The Android app doesn't appear to give any kind of indication that a question has been closed, which I feel leads to poor UX. As an illustrative example, consider the (in)famous LOGO question:
As you can see, the left screenshot is the main question page, and it contains no
[closed] marker in the title. Not only that, but the "Add an answer" button is still available, and pressing it takes you to the text entry field as it normally does. It's only after you hit Submit or Preview that you're greeted with a message that says:
This question has been closed or locked; no new answers will be accepted.
So, potentially, if I stumbled on to a closed question that I felt I could contribute to, I could end up spending time typing up an answer only to have it rejected at the very end.
Ideally, I think the question title should reflect that it's been closed and the "Add an answer" button should be disabled or hidden. In addition to this, it would seem logical that duplicates should have the link to the original, so that landing on a dupe via the Android app doesn't leave you at a dead end (this is not currently the case, either). Showing the specific close reason (and other post notices) would be great as well, but I could see that being of slightly less concern since I can always tap on the question title to view it in a browser if I'm really curious about the "why".