When WcmUsePojo activate() override method is called?

Ref: Adobe Experience Manager Help | Using an WCMUsePojo class to populate an Experience Manager Touch UI...

In that link, there are two java files which extends WcmUsePojo class and "activate" method is called in both files differently.

For HeroTextComponent, I think activate() is called when i press "tick" icon in dialog.

I am not sure how HtlDataSourceExample.activate() is called.