VC++编程常见问题解答十九


问：RegisterWindowMessage中的BroadcastSystemMessage如何处理?


我想用BroadcastSystemMessage来在两个进程之间通讯,我从一个进程发送了一个
用 RegisterWindowMessage注册过的消息,但在目的进程中却没有收到该消息.
答：我认为你应该在两个进程的最高级窗口中都注册该消息.请看下例:


static UINT sBroadcastCommand = ::RegisterWindowMessage( _T("BroadcastCommand"));
BEGIN_MESSAGE_MAP( Gui_Top_Level_MainFrame, Gui_MainFrame )
    ON_REGISTERED_MESSAGE( sBroadcastCommand, onBroadcastCommand )
END_MESSAGE_MAP()
LRESULT Gui_MainFrame :: onBroadcastCommand( UINT aMsg, LPARAM lParam )
{
    your code...
}

然后发送进行应该包含:

While the sending process would contain:
static UINT sBroadcastCommand = ::RegisterWindowMessage( _T("BroadcastCommand"));
void Someclass :: someMethod( void )
    {
    ::PostMessage( (HWND)HWND_BROADCAST,sBroadcastCommand, 0,yourMessageId );
    }

问：CListCtrl中选择变化时如何获得通知?


我在Report View中使用了一个CListCtrl(自绘制类型),我想知道什么时候选择项 发生了改变.
答：在选择项变化时,可以使用按钮有效或失效,按如下操作:


  加入LVN_ITEMCHANGED消息处理.
 void CYourClassNameHere::OnItemchangedEventList(NMHDR* pNMHDR, LRESULT* pResult)
{
 NM_LISTVIEW* pNMListView = (NM_LISTVIEW*)pNMHDR;
 *pResult = 0;

 if (pNMListView->uChanged == LVIF_STATE)
 {
  if (pNMListView->uNewState)
   GetDlgItem(IDC_DELETE)->EnableWindow(TRUE);
  else
   GetDlgItem(IDC_DELETE)->EnableWindow(FALSE);
 }
}

问：如何向ATL-COM对象传送一个数组?


我想创建一个函数来向ATL-COM对象传送数组.
答：如下代码的方法用于ACTIVEX中,可能对ATL-COM也有启发吧.


CoInitialize(NULL);
 CLSID m_clsid;
 USES_CONVERSION;
 ::CLSIDFromString(T2OLE("ROUNDANALOG.RoundAnlgAARCtrl.1"), &m_clsid);
 IDispatch FAR* pObj = (IDispatch FAR*)NULL;
 CString str = "UpdateControl";
 BSTR bstr = str.AllocSysString();
 HRESULT hr = CoCreateInstance(m_clsid, NULL, CLSCTX_ALL, IID_IDispatch,
(void**)&pObj);

 SafeArrayAccessData(psa, (void**)&bstrArray);
 bstrArray[0] = str.AllocSysString();
 bstrArray[1] = str.AllocSysString();
 SafeArrayUnaccessData(psa);

VARIANTARG* pvars = new VARIANTARG[1];
 VariantInit(&pvars[0]);
 pvars[0].vt = VT_ARRAY|VT_BYREF|VT_BSTR;
 pvars[0].pparray = &psa;
 DISPID dispid;

 hr = pObj->GetIDsOfNames(IID_NULL, &bstr, 1,LOCALE_USER_DEFAULT, &dispid);

DISPPARAMS disp = {pvars, &dispid, 1,1};
 hr = pObj->Invoke(dispid, IID_NULL,
LOCALE_USER_DEFAULT,DISPATCH_PROPERTYPUT,&disp,NULL, NULL, NULL);
 delete[] pvars;
 pObj->Release();
 CoUninitialize();

在你的控制中建立如下函数:

void CRoundAnlgAARCtrl::SaveFunc(const VARIANT FAR& var)
{
 // TODO: Add your dispatch handler code here
 ASSERT(var.vt == VT_ARRAY | VT_BYREF | VT_BSTR);
 SAFEARRAY* psa = *var.pparray;
}

问：如何选择CTreeCtrl中的节点文本进行编辑?


在向CTreeCtrl中加入一项后,有什么方法可以编辑该节点的文本呢?
答：首先设置你的CcompTreeCtrl具有TVS_EDITLABELS属性.在设计时用控件属性
来设置 在运行时用GetStyle()/SetStyle()成员函数来设置.然后请看下述代码:


HTREEITEM CCompTreeCtrl::AddSet()
{
static int setCnt =3D 1;
HTREEITEM hItem;
CString csSet;

//create text for new note: New Set 1, New Set 2 ...
csSet.Format( _T( "New Set %d" ), setCnt++ );

hItem =3D InsertItem( csSet, IMG_CLOSEDFOLDER, IMG_CLOSEDFOLDER );

if( hItem !=3D NULL )
           EditLabel( hItem );

return hItem;
}