检测 TWebBrowser 文档中的活动元素何时发生变化 [英] Detect when the active element in a TWebBrowser document changes
问题描述
是否有任何事件我可以挂钩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.
Is there any event I can hook into to detect when the active element on a web page changes? For example, when a the user focuses an edit box.
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.
I know I could check the active element in a timer, but I'd rather avoid this if possible.
推荐答案
这不是 - 完全 - 对您的问题的完整答案，但希望能帮助您完成大部分工作.
This isn't - quite - a complete answer to your q, but hopefully will get you most of the way there.
(对于通过类似问题到达这里的未来读者:
(For future readers who arrive here via a similar q:
假设您有一个用于自动化/Com 服务器(如 SHDocVw、MSHTML 或 MS Word)的类型库导入单元.有时，Delphi 的类型库导入器会为其生成的 Delphi TObject 后代包装器添加事件支持，例如 TWebBrowser、OnNavigateComplete 等的事件.其他时候它不能或不会生成 Delphi 包装器类，但您仍然可以附加通过多种方法之一连接到服务器对象事件，例如通过创建如下所示的 EventObject，它将服务器对象的事件与 Delphi 代码中的事件处理程序连接起来.
Suppose you have an type library import unit for an automation/Com server like SHDocVw, MSHTML or the one for MS Word. Sometimes, Delphi's type library importer adds event support to the Delphi TObject-descendant wrapper it generates, like the events for TWebBrowser, OnNavigateComplete, etc. Other times it can't or won't generate a Delphi wrapper class, but you can still attach to the server objects events by one of a number of methods, such as by creating an EventObject like the one below, which connects between a server object's events and an event-handler in your Delphi code.
处理接口事件基本上涉及定义一个实现 IDispatch 接口的 Delphi 类，然后将该接口连接到您想要通知其事件的 Ole 或 COM 对象.然后，当事件发生在接口后面"的 Ole/COM 中时，它会像调用 IDispatch 一样调用 IDispatch.您如何处理事件通知完全取决于您；下面的代码将它们传递给 TForm1 的方法.)
Handling interface events basically involves defining a Delphi class which implements an IDispatch interface and then connecting that interface to the Ole or COM object whose event(s) you want to be notified about. Then, when events occur in the Ole/COM "behind" the interface it calls your IDispatch the same way you call its one. What you do with the event notifications is entirely up to you; the code below passes them on to a method of TForm1. )
下面的 EventObject 与 TeamB 的 Deborah Pate 于 2003 年 11 月在 Borland NGs 上发布的事件密切相关(她的网站上有一个关于使用 Delphi 的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，因为它不限于处理任何特定 Ole/COM 对象的事件.
The EventObject below is closely based on a one posted in the Borland NGs in November 2003 by Deborah Pate of TeamB (she has a really good section on her website about automation using Delphi - http://www.djpate.freeserve.co.uk/Automation.htm). The object is quite generic, in that it's not limited to handling the events of any particular Ole/COM object.
// 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:aaad7htmlpostdata.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.如果您选中 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 INPUT 框时多次触发，每次都有不同的 Doc2.ActiveElement 值.我不确定为什么会这样，但这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 似乎确实提供了可靠的检查.
Note the comments in TForm1.AnEvent. If you check the cbSinkAll checkbox and run the code on a page with a number of INPUT boxes, you'll notice that AnEvent fires several times on entry to the same INPUT box, with a different value of Doc2.ActiveElement each time. I'm not sure why that is,but it does mean that comparing the current value of the Doc2.ActiveElement property with a previous value isn't effective to detect a change in focus on the Html page. However, comparing an attribute of the element, e.g. its Name or ID, does seem to provide a reliable check.
两个警告:
- 在 Deborah Pate 的原始代码中，她将之前的事件处理程序(如果有)保存到 OleVariant，以便以后可以恢复.
- 如果你想连续连接几个Html页面的事件，你应该释放中间的EventObject.
[从 MSHTML.Pas 中提取]
[Extract from MSHTML.Pas]
HTMLDocumentEvents = dispinterface
['{3050F260-98B5-11CF-BB82-00AA00BDCE0B}']
function onhelp: WordBool; dispid -2147418102;
[...]
procedure onbeforeeditfocus; dispid 1027;
end;
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