Hi Kimmo,
thanks you for the suggestion.
I have tried your suggestion but calling preventDefault() inside the overridden method didn't disable the navigation.
It seems that function "_checkCursorPosForNav(e, false)" is essential.
As I have said; with the code above the navigation is disabled, if the cursor is at the end of a text.
If the input field is empty or the cursor is at the beginning of the text, it still navigates to the next field.
I have also defined the "onsapnext" and "onsappreviuos" methodes for the parent object (Form) too...