就是如何使IE扩展组件可以响应事件。
在自己的程序中使用过WebBrowser控件的朋友都知道，WebBrowser控件定义了诸如BeforeNavigate、DownloadComplete 等事件，我们可以通过编写事件处理代码实现对WebBrowser控件的操作。那么如何实现对IE的事件响应和处理呢？同建立IE面板一样。我们需要建立一个实现IObjectWithSite接口的COM组件，不同的是，我们还需要实现IDispatch接口，在IObjectWithSite接口的SetSite方法中获得IE的WebBrowser接口并建立自身与WebBrowser的连接，然后如果在IE的Webbrowser对象中发生什么事件的话，那么IE就会回调连接的IDispatch接口的Invoke方法。我们通过在Invoke方法中编写代码就可以获得IE事件了。这个利用的是COM编程的回调接口原理。
下面我们首先来实现代码。点击Delphi菜单 File | New 。在 ActiveX 页面中选择Active Library ，然后点击 OK 按钮。然后用同样的方法建立一个COM Object。在COM Object Wizard 窗口中，将复选框 Included type library 去掉。然后在Class Name中输入IEHelper，在Implemented Interface 中输入：IDispatch；IObjectwithSite 。然后点击 OK 按钮建立一个COM组件。
保存工程，将工程保存为IEHelper.dpr，将Unit1保存为IEHelperUnit.pas。下面是IEHelperUnit.pas的具体代码：
unit iehelperunit; interface uses WIndows, Comobj, ActiveX, SHDOCVW, MSHTML,Dialogs; type TIEHelperFactory = class(TComObjectFactory) private procedure AddKeys; procedure RemoveKeys; public procedure UpdateRegistry(Register: Boolean); override; end; TIEHelper = class(TComObject, IDispatch, IObjectWithSite) public function GetTypeInfoCount(out Count: Integer): HResult; stdcall; function GetTypeInfo(Index, LocaleID: Integer; out TypeInfo): HResult; stdcall; function GetIDsOfNames(const IID: TGUID; Names: Pointer; NameCount, LocaleID: Integer; DispIDs: Pointer): HResult; stdcall; function Invoke(DispID: Integer; const IID: TGUID; LocaleID: Integer; Flags: Word; var Params; VarResult, ExcepInfo, ArgErr: Pointer): HResult; stdcall; function SetSite(const pUnkSite: IUnknown): HResult; stdcall; function GetSite(const riid: TIID; out site: IUnknown): HResult; stdcall; private IE: IWebbrowser2; Cookie: Integer; end; const Class_IEHelper: TGUID = {3D898C55-74CC-4B7C-B5F1-45913F368388}; implementation uses ComServ, Registry, SysUtils; procedure DoStatusTextChange(const Text: WideString); begin end; procedure DoProgressChange(Progress: Integer; ProgressMax: Integer); begin end; procedure DoCommandStateChange(Command: Integer; Enable: WordBool); begin end; procedure DoDownloadBegin; begin end; procedure DoDownloadComplete; begin end; procedure DoTitleChange(const Text: WideString); begin end; procedure DoPropertyChange(const szProperty: WideString); begin end; procedure DoBeforeNavigate2(const pDisp: IDispatch; var URL: OleVariant; var Flags: OleVariant; var TargetFrameName: OleVariant; var PostData: OleVariant; var Headers: OleVariant; var Cancel: WordBool); begin if URL<>http://www.applevb.com/then begin Showmessage(你不可以浏览其它站点); Cancel:=True; URL:=http://www.applevb.com; (pDisp as IWebbrowser2).Navigate2(URL,Flags,TargetFrameName,PostData,Headers); end; end; procedure DoNewWindow2(var ppDisp: IDispatch; var Cancel: WordBool); begin end; procedure DoNavigateComplete2(const pDisp: IDispatch; var URL: OleVariant); begin end; procedure DoDocumentComplete(const pDisp: IDispatch; var URL: OleVariant); begin end; procedure DoOnQuit; begin end; procedure DoOnVisible(Visible: WordBool); begin end; procedure DoOnToolBar(ToolBar: WordBool); begin end; procedure DoOnMenuBar(MenuBar: WordBool); begin end; procedure DoOnStatusBar(StatusBar: WordBool); begin end; procedure DoOnFullScreen(FullScreen: WordBool); begin end; procedure DoOnTheaterMode(TheaterMode: WordBool); begin end; procedure