DELPHI实现activex控件的限制
2006-02-04 13:42:26 来源:WEB开发网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:
-->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;
追根到底问题出在delphi提供的COM服务器的实现以及类厂的实现上了,这下就没法了,至少我现在还没有找到什么好办法,现在想到的就只有自己实现COM服务器dll以及自己的activex控件类工厂了(实际上也做了一个,感觉还是很简单,有些delph实现COM服务器的的方法可以直接使用)。更多精彩
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