通过ActiveX client 取消（cancel)一个命令

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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. 
   
3. void SendCmdToAcad(CString& cmd)
   
4. {
   
5.             COPYDATASTRUCT cmdMsg;
   
6.             cmdMsg.dwData = (DWORD)1;
   
7.             cmdMsg.cbData = (DWORD)_tcslen(cmd) + 1;
   
8.             cmdMsg.lpData = cmd.GetBuffer(cmd.GetLength()+1) ;
   
9. 
   
10.             SendMessage(HWND_ACAD, WM_COPYDATA, NULL, (LPARAM)&cmdMsg);
    
11. }
    
12. 
    
13. void doCancel()
    
14. {
    
15.             CString txt = "\x1B\x1B";
    
16.             SendCmdToAcad(txt);
    
17. }
    

HWND HWND_ACAD;<br /> <br /> void SendCmdToAcad(CString& cmd)<br /> {<br />             COPYDATASTRUCT cmdMsg;<br />             cmdMsg.dwData = (DWORD)1;<br />             cmdMsg.cbData = (DWORD)_tcslen(cmd) + 1;<br />             cmdMsg.lpData = cmd.GetBuffer(cmd.GetLength()+1) ;<br /> <br />             SendMessage(HWND_ACAD, WM_COPYDATA, NULL, (LPARAM)&cmdMsg);<br /> }<br /> <br /> void doCancel()<br /> {<br />             CString txt = "\x1B\x1B";<br />             SendCmdToAcad(txt);<br /> }<br />

The trick is to find the AutoCAD window handle on the desktop. To do this,
traverse the Windows desktop to locate AutoCAD.

1. CString GetWindowTitle(HWND &hwnd)
   
2. {
   
3.             char s[256];
   
4.             if (!::GetWindowText(hwnd, s, sizeof(s)))
   
5.                         return "";                       // ignore empty titles
   
6.             else
   
7.                         return s;
   
8. }
   
9. 
   
10. void SendCmdToAcad(CString& cmd)
    
11. {
    
12.             COPYDATASTRUCT cmdMsg;
    
13.             cmdMsg.dwData = (DWORD)1;
    
14.             cmdMsg.cbData = (DWORD)_tcslen(cmd) + 1;
    
15.             cmdMsg.lpData = cmd.GetBuffer(cmd.GetLength()+1) ;
    
16. 
    
17.             SendMessage(HWND_ACAD, WM_COPYDATA, NULL, (LPARAM)&cmdMsg);
    
18. }
    
19. 
    
20. BOOL CALLBACK EnumWindowsProc(HWND hwnd, LPARAM lParam)
    
21. {
    
22.             CString title = GetWindowTitle(hwnd);
    
23.             if(title == "")
    
24.                         return TRUE;
    
25.             if(title.Find("AutoCAD") != -1)
    
26.             {
    
27.                         HWND_ACAD = hwnd;
    
28.                         return FALSE;
    
29.             }
    
30.             else
    
31.                         return TRUE;
    
32. }
    
33. 
    
34. BOOL FindAcadFrameWnd()
    
35. {
    
36.             //WNDENUMPROC lpEnumFunc = NULL;
    
37.             if(EnumWindows((WNDENUMPROC) EnumWindowsProc, NULL))
    
38.                         return TRUE;
    
39.             else
    
40.                         return FALSE;
    
41. }
    

CString GetWindowTitle(HWND &hwnd)<br /> {<br />             char s[256];<br />             if (!::GetWindowText(hwnd, s, sizeof(s)))<br />                         return "";                       // ignore empty titles<br />             else<br />                         return s;<br /> }<br /> <br /> void SendCmdToAcad(CString& cmd)<br /> {<br />             COPYDATASTRUCT cmdMsg;<br />             cmdMsg.dwData = (DWORD)1;<br />             cmdMsg.cbData = (DWORD)_tcslen(cmd) + 1;<br />             cmdMsg.lpData = cmd.GetBuffer(cmd.GetLength()+1) ;<br /> <br />             SendMessage(HWND_ACAD, WM_COPYDATA, NULL, (LPARAM)&cmdMsg);<br /> }<br /> <br /> BOOL CALLBACK EnumWindowsProc(HWND hwnd, LPARAM lParam)<br /> {<br />             CString title = GetWindowTitle(hwnd);<br />             if(title == "")<br />                         return TRUE;<br />             if(title.Find("AutoCAD") != -1)<br />             {<br />                         HWND_ACAD = hwnd;<br />                         return FALSE;<br />             }<br />             else<br />                         return TRUE;<br /> }<br /> <br /> BOOL FindAcadFrameWnd()<br /> {<br />             //WNDENUMPROC lpEnumFunc = NULL;<br />             if(EnumWindows((WNDENUMPROC) EnumWindowsProc, NULL))<br />                         return TRUE;<br />             else<br />                         return FALSE;<br /> }<br />

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. 
   
3. Private Sub GetAcadObj_Click()
   
4.    On Error Resume Next
   
5.    Const acadAppName = "AutoCAD.Application"
   
6.    Set AcadObj = GetObject(, acadAppName)
   
7.    If Err Then
   
8.             Err.Clear
   
9.             Set AcadObj = CreateObject(acadAppName)
   
10.             If Err Then
    
11.                 MsgBox Err.Source
    
12.                 Exit Sub
    
13.             End If
    
14.    End If
    
15. 
    
16.    AcadObj.Visible = True 'hidden by default after creation
    
17. End Sub
    
18. 
    
19. Private Sub CancelCmd_Click()
    
20.    Dim cmdStr
    
21.    cmdStr = Chr(27) + Chr(27)
    
22.    AppActivate AcadObj.Application.Caption
    
23.    SendKeys cmdStr, True
    
24. End Sub
    
25. 
    

dim AcadObj as Object<br /> <br /> Private Sub GetAcadObj_Click()<br />    On Error Resume Next<br />    Const acadAppName = "AutoCAD.Application"<br />    Set AcadObj = GetObject(, acadAppName)<br />    If Err Then<br />             Err.Clear<br />             Set AcadObj = CreateObject(acadAppName)<br />             If Err Then<br />                 MsgBox Err.Source<br />                 Exit Sub<br />             End If<br />    End If<br /> <br />    AcadObj.Visible = True 'hidden by default after creation<br /> End Sub<br /> <br /> Private Sub CancelCmd_Click()<br />    Dim cmdStr<br />    cmdStr = Chr(27) + Chr(27)<br />    AppActivate AcadObj.Application.Caption<br />    SendKeys cmdStr, True<br /> End Sub<br /> <br />

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.

To find the handle of the AutoCAD, see DevNote #1610.

See these related solutions:
DevNote #1610
DevNote #2855
DevNote #2549
DevNote #17088