Fit Contributor MESG_TYPE_SESSION does not show up in Fit file

You have to create all FIT fields, even SESSION fields, before you start recording.

I changed the order of creating the fields:

function onSelect() {
   	if (Toybox has :ActivityRecording) { 
		if ((session == null) || (session.isRecording() == false)) {
   	        // Start session:
	       	session = createSession();  // Own function to create session
		    if (session != null) {
		        createFields();         // Own function to create fields
		   		session.start();
		    }
	    }
	    else {
            saveAvgSessionData();       // Own function to save 
            App.stopRecording(true);    // Own funciton to stop recording and remove session
	    }
   	}
   	return true;
}

function createFields() {
	if (session != null && !session.isRecording()){
	    // ... Some recording fit fields: ...
		fieldStrideLength = session.createField("stride_length", 1, FitContributor.DATA_TYPE_FLOAT, { :mesgType=>FitContributor.MESG_TYPE_RECORD, :units=>"m" });
		// ... Some session fit fields: ...
		fieldStrideLengthAvg = session.createField("stride_length_avg", 3, FitContributor.DATA_TYPE_FLOAT, { :mesgType=>FitContributor.MESG_TYPE_SESSION, :units=>"m" });
	}
}

// Stride length is recorded every second...

function saveAvgSessionData() {
    // ... Calcutlate avgStrideLength ...
	fieldStrideLengthAvg.setData(avgStrideLength);
}

However, I still cannot see the average stride length data in my fit files... :(

Try calling saveAvgSessionData() every second (or as often as you write RECORD data). It's counter-intuitive, but setData() only queues the *next* value to be written, and you may be calling it too late here.

(You can see an example of this in the SDK's MoxyField sample, although it's a data field and not a device app.)

I just tried that. Did also not work :/

Am I correct that the session data collected here should be added to the fit file at the end where it says "Data,13,session,timestamp ..."?

I am getting annoyed by this problem... Is there any other reason why it should not show up in the fit file?

I have just checked that if I replace MESG_TYPE_SESSION by MESG_TYPE_RECORD, then it is correctly recorded in the fit file as record data. Hence, there must be some issue with the Session. Could it be that I am leaving the session in a strange way that does not allow saving the session data correctly?

When you are at the end, do you do both session.stop() and session.save()?

What does App.stopRecording(true) do?

Does it call ActivityRecording.Session.save()?

Yes. App.stopRecording(save) stops the session and saves it if save is set true:

class App extends Application.AppBase {

    // ...
    
    function stopRecording(save) {
		if( Toybox has :ActivityRecording ) {
            if ((session != null) && session.isRecording()) {
		       	session.stop();
		       	if (save) {
			   		session.save();
			   	}
			   	else {
			   		session.discard();
			   	}
			    session = null;
		    }
        }
    } 
    
}

Make sure to do the session.stop() before the session.save()

is looks like if isRecording is false (the session is stopped) you won't do the save.

This was the issue! :D Yesterday, I have just added an extra stop for the menu selection option which calls session.stop() before calling App.stopRecording(true). 

Thanks!

.. what a stupid mistake ..