重新启动“活动”之前，我无法检索Firebase数据库数据

Question

我正在创建一个屏幕，需要从Firebase实时数据库检索数据并将其显示在recyclerview中。如果我尝试打开活动，则不会加载或显示数据，但是如果我再次打开活动，则数据将正确显示。我相信我也无法写入数据库

活动：

        class SelectCollaborators : AppCompatActivity() {

    private val listaIdsCollaboratorsSelecionar = ArrayList<Collaborator>()
    private var collaboratorsRef: DatabaseReference = FirebaseDatabase.getInstance().reference
            .child("collaborators")
            .child(UsuarioFirebase.getIdentificadorUsuario())//get current user id

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_selecionar_membros)

        Log.i("selecionar","REF:" + collaboratorsRef.toString())

        iniciarToolbar()

        iniciarRecyclerView()

        listarCollaboratorsParaSelecionar()

        fabSelecionarMembros.setOnClickListener {
            startActivity(Intent(applicationContext, DetalhesGrupoActivity::class.java))
        }

        Toast.makeText(applicationContext,"onCreate",Toast.LENGTH_SHORT).show()

    }

    private fun iniciarRecyclerView(){
        recyclerSelecionarMembros.setLayoutManager(LinearLayoutManager(applicationContext))
        recyclerSelecionarMembros.setHasFixedSize(true)


    }

    private fun listarCollaboratorsParaSelecionar() {
        listaIdsCollaboratorsSelecionar.clear()
        val postListener = object : ValueEventListener {
            override fun onDataChange(dataSnapshot: DataSnapshot) {
                // Get Post object and use the values to update the
                for(ds in dataSnapshot.children){
                    val collaborator = ds.getValue(Collaborators::class.java)
                    //reperarDadosUsuarioAtualizado(collaborator!!.id)
                    listaIdsCollaboratorsSelecionar.add(collaborator!!)
                    Log.i("selecionar","NOME:" + collaborator.nomeExibicao)
                }
                recyclerSelecionarMembros.adapter = AdapterSelecionarMembros(listaIdsCollaboratorsSelecionar,applicationContext)
                recyclerSelecionarMembros.adapter!!.notifyDataSetChanged()
            }

            override fun onCancelled(databaseError: DatabaseError) {
                // Getting Post failed, log a message
                Log.i("selecionar", "loadPost:onCancelled", databaseError.toException())
                // ...
            }
        }
        collaboratorsRef.addValueEventListener(postListener)
    }

    private fun iniciarToolbar(){
        val toolbar:Toolbar = findViewById(R.id.toolbarSelecionarMembros)
        setSupportActionBar(toolbar)
        getSupportActionBar()!!.setDisplayHomeAsUpEnabled(true)
        supportActionBar!!.title = resources.getString(R.string.titleActivityAdicionarMembros)
    }

    override fun onCreateOptionsMenu(menu: Menu?): Boolean {
        val menuInflater = menuInflater
        menuInflater.inflate(R.menu.menu_pesquisa, menu)
        return super.onCreateOptionsMenu(menu)
    }

    override fun onOptionsItemSelected(item: MenuItem): Boolean {
        return super.onOptionsItemSelected(item)
    }

    override fun onStart() {
        super.onStart()
        Toast.makeText(applicationContext,"onStart",Toast.LENGTH_SHORT).show()
    }

    override fun onResume() {
        super.onResume()
        Toast.makeText(applicationContext,"onResume",Toast.LENGTH_SHORT).show()

    }
}

数据库：

    "collaborators" : {
        "5P6DzPIEuiSKU5UYGo03AwSMTED3" : {
          "HeGEtXVmf0btmlg4CGO2s5YZtdQ2" : {
            "caminhoFoto" : "https://firebasestorage.googleapis.com/v0...",
            "id" : "HeGEtXVmf0btmlg4CGO2s5YZtdQ2",
            "nomeExibicao" : "Jane Doe"
            "nomePesquisa" : "JANE DOE"
          },
          "nKTlIyaDc3O3gxNpsz8hwUrbGq53" : {
            "caminhoFoto" : "https://firebasestorage.googleapis.com/...",
            "id" : "nKTlIyaDc3O3gxNpsz8hwUrbGq53",
            "nomeExibicao" : "John Doe",
            "nomePesquisa" : "JOHN DOE"
          }
        },

适配器：（目前仅显示图像，以后将添加其他项目）

class AdapterSelecionarMembros(private val listaCollaborators:List<Collaborators>, private val context: Context) : RecyclerView.Adapter<AdapterSelecionarMembros.ViewHolder>() {

override fun onCreateViewHolder(viewGroup: ViewGroup, i: Int): ViewHolder {
    val itemView = LayoutInflater.from(viewGroup.context)
            .inflate(R.layout.item_selecionar_membros, viewGroup, false)
    return ViewHolder(itemView)
}

override fun onBindViewHolder(holder: ViewHolder, position: Int) {
    val membroId = listaCollaborators[position]
                    Glide.with(context)
                            .load(membroId.caminhoFoto)
                            .into(holder.foto)
}

override fun getItemCount(): Int {
    return listaCollaborators.size
}

inner class ViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {
    val foto:RoundedImageView = itemView.findViewById(R.id.imageSelecionarMembro)
    val nome:TextView = itemView.findViewById(R.id.textNomeMembroListaSelecionar)
    val descricao:TextView = itemView.findViewById(R.id.textDescricaoSelecionarMembro)
    val checkBox:CheckBox = itemView.findViewById(R.id.checkboxSelecionarMembro)
}

}

合作者：

    @IgnoreExtraProperties
data class Collaborators(
    var nomeExibicao: String = "",
    var nomePesquisa: String = "",
    var caminhoFoto: String = "",
    var descricaoPerfil: String = "",
    var id: String = "",
    var isSelected: Boolean = false):Serializable{

}

为什么仅当我重新打开“活动”时才加载数据？ 预先感谢！