BuildPositionalDispIds(pDispIds: PDispIdList; const dps: TDispParams); var i: integer; begin Assert(pDispIds <> nil); for i := 0 to dps.cArgs - 1 do pDispIds^[i] := dps.cArgs - 1 - i; if (dps.cNamedArgs <= 0) then Exit; for i := 0 to dps.cNamedArgs - 1 do pDispIds^[dps.rgdispidNamedArgs^[i]] := i; end; function TIEHelper.Invoke(DispID: Integer; const IID: TGUID; LocaleID: Integer; Flags: Word; var Params; VarResult, ExcepInfo, ArgErr: Pointer): HResult; type POleVariant = ^OleVariant; var dps: TDispParams absolute Params; bHasParams: boolean; pDispIds: PDispIdList; iDispIdsSize: integer; begin Result := DISP_E_MEMBERNOTFOUND; pDispIds := nil; iDispIdsSize := 0; bHasParams := (dps.cArgs > 0); if (bHasParams) then begin iDispIdsSize := dps.cArgs * SizeOf(TDispId); GetMem(pDispIds, iDispIdsSize); end; try if (bHasParams) then BuildPositionalDispIds(pDispIds, dps); case DispId of 102: begin DoStatusTextChange(dps.rgvarg^[pDispIds^[0]].bstrval); Result := S_OK; end; 108: begin DoProgressChange(dps.rgvarg^[pDispIds^[0]].lval, dps.rgvarg^[pDispIds^[1]].lval); Result := S_OK; end; 105: begin DoCommandStateChange(dps.rgvarg^[pDispIds^[0]].lval, dps.rgvarg^[pDispIds^[1]].vbool); Result := S_OK; end; 106: begin DoDownloadBegin(); Result := S_OK; end; 104: begin DoDownloadComplete(); Result := S_OK; end; 113: begin DoTitleChange(dps.rgvarg^[pDispIds^[0]].bstrval); Result := S_OK; end; 112: begin DoPrtype POleVariant = ^OleVariant; var dps: TDispParams absolute Params; bHasParams: boolean; pDispIds: PDispIdList; iDispIdsSize: integer; begin Result := DISP_E_MEMBERNOTFOUND; pDispIds := nil; iDispIdsSize := 0; bHasParams := (dps.cArgs > 0); if (bHasParams) then begin iDispIdsSize := dps.cArgs * SizeOf(TDispId); GetMem(pDispIds, iDispIdsSize); end; try if (bHasParams) then BuildPositionalDispIds(pDispIds, dps); case DispId of 102: begin DoStatusTextChange(dps.rgvarg^[pDispIds^[0]].bstrval); Result := S_OK; end; 108: begin DoProgressChange(dps.rgvarg^[pDispIds^[0]].lval, dps.rgvarg^[pDispIds^[1]].lval); Result := S_OK; end; 105: begin DoCommandStateChange(dps.rgvarg^[pDispIds^[0]].lval, dps.rgvarg^[pDispIds^[1]].vbool); Result := S_OK; end; 106: begin DoDownloadBegin(); Result := S_OK; end; 104: begin DoDownloadComplete(); Result := S_OK; end; 113: begin DoTitleChange(dps.rgvarg^[pDispIds^[0]].bstrval); Result := S_OK; end; 112: begin DoPropertyChange(dps.rgvarg^[pDispIds^[0]].bstrval); Result := S_OK; end; 250: begin DoBeforeNavigate2(IDispatch(dps.rgvarg^[pDispIds^[0]].dispval), POleVariant(dps.rgvarg^[pDispIds^[1]].pvarval)^, POleVariant(dps.rgvarg^[pDispIds^[2]].pvarval)^, POleVariant(dps.rgvarg^[pDispIds^[3]].pvarval)^, POleVariant(dps.rgvarg^[pDispIds^[4]].pvarval)^, POleVariant(dps.rgvarg^[pDispIds^[5]].pvarval)^, dps.rgvarg^[pDispIds^[6]].pbool^); Result := S_OK; end; 251: begin DoNewWindow2(IDispatch(dps.rgvarg^[pDispIds^[0]].pdispval^), dps.rgvarg^[pDispIds^[1]].pbool^); Result := S_OK; end; 252: begin DoNavigateComplete2(IDispatch(dps.rgvarg^[pDispIds^[0]].dispval), POleVariant(dps.rgvarg^[pDispIds^[1]].pvarval)^); Result := S_OK; end; 259: begin DoDocumentComplete(IDispatch(dps.rgvarg^[pDispIds^[0]].dispval), POleVariant(dps.rgvarg^[pDispIds^[1]].pvarval)^); Result := S_OK; end; 253: begin DoOnQuit(); Result := S_OK; end; 254: begin DoOnVisible(dps.rgvarg^[pDispIds^[0]].vbool); Result := S_OK; end; 255: begin DoOnToolBar(dps.rgvarg^[pDispIds^[0]].vbool); Result := S_OK; end; 256: begin DoOnMenuBar(dps.rgvarg^[pDispIds^[0]].vbool); Result := S_OK; end; 257: begin DoOnStatusBar(dps.rgvarg^[pDispIds^[0]].vbool); Result := S_OK; end; 258: begin DoOnFullScreen(dps.rgvarg^[pDispIds^[0]].vbool); Result := S_OK; end; 260: begin DoOnTheaterMode(dps.rgvarg^[pDispIds^[0]].vbool); Result := S_OK; end; end; finally if (bHasParams) then FreeMem(pDispIds, iDispIdsSize); end; end; function TIEHelper.GetIDsOfNames(const IID: TGUID; Names: Pointer; NameCount, LocaleID: Integer; DispIDs: Pointer): HResult; begin Result := E_NOTIMPL; end; function TIEHelper.GetTypeInfo(Index, LocaleID: Integer; out TypeInfo): HResult; begin Result := E_NOTIMPL; pointer(TypeInfo) := nil; end; function TIEHelper.GetTypeInfoCount(out Count: Integer): HResult; begin Result := E_NOTIMPL; Count := 0; end; function TIEHelper.GetSite(const riid: TIID; out site: IUnknown): HResult; begin // Result := S_OK; if Assigned(IE) then result:=IE.QueryInterface(riid, site) else Result:= E_FAIL; end; function TIEHelper.SetSite(const pUnkSite: IUnknown): HResult; var cmdTarget: IOleCommandTarget; Sp: IServiceProvider; CPC: IConnectionPointContainer; CP: ICOnnectionPoint; begin if Assigned(pUnkSite) then begin cmdTarget := pUnkSite as IOleCommandTarget; Sp := CmdTarget as IServiceProvider; if Assigned(Sp)then Sp.QueryService(IWebbrowserApp, IWebbrowser2, IE); if Assigned(IE) then begin IE.QueryInterface(IConnectionPointContainer, CPC); CPC.FindConnectionPoint(DWEBbrowserEvents2, CP); CP.Advise(Self, Cookie) end; end; Result := S_OK; end; procedure TIEHelperFactory.AddKeys; var S: string; begin S := GUIDToString(CLASS_IEHelper); with TRegistry.Create do try RootKey := HKEY_LOCAL_MACHINE; if OpenKey(SoftwareMicrosoftWindowsCurrentVersionexplorerBrowser Helper Objects + S, TRUE) then CloseKey; finally free; end; end; procedure TIEHelperFactory.RemoveKeys; var S: string; begin S := GUIDToString(CLASS_IEHelper); with TRegistry.Create do try RootKey := HKEY_LOCAL_MACHINE; DeleteKey(SoftwareMicrosoftWindowsCurrentVersionexplorerBrowser Helper Objects + S); finally free; end; end; procedure TIEHelperFactory.UpdateRegistry(Register: Boolean); begin inherited UpdateRegistry(Register); if Register then AddKeys else RemoveKeys; end; initialization TIEHelperFactory.Create(ComServer, TIEHelper, Class_IEHelper, IEHelper, , ciMultiInstance, tmApartment); end.
代码很长，但是关键的是TIEHelper.SetSite方法以及TIEHelper.Invoke方法。在TIEHelper.SetSite方法中注意以下语句：
if Assigned(Sp)then
Sp.QueryService(IWebbrowserApp, IWebbrowser2, IE);
if Assigned(IE) then begin
IE.QueryInterface(IConnectionPointContainer, CPC);
CPC.FindConnectionPoint(DWEBbrowserEvents2, CP);
CP.Advise(Self, Cookie)
上面的语句作用是，首先获得IE的Webbrowser接口，然后寻找到连接点。并通过Advise方法建立COM自身与连接点的连接。
当连接建立成功后，IE在有事件引发后，会调用连接到自身的IDispatch接口对象的Invoke方法。不同的事件对应不同的DispID编码，我们可以在程序中判断DispID并做相应的处理。在上面的程序中，我们只处理了BeforeNavigate2 事件，处理函数是DoBeforeNavigate2，在该函数中，如果浏览的站点不是http://www.applevb.com/的话，程序会提示：你不可以浏览其它站点并强行转到http://www.applevb.com。
很多的软件，象“护花使者”以及“3721”一类的中文网址”都是利用上面的原理来实现对IE浏览器事件响应的，例如3721，当用户输入一个中文词并浏览时，COM组件可以在BeforeNavigate2 事件中编写代码访问服务器并转到正确的站点上去。