DELPHI实现activex控件的限制

个人认为DELPHI实现activex控件的限制存在于DELPHI的activex控件的基类派生于TAutoObject如下：

TActiveXControl = class(TAutoObject,

IConnectionPointContainer,

IDataObject,

IObjectSafety,

IOleControl,

IOleInPlaceActiveObject,

IOleInPlaceObject,

IOleObject,

iperPRopertyBrowsing,

IPersistPropertyBag,

IPersistStorage,

IPersistStreamInit,

IQuickActivate,

ISimpleFrameSite,

ISpecifyPropertyPages,

IViewObject,

IViewObject2)

....

....

end;

用DELPHI制作过activex控件的人都知道DELPHI的activex控件向导中必须指明控件包含的VCL窗体控件（从TWinControl派生的VCL控件），这样就使得它的实现必须包含一个VCL窗体控件，而为了让这个VCL窗体控件随时可用DELPHI还要为该控件提供一个父窗口。看下面代码：

procedure TActiveXControl.Initialize;

begin

inherited Initialize;

FConnectionPoints := TConnectionPoints.Create(Self);

FControlFactory := Factory as TActiveXControlFactory;

if FControlFactory.EventTypeInfo <> nil then

FConnectionPoints.CreateConnectionPoint(FControlFactory.EventIID,

ckSingle, EventConnect);

FPropertySinks := FConnectionPoints.CreateConnectionPoint(IPropertyNotifySink,

ckMulti, nil);

FControl := FControlFactory.WinControlClass.CreateParented(ParkingWindow);

if csReflector in FControl.ControlStyle then

FWinControl := TReflectorWindow.Create(ParkingWindow, FControl) else

FWinControl := FControl;

FControlWndProc := FControl.WindowProc;

FControl.WindowProc := WndProc;

InitializeControl;

end;

这就是DELPHI实现activex控件的限制，我们如何去控制这个ParkingWindow，就算能够控制整个activex控件的体积以及膨胀了很多了，在internet上的activex控件越小越好，至少现在的DELPHI要实现类似vc轻量级控件（只实现IPersistStreamInit，IOleControl，IOleObject，IOleInPlaceActiveObject，IViewObjectEx，IOleInPlaceObjectWindowless这些接口的COM对象）非常困难，更不要说要按需（根据activex控件的使用范围是IE还是Word或者其他）实现接口了。一种解决方案就是不从TAutoObject派生而是直接从窗体控件派生如下：

TMyActiveXControl=class(TMyControl,

//TMyControl是一般的类也可以是VCL窗体控件类.

//下面的接口并不总是需要派生和实现。可按需派生和实现

IConnectionPointContainer,

IDataObject,

IObjectSafety,

IOleControl,

IOleInPlaceActiveObject,

IOleInPlaceObject,

IOleObject,

IPerPropertyBrowsing,

IPersistPropertyBag,

IPersistStorage,

IPersistStreamInit,

IQuickActivate,

ISimpleFrameSite,

ISpecifyPropertyPages,

IViewObject,

IViewObject2)

....

....

end;

但是如果这样，新的问题又产生了，如何注册这个activex控件呢？因为没有合适的类厂对象，DELPHI的类厂是如下关系：

TComObjectFactory-->TTypedComObjectFactory-->TAutoObjectFactory

-->TActiveXControlFactory-->TActiveFormFactory

而TComObjectFactory是这样实现的，

TComObject = class(TObject, IUnknown, ISupportErrorInfo)

。。。。

End;

TComClass = class of TComObject;

TComObjectFactory = class(TObject, IUnknown, IClassFactory, IClassFactory2)

…..

constructor Create(ComServer: TComServerObject; ComClass: TComClass;

const ClassID: TGUID; const ClassName, Description: string;

Instancing: TClassInstancing; ThreadingModel: TThreadingModel = tmSingle);

End;

类厂的构造函数要求ComClass这个参数，而TComObject是从TObject派生的，因此如我们根本找不到合适的类厂基类来派生，除非有下面的delphi实现：

TMyComObject = class(TMyControl, IUnknown, ISupportErrorInfo)

。。。。

End;

TMyComClass = class of TMyComObject;

TMyComObjectFactory = class(TObject, IUnknown, IClassFactory, IClassFactory2)

…..

constructor Create(ComServer: TComServerObject; MyComClass: TMyComClass;

const ClassID: TGUID; const ClassName, Description: string;

Instancing: TClassInstancing; ThreadingModel: TThreadingModel = tmSingle);

End;

可惜就算有这样的一个类我们也无法使用，这个限制来自于DELPHI对COM类厂的实现如下：

TComServer = class(TComServerObject)

Private

。。。。

procedure FactoryFree(Factory: TComObjectFactory);

procedure FactoryRegisterClassObject(Factory: TComObjectFactory);

procedure FactoryUpdateRegistry(Factory: TComObjectFactory);

procedure LastReleased;

end;

问题就出在这几个函数，这几个函数要求参数是TComObjectFactory类型，也就是说要使用delphi提供的COM服务器的实现，那么COM对象的类厂就必须从TComObjectFactory派生，我没想通这儿为什么不使用接口，比如是如下实现：

TComServer = class(TComServerObject)

Private

。。。。

procedure FactoryFree(Factory: IClassFactory);

procedure FactoryRegisterClassObject(Factory: IClassFactory);

procedure FactoryUpdateRegistry(Factory: IClassFactory);

procedure LastReleased;

end;