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 := to dps.cArgs - do
pDispIds^[i] := dps.cArgs - - i;
if (dps.cNamedArgs <= ) then Exit;
for i := to dps.cNamedArgs - 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 := ;
bHasParams := (dps.cArgs > );
if (bHasParams) then
begin
iDispIdsSize := dps.cArgs * SizeOf(TDispId);
GetMem(pDispIds, iDispIdsSize);
end;
try
if (bHasParams) then BuildPositionalDispIds(pDispIds, dps);
case DispId of
:
begin
DoStatusTextChange(dps.rgvarg^[pDispIds^[]].bstrval);
Result := S_OK;
end;
:
begin
DoProgressChange(dps.rgvarg^[pDispIds^[]].lval, dps.rgvarg^[pDispIds^[]].lval);
Result := S_OK;
end;
:
begin
DoCommandStateChange(dps.rgvarg^[pDispIds^[]].lval, dps.rgvarg^[pDispIds^[]].vbool);
Result := S_OK;
end;
:
begin
DoDownloadBegin();
Result := S_OK;
end;
:
begin
DoDownloadComplete();
Result := S_OK;
end;
:
begin
DoTitleChange(dps.rgvarg^[pDispIds^[]].bstrval);
Result := S_OK;
end;
:
begin
DoPrtype
POleVariant = ^OleVariant;
var
dps: TDispParams absolute Params;
bHasParams: boolean;
pDispIds: PDispIdList;
iDispIdsSize: integer;
begin
Result := DISP_E_MEMBERNOTFOUND;
pDispIds := nil;
iDispIdsSize := ;
bHasParams := (dps.cArgs > );
if (bHasParams) then
begin
iDispIdsSize := dps.cArgs * SizeOf(TDispId);
GetMem(pDispIds, iDispIdsSize);
end;
try
if (bHasParams) then BuildPositionalDispIds(pDispIds, dps);
case DispId of
:
begin
DoStatusTextChange(dps.rgvarg^[pDispIds^[]].bstrval);
Result := S_OK;
end;
:
begin
DoProgressChange(dps.rgvarg^[pDispIds^[]].lval, dps.rgvarg^[pDispIds^[]].lval);
Result := S_OK;
end;
:
begin
DoCommandStateChange(dps.rgvarg^[pDispIds^[]].lval, dps.rgvarg^[pDispIds^[]].vbool);
Result := S_OK;
end;
:
begin
DoDownloadBegin();
Result := S_OK;
end;
:
begin
DoDownloadComplete();
Result := S_OK;
end;
:
begin
DoTitleChange(dps.rgvarg^[pDispIds^[]].bstrval);
Result := S_OK;
end;
:
begin
DoPropertyChange(dps.rgvarg^[pDispIds^[]].bstrval);
Result := S_OK;
end;
:
begin
DoBeforeNavigate2(IDispatch(dps.rgvarg^[pDispIds^[]].dispval), POleVariant(dps.rgvarg^[pDispIds^[]].pvarval)^, POleVariant(dps.rgvarg^[pDispIds^[]].pvarval)^, POleVariant(dps.rgvarg^[pDispIds^[]].pvarval)^, POleVariant(dps.rgvarg^[pDispIds^[]].pvarval)^, POleVariant(dps.rgvarg^[pDispIds^[]].pvarval)^, dps.rgvarg^[pDispIds^[]].pbool^);
Result := S_OK;
end;
:
begin
DoNewWindow2(IDispatch(dps.rgvarg^[pDispIds^[]].pdispval^), dps.rgvarg^[pDispIds^[]].pbool^);
Result := S_OK;
end;
:
begin
DoNavigateComplete2(IDispatch(dps.rgvarg^[pDispIds^[]].dispval), POleVariant(dps.rgvarg^[pDispIds^[]].pvarval)^);
Result := S_OK;
end;
:
begin
DoDocumentComplete(IDispatch(dps.rgvarg^[pDispIds^[]].dispval), POleVariant(dps.rgvarg^[pDispIds^[]].pvarval)^);
Result := S_OK;
end;
:
begin
DoOnQuit();
Result := S_OK;
end;
:
begin
DoOnVisible(dps.rgvarg^[pDispIds^[]].vbool);
Result := S_OK;
end;
:
begin
DoOnToolBar(dps.rgvarg^[pDispIds^[]].vbool);
Result := S_OK;
end;
:
begin
DoOnMenuBar(dps.rgvarg^[pDispIds^[]].vbool);
Result := S_OK;
end;
:
begin
DoOnStatusBar(dps.rgvarg^[pDispIds^[]].vbool);
Result := S_OK;
end;
:
begin
DoOnFullScreen(dps.rgvarg^[pDispIds^[]].vbool);
Result := S_OK;
end;
:
begin
DoOnTheaterMode(dps.rgvarg^[pDispIds^[]].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 := ;
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。