FitContibution: Call setData for unchanged data?

You're right, the line of the documentation that you quoted is unclear, and it doesn't really reflect how some of the recording samples in the SDK are coded.

JensDuttke said:

Now I'm wondering if I should just call `setData` and let this method take care of whether the value is changed before writing it to the FIT file, if I should take care not to write unchanged data, or even if Garmin creates an entry every second even when `setData` has not been called.

Just call setData() unconditionally, IMO. With one exception (*), setData() never causes data to be written, it sets the next value to be written, and the firmware decides when to write.

(*) The sort of exception to this rule is that before you call setData() for the first time, no data will be written. Once you call setData() for the first time, that causes data to be written for the first time. e.g. If you call setData() for the first time five minutes into the activity, then the FIT graph will be blank until that point.

Obviously I don't know your code, but it seems simpler to just call setData() unconditionally, as opposed to storing the previous value and checking to see if the current value differs.

Another thing to note is that if you are writing session or lap data, you have to call setData() *before* the lap is triggered or the session ends. For example, it's too late to write lap data in onTimerLap().

The usual way to do this is to call setData() lap data and session data *all the time* (e.g. once per second), even though the actual values will be written far less frequently. (You can see this is the SDK MoxyField sample app, which has FIT recording.)

(However, another way to handle writing session data is to call setData() in onTimerStop(), since the user has to stop an activity before saving it.)