使用可連接物件

HRESULT AdviseFREngineObject( IUnknown* object, IUnknown* callback, DWORD* cookie );
HRESULT UnAdviseFREngineObject( IUnknown* object, DWORD cookie );
class CFRDocumentCallback: public IFRDocumentEvents {
public:
...
    // 提供 IUnknown 方法的簡單實作
    ULONG STDMETHODCALLTYPE AddRef() { return 1; }
    ULONG STDMETHODCALLTYPE Release() { return 1; }
    HRESULT STDMETHODCALLTYPE QueryInterface( REFIID riid, void** ppObject )
    {
        if( ppObject == 0 ) {
            return E_POINTER;
        }
    *ppObject = 0;
    if( riid == IID_IUnknown || riid == IID_IFRDocumentEvents )
    {
        *ppObject = this;
        AddRef();
        return S_OK;
    } else {
        return E_NOINTERFACE;
    }
}
// 提供 IFRDocumentEvents 方法的實作
HRESULT STDMETHODCALLTYPE OnProgress(
IFRDocument* sender, int percentage, VARIANT_BOOL* cancel );
HRESULT STDMETHODCALLTYPE OnWarning(
IFRDocument* sender, int index, BSTR tip, VARIANT_BOOL* cancel );
HRESULT STDMETHODCALLTYPE OnPageProcessed(
    IFRDocument* sender, int index, PageProcessingStageEnum stage ) { return S_OK; }
};
// 假設我們已經取得 FRDocument 物件
IFRDocument* document;
// 建立回呼物件
CFRDocumentCallback callbackObject;
// 將接聽器註冊至通知來源
DWORD cookie; // 用於儲存來自 Advise 方法的 cookie 的變數
AdviseFREngineObject( frDocument, &callbackObject, &cookie );
// 處理文件
...
// 處理完成後，不再需要接聽器，因此應取消註冊
UnadviseFREngineObject( frDocument, cookie );

Private WithEvents document As FREngine.FRDocument
Private Sub document_RecognitionOnProgress(ByVal sender As FREngine.FRDocument, _
                                           ByVal Percentage As Integer, _
                                           ByRef cancel As Boolean)
...
End Sub
Private Sub document_RecognitionOnProgress(ByVal sender As FREngine.FRDocument, _
                                           ByVal Percentage As Integer, _
                                           ByRef cancel As Boolean) Handles document.OnProgress
...
End Sub
document = Engine.CreateFRDocument
document.AddImageFile("D:\Demo.tif")
AddHandler document.OnProgress, AddressOf Me.document_RecognitionOnProgress
document.Process()
RemoveHandler document.OnProgress, AddressOf Me.document_RecognitionOnProgress
或者，如果您使用 Handles 關鍵字定義事件處理方法，則可直接使用 FRDocument 物件進行處理：
document = Engine.CreateFRDocument
document.AddImageFile("D:\Demo.tif")
document.Process()

class CFRDocumentEventsListener : public IFRDocumentEvents {
public:
...
    // 提供 IUnknown 方法的簡單實作。這些方法也可以
    // 透過繼承某個支援 COM 的標準類別來實作
    ULONG AddRef();
    ULONG Release();
    HRESULT QueryInterface(REFIID riid, void** ppvObject)
    {
        if( ppvObject == 0 )
            return E_INVALIDARG;
        if( riid == __uuidof(IFRDocumentEvents) ) {
            *ppvObject = static_cast<IFRDocumentEvents*>( this );
        } else if( riid == IID_IUnknown ) {
            *ppvObject = static_cast<IUnknown*>( this );
        } else {
            *ppvObject = 0;
            return E_NOINTERFACE;
        }
        AddRef();
        return S_OK;
    }
    // 提供 IFRDocumentEvents 方法的實作
 HRESULT STDMETHODCALLTYPE OnProgress(
  IFRDocument* sender, int percentage, VARIANT_BOOL* cancel );
 HRESULT STDMETHODCALLTYPE OnWarning(
  IFRDocument* sender, int index, BSTR tip, VARIANT_BOOL* cancel );
 HRESULT STDMETHODCALLTYPE OnPageProcessed(
  IFRDocument* sender, int index, PageProcessingStageEnum stage ) { return S_OK; }
};
// 假設我們已經取得 FRDocument 物件
IFRDocument* document;
// 在 FRDocument 物件上查詢 IConnectionPointContainer
IConnectionPointContainer* pContainer=0;
document->QueryInterface(IID_IConnectionPointContainer, (void**)&pContainer);
// 取得可連接物件中某個連接點上的 IConnectionPoint 介面指標
IConnectionPoint* pPoint=0;
pContainer->FindConnectionPoint(__uuidof(IFRDocumentEvents),
                                &pPoint);
// 在 CFRDocumentEventsListener 類別與連接點之間建立連線
CFRDocumentEventsListener listener;
IUnknown* listenerUnknown=0;
listener.QueryInterface(IID_IUnknown, (void**)&listenerUnknown);
// 將 listener Advise 至通知來源
DWORD cookie; // 用來儲存 IConnectionPoint::Advise 方法所傳回 cookie 的變數
pPoint->Advise(listenerUnknown, &cookie);
// 處理文件
...
// 通知完成後，listener 就不再需要，應取消 Advise
pPoint->Unadvise(cookie);

private void document_RecognitionOnProgress(FREngine.IFRDocument sender, int Percentage, ref bool cancel)
{
 ...
}
FREngine.DIFRDocumentEvents_OnProgressEventHandler recognizeOnProgressHandler =
 new FREngine.DIFRDocumentEvents_OnProgressEventHandler(
 document_RecognitionOnProgress );
document.OnProgress += recognizeOnProgressHandler;
document.Process( null, null, null );
document.OnProgress -= recognizeOnProgressHandler;