TWebBrowser: Determine when a page with Frames is completed

浏览数：35 / 时间：2015年06月09日

TWebBrowser: Determine when a page with Frames is completed

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Question:

If I load a web page with TWebBrowser that contains frames then the OnDocumentComplete() is hit for each frame. How can I recognize that the page is completely loaded (no more frames missing)?

Answer:

Indeed, in case of multiple frames, OnDocumentComplete gets fired multiple times. Not every frame fires this event, but each frame that fires a DownloadBegin event will fire a corresponding DocumentComplete event.

How can the ‘real completion‘ be recognized?

The OnDocumentComplete event sends parameter pDisp: IDispatch, which is the IDispatch of the frame (shdocvw) for which DocumentComplete is fired. The top-level frame fires the DocumentComplete in the end.

So, to check if a page is done downloading, you need to check if pDisp is same as the IDispatch of the WebBrowser control.

That‘s what the code below demonstrates.

procedure TForm1.WebBrowser1DocumentComplete(Sender: TObject;
               const pDisp: IDispatch; var URL: OLEvariant);
var
  CurWebrowser : IWebBrowser;
  TopWebBrowser: IWebBrowser;
  Document     : OLEvariant;
  WindowName   : string;
begin { TForm1.WebBrowser1DocumentComplete }
  CurWebrowser := pDisp as IWebBrowser; 
  TopWebBrowser := (Sender as TWebBrowser).DefaultInterface; 
  if CurWebrowser=TopWebBrowser then 
  begin
    ShowMessage(‘Document is complete.‘) 
  end
  else 
  begin 
    Document := CurWebrowser.Document; 
    WindowName := Document.ParentWindow.Name; 
    ShowMessage(‘Frame ‘ + WindowName + ‘ is loaded.‘)
  end;
end;