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{{KBKI}}
__NOTOC__
__NOEDITSECTION__
{{KnowledgeBase
|id=KIS000588
|platform=S60 3rd Edition, S60 3rd Edition, FP1
|devices=
|category=Symbian C++
|subcategory=Base & System, Application Framework
|creationdate=February 22, 2007 (Last updated: November 1, 2007)
|keywords=
}}

==Description==
When letting the system find and launch the handler application for a file with a recognized MIME type, the handler receives a call to its <tt>CAknDocument::OpenFileL()</tt> implementation. However, if the handler application is already running in the background, the <tt>OpenFileL()</tt> call for the document class is not received.


==Solution==
In addition to <tt>CEikDocument::OpenFileL()</tt>, data handler applications in S60 must also provide an implementation for <tt>CAknAppUi::OpenFileL()</tt>.

A common way to solve this is to redirect the call to document class in <tt>CAknAppUi::OpenFileL()</tt>:

  void CHandlerAppUi::OpenFileL( const TDesC& aFileName )
    {
    CHandlerDocument* doc = static_cast<CHandlerDocument*>( Document() );
    doc->OpenFileL( ETrue, aFileName, iEikonEnv->FsSession() );
    }


If the handler application is running in the background, the calling application must call <tt>TApaTask::SwitchOpenFile()</tt>:

  TBool CCallingAppUi::RefreshDocumentFileL( const TUid& aUid, 
                                             const TDesC& aFileName )
    {
    TApaTaskList taskList( iCoeEnv->WsSession() );
    // Find handler application by its UID
    TApaTask task = ( taskList.FindApp( aUid ) ); 
    if ( task.Exists() )
      {
      // Calls CAknAppUi::OpenFileL(), requires SwEvent capability
      User::LeaveIfError( task.SwitchOpenFile( aFileName ) );
      return ETrue;
      }
    return EFalse;
    }


If a file is launched from the S60 Web Browser or File Manager, a different approach is required as there will be no call to <tt>SwitchOpenFile()</tt>. The handler application itself can check for other instances of itself already running in the background. By default, the application framework brings the old instance to foreground, and terminates the new one. It is possible to change this behaviour by overriding <tt>PreDocConstructL()</tt> function from <tt>CAknApplication</tt> class:

  void CHandlerApplication::PreDocConstructL()
    {
    CEikonEnv* env = CEikonEnv::Static();
    
    // Check that this app is started as stand-alone
    if (!env->StartedAsServerApp() && !env->EikAppUi())
      {
      RWsSession& ws = env->WsSession();
      const TInt myWgId = env->RootWin().Identifier();
      TInt wgId = 0;  
      TUid uid(AppDllUid());
    
      // Look for another instance of this app
      while (wgId >= 0)
        {
        if (wgId && wgId != myWgId) // Another instance found -> close it
          {
          TApaTask other(ws);
          other.SetWgId(wgId);
          other.EndTask();          // Requires SwEvent capability
          }
        CApaWindowGroupName::FindByAppUid(uid, ws, wgId);
        }
      }
    
    // call PreDocConstructL from base class
    CEikApplication::PreDocConstructL();
    }
	
	
Note that above code works only for stand-alone (non-embedded) handler applications, and required '''SwEvent''' capability.<br>

'''See also:'''

[http://wiki.forum.nokia.com/index.php/TSS000419_-_S60_MIME_recognizers_and_opening_files_for_editing TSS000419 - S60 MIME recognizers and opening files for editing] <br>
[http://www.forum.nokia.com/info/sw.nokia.com/id/3e6c5f1f-1fb3-4c04-96ad-40979c7f2665/S60_Platform_Document_Handler_Example_v1_0_en.zip.html S60 Platform: Document Handler Example] and<br>
[http://www.forum.nokia.com/info/sw.nokia.com/id/6eb5fdd0-5ae7-4bfa-a927-8657707cfd55/S60_Platform_Document_Handler_API_Developers_Guide.html  S60 Platform: Document Handler API Developer’s Guide] available for download at [http://www.forum.nokia.com Forum Nokia]

[[Category:Known Issue]][[Category:Symbian C++]][[Category:Base/System]] [[Category:S60 3rd Edition]] [[Category:S60 3rd Edition, Feature Pack 1]]