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c++ – AccessibleObjectFromWindow returns an E_FAIL code

Posted by: admin April 23, 2020 Leave a comment

Questions:

Please review the following code, which is supposed to connect to Excel currently running:

#include <windows.h>
#include <oleacc.h>
#import "C:\Program Files (x86)\Common Files\microsoft shared\OFFICE14\MSO.DLL" no_implementation rename("RGB", "ExclRGB") rename("DocumentProperties", "ExclDocumentProperties") rename("SearchPath", "ExclSearchPath")
#import "C:\Program Files (x86)\Common Files\microsoft shared\VBA\VBA6\VBE6EXT.OLB" no_implementation
#import "C:\Program Files (x86)\Microsoft Office\Office14\EXCEL.EXE" rename("DialogBox", "ExclDialogBox") rename("RGB", "ExclRGB") rename("CopyFile", "ExclCopyFile") rename("ReplaceText", "ExclReplaceText")

BOOL CALLBACK EnumChildProc(HWND hwnd, LPARAM)
{
   WCHAR szClassName[64];
   if(GetClassNameW(hwnd, szClassName, 64))
   {
      if(_wcsicmp(szClassName, L"EXCEL7") == 0)
      {
         //Get AccessibleObject
         Excel::Window* pWindow = NULL;
         HRESULT hr = AccessibleObjectFromWindow(hwnd, OBJID_NATIVEOM, __uuidof(Excel::Window), (void**)&pWindow);
         if(hr == S_OK)
         {
            //Excel object is now in pWindow pointer, from this you can obtain the document or application
            Excel::_Application* pApp = NULL;
            pApp = pWindow->GetApplication();
            pWindow->Release();
         }
         return false;     // Stops enumerating through children
      }
   }
   return true;
}

int main( int argc, CHAR* argv[])
{
    //The main window in Microsoft Excel has a class name of XLMAIN
    HWND excelWindow = FindWindow(L"XLMAIN", NULL);
    //Use the EnumChildWindows function to iterate through all child windows until we find _WwG
    EnumChildWindows(excelWindow, (WNDENUMPROC) EnumChildProc, (LPARAM)1);
    return 0;
}

The truth is Excel really running in current moment, but AccessibleObjectFromWindow returns E_FAIL.
I also tried to run this code in a loop and switch to Excel to it focused application. The same story, AccessibleObjectFromWindow returns an E_FAIL.
I am now searching in the internet for an answer but all found before gave me nothing. So if someone could provide an explanation it would be greatly appreciated.

How to&Answers:

Found an answer from some code example:

int main( int argc, CHAR* argv[])
{
    CoInitialize( NULL );
    ...

The problem is resolved with CoInitialize(NULL) call before starting work with any other objects.