I can't reach any class member from a nested class in Kotlin

Question

I want to access a member of the MainFragment class from PersonAdapter class but none of them are available. I tried making both the classes and the members public and private also but so far nothing worked. I guess I'm missing something obvious but I just can't figure it out.

class MainFragment : Fragment() {     lateinit var personAdapter: PersonAdapter     lateinit var personListener: OnPersonSelected     private var realm: Realm by Delegates.notNull()     lateinit var realmListener: RealmChangeListener<Realm>      override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {         val v = inflater.inflate(R.layout.fragment_main, container, false)         return v     }      class PersonAdapter() : RecyclerView.Adapter<ViewHolder>() {         var localPersonList = personList          override fun onBindViewHolder(holder: ViewHolder, position: Int) {             holder.bindItems(localPersonList[position])              holder.itemView.setOnClickListener {                 Toast.makeText(context, "click", Toast.LENGTH_SHORT).show()                 //I want to reach personListener from here             }         }          override fun onCreateViewHolder(parent: ViewGroup?, viewType: Int): ViewHolder {             val v = LayoutInflater.from(parent!!.context).inflate(R.layout.person_list_item, parent, false)             return ViewHolder(v)         }     }} 

Answer 1

In Kotlin, nested classes cannot access the outer class instance by default, just like nested static classes can't in Java.

To do that, add the inner modifier to the nested class:

class MainFragment : Fragment() {     // ...      inner class PersonAdapter() : RecyclerView.Adapter<ViewHolder>() {         // ...     } } 

Note that an inner class holds a reference to its containing class instance, which may affect the lifetime of the latter and potentially lead to a memory leak if the inner class instance is stored globally.

See: Nested classes in the language reference