是否有任何可以挂钩的事件来检测网页上的活动元素何时发生变化?例如,当用户聚焦编辑框时。
我知道我可以检查计时器中的活动元素,但如果可能的话我宁愿避免这种情况。
答案 0 :(得分:10)
这不是 - 完全 - 你的q的完整答案,但希望能在那里得到你的大部分。
(对于通过类似问题来到这里的未来读者:
假设您有自动/ Com服务器的类型库导入单元,如SHDocVw,MSHTML或MS Word。有时,Delphi的类型库导入器为它生成的Delphi TObject-descendant包装器添加事件支持,比如TWebBrowser,OnNavigateComplete等的事件。有时它不能或不会生成Delphi包装类,但你仍然可以附加通过多种方法之一对服务器对象事件,例如通过创建如下所示的EventObject,它连接服务器对象的事件和Delphi代码中的事件处理程序。
处理接口事件主要涉及定义Delphi类,该类实现IDispatch接口,然后将该接口连接到要通知其事件的Ole或COM对象。然后,当Ole / COM“后面”接口发生事件时,它会调用您的IDispatch,就像调用它一样。您对事件通知的处理完全取决于您;下面的代码将它们传递给TForm1的方法。 )
下面的EventObject紧密基于2003年11月Borland NGs在TeamB的Deborah Pate发布的一个(她在她的网站上有一个关于使用Delphi进行自动化的非常好的部分 - http://www.djpate.freeserve.co.uk/Automation.htm)。该对象非常通用,因为它不仅限于处理任何特定Ole / COM对象的事件。
// The following code is intended to illustrate methods of detecting that the
// active element in an Html page has changed. See the comments in the AnEvent
// procedure about how exactly to detect such a change.
//
// The code also illustrates how to handle a single event, e.g. onbeforeeditfocus
// of an Events objects such as HtmlDocumentEvents or HtmlDocumentEvents2 (see MSHTML.Pas)
// or all the events the events interface contains.
type
TInvokeEvent = procedure(Sender : TObject; DispIP : Integer) of Object;
TEventObject = class(TInterfacedObject, IDispatch)
private
FOnEvent: TInvokeEvent;
FSinkAllEvents : Boolean;
protected
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;
public
constructor Create(const AnEvent : TInvokeEvent; SinkAll : Boolean);
property OnEvent: TInvokeEvent read FOnEvent write FOnEvent;
property SinkAllEvents: Boolean read FSinkAllEvents;
end;
type
TForm1 = class(TForm)
[ ... ]
private
{ Private declarations }
procedure AnEvent(Sender : TObject; DispID : Integer);
procedure AnotherEvent(Sender : TObject; DispID : Integer);
public
{ Public declarations }
Doc : IHtmlDocument3;
DocEvent,
DocEvent2: OleVariant;
Cookie : Longint;
CPC : IConnectionPointContainer;
Sink : IConnectionPoint;
PrvActiveElement : IHTMLElement;
Events : Integer;
end;
var
Form1: TForm1;
implementation
{$R *.dfm}
constructor TEventObject.Create(const AnEvent: TInvokeEvent; SinkAll : Boolean);
begin
inherited Create;
FOnEvent := AnEvent;
FSinkAllEvents := SinkAll;
end;
function TEventObject.GetIDsOfNames(const IID: TGUID; Names: Pointer;
NameCount, LocaleID: Integer; DispIDs: Pointer): HResult;
begin
Result := E_NOTIMPL;
end;
function TEventObject.GetTypeInfo(Index, LocaleID: Integer;
out TypeInfo): HResult;
begin
Result := E_NOTIMPL;
end;
function TEventObject.GetTypeInfoCount(out Count: Integer): HResult;
begin
Result := E_NOTIMPL;
end;
function TEventObject.Invoke(DispID: Integer; const IID: TGUID;
LocaleID: Integer; Flags: Word; var Params; VarResult, ExcepInfo,
ArgErr: Pointer): HResult;
begin
if SinkAllEvents then begin
if Assigned(FOnEvent) then
FOnEvent(Self, DispID);
Result := S_OK;
end
else begin
if (Dispid = DISPID_VALUE) then begin
if Assigned(FOnEvent) then
FOnEvent(Self, DispID);
Result := S_OK;
end
else Result := E_NOTIMPL;
end;
end;
procedure TForm1.AnEvent(Sender : TObject; DispID : Integer);
var
Doc2 : IHTMLDocument2;
E : IHTMLElement;
begin
Inc(Events);
Doc.QueryInterface(IHTMLDocument2, Doc2);
E := Doc2.activeElement;
// NB: When an <INPUT> text edit is receiving focus, the following code is triggered twice
// or more with different values of Pointer(Doc2.activeElement). So, "(E <> PrvActiveElement)"
// doesn't seem a very effective test that the active element has changed. However,
// testing E's Name, ID, etc should provide a useful test.
if (E <> Nil) and (E <> PrvActiveElement) and E.isTextEdit then begin
if PrvActiveElement <> Nil then
PrvActiveElement := E;
Caption := Format('Something happened: Element Tagname: %s, Name: %s, %d, %d, %p',
[E.TagName, E.GetAttribute('Name', 0), DispID, Events, Pointer(Doc2.activeElement)]);
end;
end;
procedure TForm1.AnotherEvent(Sender : TObject; DispID : Integer);
begin
Caption := Format('Something else happened: %d', [DispID]);
end;
procedure TForm1.FormCreate(Sender: TObject);
begin
Memo1.Lines.LoadFromFile('D:\aaad7\html\postdata.htm');
end;
procedure TForm1.btnLoadClick(Sender: TObject);
var
V : OleVariant;
Doc2 : IHtmlDocument2;
begin
WebBrowser1.Navigate('about:blank');
Doc := WebBrowser1.Document as IHTMLDocument3;
Doc.QueryInterface(IHTMLDocument2, Doc2);
V := VarArrayCreate([0, 0], varVariant);
V[0] := Memo1.Lines.Text;
try
Doc2.Write(PSafeArray(TVarData(v).VArray));
finally
Doc2.Close;
end;
DocEvent := TEventObject.Create(Self.AnEvent, cbSinkAll.Checked) as IDispatch;
if cbsinkAll.Checked then begin
CPC := Doc2 as IConnectionPointContainer;
Assert(CPC <> Nil);
OleCheck(CPC.FindConnectionPoint(HTMLDocumentEvents, Sink));
OleCheck((Sink as IConnectionPoint).Advise(DocEvent, Cookie));
end
else
Doc.onbeforeeditfocus := DocEvent;
end;
注意TForm1.AnEvent中的注释。如果选中cbSinkAll复选框 并在具有多个INPUT框的页面上运行代码,您会注意到AnEvent在进入相同的 INPUT框时会多次触发,每次都有不同的Doc2.ActiveElement值。我不确定为什么会这样,但它确实意味着比较当前 具有先前值的Doc2.ActiveElement属性的值无法有效检测更改 专注于Html页面。但是,比较元素的属性,例如,它的名称或ID似乎提供了可靠的检查。
两个警告:
[从MSHTML.Pas中提取]
HTMLDocumentEvents = dispinterface
['{3050F260-98B5-11CF-BB82-00AA00BDCE0B}']
function onhelp: WordBool; dispid -2147418102;
[...]
procedure onbeforeeditfocus; dispid 1027;
end;