntPtr GetWindowDC(IntPtr hWnd);
        [DllImport("user32.dll")]
        public static extern IntPtr ReleaseDC(IntPtr hWnd, IntPtr hDC);
        [DllImport("user32.dll")]
        public static extern IntPtr GetWindowRect(IntPtr hWnd, ref RECT rect);

    }
}

Answer 1

测试一下。

private void timer_picBOX_refresh_Tick(object sender, EventArgs e)
{
    pictureBox1.Image = PrintScreen.CaptureWindow(GAME_MainHandle);            
    pictureBox1.Refresh();
    Refresh();
}