0_UserActivity.kt

class UserDetailActivity : Activity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

        val userId = intent.getStringExtra(INTENT_USER_ID)
                ?: throw IllegalStateException("field $INTENT_USER_ID missing in Intent")
    }

    companion object {

        private val INTENT_USER_ID = "user_id"

        fun newIntent(context: Context, user: User): Intent {
            val intent = Intent(context, UserDetailActivity::class.java)
            intent.putExtra(INTENT_USER_ID, user.id)
            return intent
        }
    }
}

1_OtherActivity.kt

class OtherActivity : Activity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        //...
        userlist.clickListener { user ->
            val intent = UserDetailActivity.newIntent(this, user)
            startActivity(intent)
        }
    }
}