This app was mentioned in 6 comments, with an average of 1.50 upvotes
this is more beginner friendly and more consistent. (in that it has plenty of tactics on every pattern and motif)
https://play.google.com/store/apps/details?id=net.lrstudios.android.chess_problems
and this one has real tactics from actual old master games, super interesting positions!
https://play.google.com/store/apps/details?id=vv.com.chesstactics
I actually got it, the daily puzzles must be having an effect.
Incidentally, I use Chess Tactics Pro for android.
Chess Tactics - Might only be in german. Very Solid App with 6 Daily Puzzles (Two easy, medium and hard each), as well as 200 Problems for offline use. You can download more Puzzles for like 99c but it does not bug you with it, at all.
https://play.google.com/store/apps/details?id=net.lrstudios.android.chess_problems&hl=de
I really like this free Android app Chess Tactics Pro
https://play.google.com/store/apps/details?id=net.lrstudios.android.chess_problems
Chess Tactics Pro is a good app.
https://play.google.com/store/apps/details?id=net.lrstudios.android.chess_problems&hl=tl
Good source of tactics are books and mobile apps.
Here is a good android chess tactics app.
https://play.google.com/store/apps/details?id=net.lrstudios.android.chess_problems&hl=tl