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Cancelling a command through an ActiveX client

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发表于 2021-1-11 22:43:59 | 显示全部楼层 |阅读模式

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问题:

If I send commands to the AutoCAD command line from an external VB application
using Windows' API functions such as SendKeys or SendMessage, this works except
when another command is busy. How can I cancel this command? If I send an Escape
(27) or an CTRL-C, I don't get any results. The escape character is send to the
AutoCAD window, but this only happens after I cancel the command by pressing the
Escape key.

解答:

Through an ActiveX client that is written in C++ or VB code, you should always
be able to cancel an active AutoCAD command at the command line.

From a client application written in C++, the following code cancels an active
AutoCAD command at the command line even with transparent commands.


  1. HWND HWND_ACAD;

  2. void SendCmdToAcad(CString& cmd)
  3. {
  4.     COPYDATASTRUCT cmdMsg;
  5.     cmdMsg.dwData = (DWORD)1;
  6.     cmdMsg.cbData = (DWORD)_tcslen(cmd) + 1;
  7.     cmdMsg.lpData = cmd.GetBuffer(cmd.GetLength()+1) ;

  8.     SendMessage(HWND_ACAD, WM_COPYDATA, NULL, (LPARAM)&cmdMsg);
  9. }

  10. void doCancel()
  11. {
  12.     CString txt = "\x1B\x1B";
  13.     SendCmdToAcad(txt);
  14. }
  15. The trick is to find the AutoCAD window handle on the desktop. To do this,
  16. traverse the Windows desktop to locate AutoCAD.


  17. CString GetWindowTitle(HWND &hwnd)
  18. {
  19.     char s[256];
  20.     if (!::GetWindowText(hwnd, s, sizeof(s)))
  21.         return "";          // ignore empty titles
  22.     else
  23.         return s;
  24. }

  25. void SendCmdToAcad(CString& cmd)
  26. {
  27.     COPYDATASTRUCT cmdMsg;
  28.     cmdMsg.dwData = (DWORD)1;
  29.     cmdMsg.cbData = (DWORD)_tcslen(cmd) + 1;
  30.     cmdMsg.lpData = cmd.GetBuffer(cmd.GetLength()+1) ;

  31.     SendMessage(HWND_ACAD, WM_COPYDATA, NULL, (LPARAM)&cmdMsg);
  32. }

  33. BOOL CALLBACK EnumWindowsProc(HWND hwnd, LPARAM lParam)
  34. {
  35.     CString title = GetWindowTitle(hwnd);
  36.     if(title == "")
  37.         return TRUE;
  38.     if(title.Find("AutoCAD") != -1)
  39.     {
  40.         HWND_ACAD = hwnd;
  41.         return FALSE;
  42.     }
  43.     else
  44.         return TRUE;
  45. }

  46. BOOL FindAcadFrameWnd()
  47. {
  48.     //WNDENUMPROC lpEnumFunc = NULL;
  49.     if(EnumWindows((WNDENUMPROC) EnumWindowsProc, NULL))
  50.         return TRUE;
  51.     else
  52.         return FALSE;
  53. }


The preceding code resides in an ActiveX client application. More specifically,
it is a dialog based MFC AppWizard EXE. The attached project shows all the code.

In a client written in VB code, make sure you call AppActivate before you use
SendKeys(). Otherwise the string is sent to whatever window is active, which may
not always be the AutoCAD window.

  1. dim AcadObj as Object

  2. Private Sub GetAcadObj_Click()
  3.    On Error Resume Next
  4.    Const acadAppName = "AutoCAD.Application"
  5.    Set AcadObj = GetObject(, acadAppName)
  6.    If Err Then
  7.     Err.Clear
  8.     Set AcadObj = CreateObject(acadAppName)
  9.     If Err Then
  10.         MsgBox Err.Source
  11.         Exit Sub
  12.     End If
  13.    End If

  14.    AcadObj.Visible = True 'hidden by default after creation
  15. End Sub

  16. Private Sub CancelCmd_Click()
  17.    Dim cmdStr
  18.    cmdStr = Chr(27) + Chr(27)
  19.    AppActivate AcadObj.Application.Caption
  20.    SendKeys cmdStr, True
  21. End Sub


You can also convert the preceding C++ code to VB code to achieve the same
results. SendKeys() seems to be much easier in this case.

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