Android Studio: Installation failed since APK was not signed

Question

I am attempting to run my app in an emulator and have been receiving the following error:

Installation failed since the APK was either not signed, or

Answer 1

I had this same problem occur last night. Running in debug, in my case the app had previously been installed from weeks ago, and I had deleted it, but I was still getting the error and couldn't install it again. I was able to resolve it by going into the AVD manager and wiping user data from there. After that installation and debugging went fine.