Where To Handle Cab Actions Of A List Item That Are Common With Detail?

lets say I have master/detail pattern using fragments, so as usual, the detail fragment would be inside new activity on a phone and on a tablet it would be inside the previous acti

Solution 1:

where should I have that sharing code? I want to avoid duplicates

Taking a guess that "that sharing code" is your ACTION_SEND invocation, since that is only a half-dozen lines of code or so, tuck that in a static method somewhere that can be accessed by your detail fragment and by the activity that is hosting the list on smaller screens.