Sometimes this scenario occurs when developing. I would make a change in my source code, hit save all and then run but the change wouldn't be apparently not reflected in the app -(I'm using a device for testing). I can even uninstall the app on my device, and hit run again and the newly installed app still hasn't reflected the change in the source code. When this happens I have to edit the source, hit run and maybe then a new version with the changes I expected will be on the device.
I also tried the solution here, but it doesn't seem to work often.
I've got the same problem. This thread popped up first when I've searched for it. Solved it (hoping so) by not using the Instant Run feature. Might not be the best solution but it works for now.
Just go to "File -> Settings -> Build, Execution, Deployement -> Instant Run" and just disable it. With this Android Studio builds from scratch each time but it's better than not building it right.
Mini rant: Almost each version of Android Studio comes with an annoying bug. They're about to release the version 2 but its beta is still buggy. I hope they stabilize the IDE in the near future.
I'm using Android Studio 2.1 and I still have the same issue. The only solution was to disabled the instant run :(
Have this problem even with "Instant Run" disabled, quite annoying!!! AS 2.1.2. 'Clean' helps ...
If anyone else is also looking for it, on OS X you can find it under
File -> Preferences -> Build, Execution, Deployment
I think Disabling Instant run is not a good solution. It has so many benefits and just one bug.
I'm using the Android Studio 3.2 Canary 13 with Instant Run disabled and this issue still persist.