FATAL EXCEPTION: main Process: com.example.utente.lets_appv0, PID: 8477 java.lang.IllegalArgumentException: Capacity: -8

at least provide stacktrace

emmm yes.... is it forbidden to make question for android?

Again, I would just reference this slack guidelines:

Please remember this is a Slack team for Kotlin. If you have generic questions that are about a technology (which may or may not be used with Kotlin), maybe it’s better to use another forum, such as StackOverflow.

sorry i'll just stop. Thank you anyway

Just recommendation, even if you ask this question somewhere else, share your error message stacktrace, maybe logs, maybe provide some code sample that could help someone to understand your case and maybe help you. Because there is no information that can be helpful. I just can say you have this

IllegalArgumentException

because passed value -8 to some method, I suppose capacitiy cannot be less than 0 or 1