这是我最近的做法。在你的IDL中添加一个实现IDispatch接口的接口和一个该接口的coclass:
[
object,
uuid(6EDA5438-0915-4183-841D-D3F0AEDFA466),
nonextensible,
oleautomation,
pointer_default(unique)
]
interface IServerEvents : IDispatch
{
[id(1)]
HRESULT OnServerEvent();
}
[
uuid(FA8F24B3-1751-4D44-8258-D649B6529494),
]
coclass ServerEvents
{
[default] interface IServerEvents;
[default, source] dispinterface IServerEvents;
};
这是CServerEvents类的声明:
class ATL_NO_VTABLE CServerEvents :
public CComObjectRootEx<CComSingleThreadModel>,
public CComCoClass<CServerEvents, &CLSID_ServerEvents>,
public IDispatchImpl<IServerEvents, &IID_IServerEvents , &LIBID_YourLibrary, -1, -1>,
public IConnectionPointContainerImpl<CServerEvents>,
public IConnectionPointImpl<CServerEvents,&__uuidof(IServerEvents)>
{
public:
CServerEvents()
{
}
BEGIN_COM_MAP(CServerEvents)
COM_INTERFACE_ENTRY(IServerEvents)
COM_INTERFACE_ENTRY(IDispatch)
COM_INTERFACE_ENTRY(IConnectionPointContainer)
END_COM_MAP()
BEGIN_CONNECTION_POINT_MAP(CServerEvents)
CONNECTION_POINT_ENTRY(__uuidof(IServerEvents))
END_CONNECTION_POINT_MAP()
STDMETHOD(OnServerEvent)();
private:
CRITICAL_SECTION m_csLock;
};
关键在于实现IConnectionPointImpl和IConnectionPointContainerImpl接口以及连接点映射。OnServerEvent方法的定义如下:
STDMETHODIMP CServerEvents::OnServerEvent()
{
::EnterCriticalSection( &m_csLock );
IUnknown* pUnknown;
for ( unsigned i = 0; ( pUnknown = m_vec.GetAt( i ) ) != NULL; ++i )
{
CComPtr<IDispatch> spDisp;
pUnknown->QueryInterface( &spDisp );
if ( spDisp )
{
spDisp.Invoke0( CComBSTR( L"OnServerEvent" ) );
}
}
::LeaveCriticalSection( &m_csLock );
return S_OK;
}
您需要为客户端提供一种指定事件处理程序的方式。您可以使用像“SetHandler”这样的专用方法来实现,但我更喜欢将处理程序作为异步调用的方法的参数。这样,用户只需要调用一个方法:
STDMETHOD(DoSomethingAsynchronous)( IServerEvents *pCallback );
存储IServerEvents指针,当您想触发事件时,只需调用该方法:
m_pCallback->OnServerEvent();
关于VB代码,处理事件的语法与您所建议的略有不同:
Private m_server As Server
Private WithEvents m_serverEvents As ServerEvents
Private Sub MainMethod()
Set s = CreateObject("Server")
Set m_serverEvents = New ServerEvents
Call m_searchService.DoSomethingAsynchronous(m_serverEvents)
End Sub
Private Sub m_serverEvents_OnServerEvent()
MsgBox "Event handled"
End Sub
我希望这能有所帮助。