Como manter o shape Oval no RecyclerView?

[Viktor_Souza]

Estou fazendo uns testes de uma implementação que vou usar em um aplicativo usando o RecyclerView, neste app vou ter umas paletas de cores no formato redondo, no XML o preview mostra redondo mas quando rodo o app fica tudo quadrado, como faço para deixar redondo?

Segue os códigos:

Drawable do Icone

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android" android:shape="oval">
<solid android:color=" #408EC9"></solid>
</shape>

XML da Main Activity

    <?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">
    <android.support.v7.widget.RecyclerView
        android:id="@+id/teste_recycler_view"
        android:background="@color/colorPrimaryDark"
        android:layout_width="0dp"
        android:layout_height="50dp"
        android:orientation="horizontal"
        app:layoutManager="android.support.v7.widget.LinearLayoutManager"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="1.0"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        tools:listitem="@layout/item_cor_fundo" />
</android.support.constraint.ConstraintLayout>

XML do Item botão para o Recyclerview

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
    <ImageView
        android:id="@+id/change_background_button"
        android:layout_width="30dp"
        android:layout_height="30dp"
        android:layout_marginStart="10dp"
        android:layout_marginTop="10dp"
        android:width="30dp"
        android:height="30dp"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        tools:background="@drawable/ic_botao_azul"/>
</android.support.constraint.ConstraintLayout>

Classe Main

public class MainActivity extends AppCompatActivity {

        private RecyclerView listaCores;

        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);

            CoresDAO dao = new CoresDAO();

            List<Integer> cores = dao.coresListaDAO;
            listaCores = findViewById(R.id.teste_recycler_view);
            TesteAdapter adapter = new TesteAdapter(cores, this);
            listaCores.setAdapter(adapter);
            LinearLayoutManager linearLayoutManager = new LinearLayoutManager(this,
                    LinearLayoutManager.HORIZONTAL,
                    false);
            listaCores.setLayoutManager(linearLayoutManager);
        }
    }

Adapter

   public class TesteAdapter extends RecyclerView.Adapter<TesteAdapter.TesteViewHolder> {

        private List<Integer> cores;
        private Context context;
        private AdapterView.OnItemClickListener onItemClickListener;

        public TesteAdapter(List<Integer> cores, MainActivity context) {
            this.cores = cores;
            this.context = context;
        }

        public void setOnItemClickListener(AdapterView.OnItemClickListener onItemClickListener) {
            this.onItemClickListener = onItemClickListener;
        }


        public TesteAdapter(List<Integer> cores, Context context) {
            this.cores = cores;
            this.context = context;
        }


        @Override
        public TesteAdapter.TesteViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
            View viewCriada = LayoutInflater.from(context).inflate(R.layout.item_cor_fundo, parent, false);
            return new TesteViewHolder(viewCriada);
        }

        @Override
        public void onBindViewHolder(TesteAdapter.TesteViewHolder holder, int position) {
            Integer cor = cores.get(position);
            ImageView background = holder.itemView.findViewById(R.id.change_background_button);
            background.setBackgroundColor(cor);
        }

        @Override
        public int getItemCount() {
            return cores.size();
        }


        public class TesteViewHolder extends RecyclerView.ViewHolder {
            public TesteViewHolder(@NonNull View itemView) {
                super(itemView);



            }
        }
    }

DAO das Cores

  public class CoresDAO {


        private int azul = Color.parseColor("#408EC9");
        private int branco = Color.parseColor("#FFFFFF");
        private int vermelho = Color.parseColor("#EC2F4B");
        private int verde = Color.parseColor("#9ACD32");
        private int amarelo = Color.parseColor("#f9f256");
        private int lilas = Color.parseColor("#f1cbff");
        private int cinza = Color.parseColor("#d2d4dc");
        private int marrom = Color.parseColor("#a47c48");
        private int roxo = Color.parseColor("#be29ec");



        public List<Integer> coresListaDAO = Arrays.asList(
                azul, branco, vermelho,
                verde, amarelo, lilas,
                cinza, marrom, roxo);


    }

Essas duas fotos mostram o que esta acontecendo, eu gostaria que ficasse tudo redondo e colorido.
a primeira foto é do Preview e a que está com os quadrados coloridos está executando o app