RecyclerView adapter not working with groupie

karan dhillon :

I tried to add groupie adapter to my recycler view as shown in the code below. However when i run my application, i get a compiler error saying my reyclerview cannot be null (because of kotlin null safe feature). I cant figure out why this adapter is not working.

I know the problem is in the line :

recyclerview_newmessage.adapter = adapter

Here's the full code

class NewMessageActivity : AppCompatActivity() {

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

    supportActionBar?.title = "Select User"

    fetchUsers()
  }

  private fun fetchUsers() {
    val ref = FirebaseDatabase.getInstance().getReference("/users")
    ref.addListenerForSingleValueEvent(object: ValueEventListener {

        override fun onCancelled(p0: DatabaseError) {

        }

        override fun onDataChange(p0: DataSnapshot) {
            val adapter = GroupAdapter<ViewHolder>()
            p0.children.forEach {
                Log.d("NewMessage", it.toString())
                val user = it.getValue(User::class.java)

                if (user != null) {
                    adapter.add(UserItem(user))
                }
            }

            recyclerview_newmessage.adapter = adapter
        }

    })
  }
}

class UserItem(val user: User): Item<ViewHolder>() {

  override fun bind(viewHolder: ViewHolder, position: Int) {
    viewHolder.itemView.username_textview_new_message.text = user.username
  }

  override fun getLayout(): Int {
    return R.layout.user_row_new_message
  }
}

The final result show display the rows in the recycler view with the usernames that are in my firebase database.

Amninder Singh :

If you define the recycler view in the xml file then you need to add it.

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContentView(R.layout.ref_xml_file) . // add this line
    supportActionBar?.title = "Select User"

    fetchUsers()
  }

if not define into the xml file.

override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        var recyclerview_newmessage = RecyclerView(this)
        setContentView(recyclerview_newmessage) . // add this line
        supportActionBar?.title = "Select User"

        fetchUsers()
      }