Issues with Initializing DataField and Displaying Values in the App

I am currently developing a data field app for a Garmin device using the WatchUi.DataField class. My goal is to display values such as heart rate, altitude, and other sensor data. While I can successfully view these values using the WatchUi.View class, I encounter issues when attempting to use the DataField class. Specifically, I am unable to see the values.

I chose to use DataField to create a custom data field for easier access and management of the data for later usage. How can I solve this problem so that I can see the values and save it in the custom data fields?  Thank you in advance.