Disable the Instant Run option in Android Studio. Instructions are in the Android Studio Instant Run documentation. Instant Run tries to do hot swapping of your code; this causes the application class to be moved. To disable Instant Run Go to File –> Settings–> Build,Execution,Deployment –>Instant Run —> uncheck “Enable instant run”
Upgrade Android studio version to 3 or more. this bug is resolved. This was a bug on version 2.0 instant run and issues were reported check these links https://code.google.com/p/android/issues/detail?id=199884 https://code.google.com/p/android/issues/detail?id=195062 https://code.google.com/p/android/issues/detail?id=206698 https://code.google.com/p/android/issues/detail?id=209413 https://code.google.com/p/android/issues/detail?id=206627 thing to do would be to disable Instant Run entirely by Settings > Build, Execution, Deployment > Instant Run > Enable Instant … Read more
Update August 2019 In Android Studio 3.5 Instant Run was replaced with Apply Changes. And it works in different way: APK is not modified on the fly anymore but instead runtime instrumentation is used to redefine classes on the fly (more info). So since Android Studio 3.5 instant run settings are replaced with Deployment (Settings … Read more