FitContributor error message

When start my app and after take GPS signal i have !Iconerror message.

This becouse i want record data in Fit file using Fitcontributor.

This is my code in InputDelegate:

using Toybox.FitContributor as Fit;

var session = null;

var heartRateFF = null;
var AltitudeFF = null;

if( ( session == null ) || ( session.isRecording() == false ) ) {
    session = ActivityRecording.createSession({:name=>"Generic", :sport=>ActivityRecording.SPORT_CYCLING});

    heartRateFF = session.createField("Heart Rate", 0, Fit.DATA_TYPE_UINT8, {:mesgType => Fit.MESG_TYPE_RECORD, :units => "bpm"});
    AltitudeFF = session.createField("Altitude", 1, Fit.DATA_TYPE_UINT8, {:mesgType => Fit.MESG_TYPE_RECORD, :units => "mt"});

    session.start();
     WatchUi.requestUpdate();
}
else if( ( session != null ) && session.isRecording() ) {
session.stop();
session.save();
session = null;
WatchUi.requestUpdate();
}
}

this is code in InputView on Update(c):

activityInfoX = Activity.getActivityInfo();

if (activityInfoX != null) {
    infoalt = activityInfoX.altitude.format( "%.0d" );
    hrrate = activityInfoX.currentHeartRate != null ? activityInfoX.currentHeartRate : 0;

   heartRateFF.setData(hrrate);
   AltitudeFF.setData(infoalt);

}

i dont understand my mistake ?

can be that i must declare use of using Toybox.FitContributor as Fit; also in InputView module ?

thanks