It happens from time to time in Android Studio 3. This are steps to try to resolve this issue:
- invalidate cache and restart studio;
- choose different emulator from
- refresh layout by clicking on eye icon at the top of layout designer view.
The best fix that worked for me was to minimize all the tools on the bottom, i.e Run, Logcat, TODO, Terminal, Build and more … Then the zoom buttons start working. Even you open the tools back again, the zoom will keep working.
My complete answer is here:
I am having the same problem on Androd Studio 3.3.1. The solution is a bit silly.
Every time the zoom stops working I drag the bottom area (where you have the logcat/build/run) all the way to the top, so it hides your xml. Then drag it back down.
The zoom will start working again.