c# - 我怎么知道在发送打印命令(按下 "Ctrl+P"按钮)后我应该等待 PrintDialog 多长时间？

Question

我正在使用 C# 编写一个控制台应用程序，我在其中通过代码触发打印作业。我的问题是我不知道在发送命令到 Print 后我应该等待 Print Dialog 多长时间。目前我使用的线程 sleep 时间为 1000 毫秒。

//Sending Commands to Print(to press "Ctrl+P" button).
 SendKeys.SendWait("^(p)");

 Thread.Sleep(1000);

 //Sending Commands to Print(to press "Enter" Button).
 SendKeys.SendWait("{ENTER}");

谁能帮我解决这个问题。任何帮助将不胜感激。

提前致谢

更新:

这是我的全部代码:

//Launch the file from the location specified in.
White.Core.Application application =White.Core.Application.Launch(@path);

Console.WriteLine("launch is done");

Thread.Sleep(_delayOfPrint);

//Sending Commands to Print(to press "Ctrl+P" button).
SendKeys.SendWait("^(p)");

Thread.Sleep(1000);

//Sending Commands to Print(to press "Enter" Button).
SendKeys.SendWait("{ENTER}");

//Get the current time as the document fired for print job.
_printedTime = DateTime.Now;

Thread.Sleep(1500);

//Closing the window.
SendKeys.SendWait("%{F4}");

Answer 1

我最多等待几秒钟，但在这段时间内我会定期使用 Win32 函数 FindWindowEx 来查看打印对话框是否真的出现，如果出现则继续。您可以使用如下代码获取进程的主窗口:

Process[] processes = Process.GetProcessesByName(appName);
foreach (Process p in processes)
{
     IntPtr pFoundWindow = p.MainWindowHandle;
}

然后您可以将找到的主窗口句柄传递给 FindWindowEx 以细读子窗口以检查打印对话框。 FindWindowEx 具有如下 PInvoke 签名:

[DllImport("user32.dll", SetLastError = true)]
static extern IntPtr FindWindowEx(IntPtr hwndParent, IntPtr hwndChildAfter, string lpszClass, string lpszWindow);

[DllImport("user32.dll", SetLastError = true)]
public static extern IntPtr FindWindowEx(IntPtr parentHandle, IntPtr childAfter, string className,  IntPtr windowTitle);

编辑 2: 由于 OP 似乎要求我提供一个完美的工作函数，我写了一个通用的函数来完成这个技巧并对其进行了测试。在这里，工作通用代码等待任何子窗口。在这种情况下调用 WaitForChildWindow("myApp", "Print", 5000):

/// <summary>
/// Wait for a child window of an application to appear
/// </summary>
/// <param name="appName">Application name to check (will check all instances)</param>
/// <param name="childWindowName">Name of child window to look for (titlebar)</param>
/// <param name="timeout">Maximum time, in milliseconds, to wait</param>
/// <returns>True if the window was found; false if it wasn't.</returns>
public static bool WaitForChildWindow(string appName, string childWindowName, int timeout)
{
    int sleepTime = timeout;
    while (sleepTime > 0)
    {
        Process[] processes = Process.GetProcessesByName(appName);
        foreach (Process p in processes)
        {
            IntPtr pMainWindow = p.MainWindowHandle;
            IntPtr pFoundWindow = FindWindowEx(pMainWindow, IntPtr.Zero, null, childWindowName);
            if (pFoundWindow != IntPtr.Zero)
                return true;
        }
        Thread.Sleep(100);
        sleepTime -= 100;
    }

    // Timed out!
    return false;
}

编辑 3:这是为没有子关系的仅拥有的窗口执行此操作的另一种方法:

[DllImport("user32.dll", SetLastError = true)]
static extern uint GetWindowThreadProcessId(IntPtr hwnd, IntPtr processId);
[DllImport("user32.dll")]
[return: MarshalAs(UnmanagedType.Bool)]
static extern bool EnumThreadWindows(uint dwThreadId, EnumThreadDelegate lpfn, IntPtr lParam);
[DllImport("user32", SetLastError = true, CharSet = CharSet.Auto)]
private extern static int GetWindowText(IntPtr hWnd, StringBuilder text, int maxCount);

public delegate bool EnumThreadDelegate(IntPtr hwnd, IntPtr lParam);

static bool EnumThreadCallback(IntPtr hWnd, IntPtr lParam)
{
    StringBuilder text = new StringBuilder(500);
    GetWindowText(hWnd, text, 500);
    if (text.ToString() == "Print")
        return false;
    return true;
}

public static bool FindThreadPrintWindow(uint threadId)
{
    return !EnumThreadWindows(threadId, EnumThreadCallback, IntPtr.Zero);
}

public static bool WaitForOwnedPrintWindow(string appName, int timeout)
{
    int sleepTime = timeout;
    while (sleepTime > 0)
    {
        Process[] processes = Process.GetProcessesByName(appName);
        foreach (Process p in processes)
        {
            IntPtr pMainWindow = p.MainWindowHandle;
            uint threadId = GetWindowThreadProcessId(pMainWindow, IntPtr.Zero);
            if (FindThreadPrintWindow(threadId))
                return true;
        }
        Thread.Sleep(100);
        sleepTime -= 100;
    }

    // Timed out!
    return false;
}