如何檢索在Acrobat中選擇的打印機的名稱？

Question

我想要使用SendMessage Windows API獲取在Acrobat PrintDialog中選擇的打印機的名稱。

這是示例代碼。

static string GetWindowText(hwnd_printDialog_in_Acrobat) 
{ 
    int comboBoxCount = 0; 
    int HWND_PRINTER_NAME = 1 ; 

    List<IntPtr> ChildPtrList = GetChildWindows(hwnd_printDialog_in_Acrobat); 
    for(i=0 ; i < ChildPtrList.Size(); i++) { 
     GetClassName(ChildPtrList[i], sClass, 100); 
     if (sClass.ToString() == "ComboBox") { 
      comboBoxCount++; 
      if (comboBoxCount == HWND_PRINTER_NAME) { 
       hwnd = ChildPtrList[i]; 
       break; 
      } 
     } 
    } 
    ChildPtrList.Clear(); 

    int sSize ; 
    sSize = SendMessageW(hwnd, WM_GETTEXTLENGTH, IntPtr.Zero, IntPtr.Zero)+1; 
    StringBuilder sbTitle = new StringBuilder(sSize); 
    SendMessageW(hwn, WM_GETTEXT, (IntPtr)sSize, sbTitle); 
    return (sbTitle.ToString()); 
} 

sSize的返回值是4; sbTitle.ToString()的值爲「？ - 」等。 預計結果 出了什麼問題？

Answer 1

這裏是我目前的猜測，您的問題：

• HWND_PRINTER_NAME沒有1
• 你正在尋找的類名是不是「組合框」
• 問題在代碼中未列出：
• • 抓取錯誤的父窗口或錯誤地對待句柄
• • SendMessageW的DllImport是錯誤的，或參數處理不當

你確實有上市，使代碼一些錯誤，我的代碼是不完全一樣，但這裏是我的代碼用來試圖找出你的問題。我無法讓它按照你描述的方式行事。我的代碼從來沒有找到一個類名爲「ComboBox」的子窗口。

using System; 
using System.Collections.Generic; 
using System.Runtime.InteropServices; 
using System.Text; 

namespace PrinterChoosenInAcrobat 
{ 
class Program 
{ 
    public const uint WM_GETTEXTLENGTH = 0x000E; 
    private const uint WM_GETTEXT = 0x000D; 

    // External OS calls 
    [DllImport("user32.dll", EntryPoint = "SendMessage", CharSet = CharSet.Auto)] 
    public static extern bool SendMessage(IntPtr hWnd, uint Msg, IntPtr wParam, 
     StringBuilder lParam); 

    [DllImport("user32.dll", SetLastError = true)] 
    public static extern IntPtr SendMessage(IntPtr hWnd, uint Msg, IntPtr wparam, 
     IntPtr lparam); 

    [DllImport("User32.dll")] 
    public static extern Int32 FindWindow(String lpClassName, String lpWindowName); 

    [DllImport("user32.dll")] 
    static extern int GetClassName(IntPtr hWnd, StringBuilder lpClassName, 
    int nMaxCount); 

    static void Main(string[] args) 
    { 
     try 
     { 
      IntPtr windowHandle = (IntPtr)FindWindow("AcrobatSDIWindow", null); 
      string text = GetWindowText(windowHandle); 

      Console.WriteLine(text); 

     } 
     catch (Exception ex) 
     { 
      Console.Out.WriteLine(ex.Message); 
     } 

     // Don't close before I get to read the results 
     Console.WriteLine(); 
     Console.WriteLine("Press Enter to quit."); 
     Console.ReadLine(); 
    } 

    static string GetWindowText(IntPtr hwnd_printDialog_in_Acrobat) 
    { 
     int comboBoxCount = 0; 
     int HWND_PRINTER_NAME = 1; 

     List<IntPtr> ChildPtrList = GetChildWindows(hwnd_printDialog_in_Acrobat); 
     IntPtr hwnd = IntPtr.Zero; 
     for (int i = 0; i < ChildPtrList.Count; i++) 
     { 
      StringBuilder sClass = new StringBuilder(); 
      GetClassName(ChildPtrList[i], sClass, 100); 
      if (sClass.ToString() == "ComboBox") 
      { 
       comboBoxCount++; 
       if (comboBoxCount == HWND_PRINTER_NAME) 
       { 
        hwnd = ChildPtrList[i]; 
        break; 
       } 
      } 
     } 
     ChildPtrList.Clear(); 

     int sSize; 
     sSize = (int)SendMessage(hwnd, WM_GETTEXTLENGTH, IntPtr.Zero, IntPtr.Zero) + 1; 

     StringBuilder sbTitle = new StringBuilder(sSize); 
     SendMessage(hwnd, WM_GETTEXT, (IntPtr)sSize, sbTitle); 
     return (sbTitle.ToString()); 
    } 

    #region Code from http://pinvoke.net/default.aspx/user32/EnumChildWindows.html 
    [DllImport("user32")] 
    [return: MarshalAs(UnmanagedType.Bool)] 
    public static extern bool EnumChildWindows(IntPtr window, EnumWindowProc callback, IntPtr i); 

    /// <summary> 
    /// Returns a list of child windows 
    /// </summary> 
    /// <param name="parent">Parent of the windows to return</param> 
    /// <returns>List of child windows</returns> 
    public static List<IntPtr> GetChildWindows(IntPtr parent) 
    { 
     List<IntPtr> result = new List<IntPtr>(); 
     GCHandle listHandle = GCHandle.Alloc(result); 
     try 
     { 
      EnumWindowProc childProc = new EnumWindowProc(EnumWindow); 
      EnumChildWindows(parent, childProc, GCHandle.ToIntPtr(listHandle)); 
     } 
     finally 
     { 
      if (listHandle.IsAllocated) 
       listHandle.Free(); 
     } 
     return result; 
    } 

    /// <summary> 
    /// Callback method to be used when enumerating windows. 
    /// </summary> 
    /// <param name="handle">Handle of the next window</param> 
    /// <param name="pointer">Pointer to a GCHandle that holds a reference to the list to fill</param> 
    /// <returns>True to continue the enumeration, false to bail</returns> 
    private static bool EnumWindow(IntPtr handle, IntPtr pointer) 
    { 
     GCHandle gch = GCHandle.FromIntPtr(pointer); 
     List<IntPtr> list = gch.Target as List<IntPtr>; 
     if (list == null) 
     { 
      throw new InvalidCastException("GCHandle Target could not be cast as List<IntPtr>"); 
     } 
     list.Add(handle); 
     // You can modify this to check to see if you want to cancel the operation, then return a null here 
     return true; 
    } 

    /// <summary> 
    /// Delegate for the EnumChildWindows method 
    /// </summary> 
    /// <param name="hWnd">Window handle</param> 
    /// <param name="parameter">Caller-defined variable; we use it for a pointer to our list</param> 
    /// <returns>True to continue enumerating, false to bail.</returns> 
    public delegate bool EnumWindowProc(IntPtr hWnd, IntPtr parameter); 
    #endregion 

} 
}