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ID	KIS000588	Creation date	February 22, 2007 (Last updated: November 1, 2007)
Platform	S60 3rd Edition, S60 3rd Edition, FP1	Devices
Category	Symbian C++	Subcategory	Base & System, Application Framework

Keywords (APIs, classes, methods, functions):

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 CAknDocument::OpenFileL() implementation. However, if the handler application is already running in the background, the OpenFileL() call for the document class is not received.

Solution

In addition to CEikDocument::OpenFileL(), data handler applications in S60 must also provide an implementation for CAknAppUi::OpenFileL().

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

 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 TApaTask::SwitchOpenFile():

 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 SwitchOpenFile(). 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 PreDocConstructL() function from CAknApplication 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.

See also:

TSS000419 - S60 MIME recognizers and opening files for editing
S60 Platform: Document Handler Example and
S60 Platform: Document Handler API Developer’s Guide available for download at Forum Nokia