RecyclerView com erro - android

Gostaria de saber porque a lista não está aparecendo aqui no meu recyclerview.

Adapter

public class GradeAdapter extends RecyclerView.Adapter<GradeAdapter.RecyclerViewHolder> {

    private BigDecimal[] grades;
    private Integer[] faults;
    private String[] classes;


    public GradeAdapter(BigDecimal[] grades, Integer[] faults, String[] classes) {
        this.grades = grades;
        this.faults = faults;
        this.classes = classes;
    }

    @Override
    public RecyclerViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.recycler_grades, parent, false);
        RecyclerViewHolder recyclerViewHolder = new RecyclerViewHolder(view);

        return recyclerViewHolder;
    }

    @Override
    public void onBindViewHolder(RecyclerViewHolder holder, int position) {
        holder.matter.setText(classes[position]);
        holder.grade.setText((CharSequence) grades[position]);
        holder.fault.setText(faults[position]);
    }

    @Override
    public int getItemCount() {
        return classes == null ? 0 : classes.length;
    }

    public static class RecyclerViewHolder extends RecyclerView.ViewHolder {
        @BindView(R.id.grades)
        TextView grade;
        @BindView(R.id.faults)
        TextView fault;
        @BindView(R.id.classes)
        TextView matter;


        public RecyclerViewHolder(View view) {
            super(view);
            ButterKnife.bind(this, view);

        }
    }
}

Main:

`public class MainActivity extends AppCompatActivity {`

    private RecyclerView recyclerViewGrade;
    private RecyclerView.LayoutManager layoutManager;
private RecyclerView.Adapter adapterGrade;

@Inject
GradeResponse gradeResponse;

@Inject
MainPresenter mainPresenter;

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

    MyApplication.getMainComponent().injectIntoMainActivity(this);// informando ao dagger sobre o uso de um component e a necessidade de injetar dependência

    gradeResponse.getGradeRx();

    recyclerViewGrade = (RecyclerView) findViewById(R.id.boletim);
    layoutManager = new LinearLayoutManager(MainActivity.this);
    recyclerViewGrade.setLayoutManager(layoutManager);
    recyclerViewGrade.setHasFixedSize(true);
    adapterGrade = new GradeAdapter(mainPresenter.getListGrades(), mainPresenter.getListFaults(), mainPresenter.getListClasses());
    recyclerViewGrade.setAdapter(adapterGrade);

MainPresenter:

public class MainPresenter {

    private BigDecimal[] listGrades;
    private Integer[] listFaults;
    private String[] listClasses;

    private RecyclerView recyclerViewGrade;
    private GradeAdapter adapterGrade;

    public void setListGrades(BigDecimal[] listGrades, Integer[] listFaults, String[] listClasses){

        this.listClasses = listClasses;
        this.listFaults = listFaults;
        this.listGrades = listGrades;

        //adapterGrade = new GradeAdapter(listGrades, listFaults, listClasses);
        //recyclerViewGrade.setAdapter(adapterGrade);
    }

Resources - mainactivity.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/activity_main"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="gorick.gradesprojectandroid.MVP.View.MainActivity">

<RelativeLayout
    android:id="@+id/relativeLayout"
    android:layout_width="match_parent"
    android:layout_height="wrap_content">

    <TextView
        android:id="@+id/textView2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentTop="true"
        android:layout_centerHorizontal="true"
        android:text="Notas"
        android:textAlignment="center" />

    <TextView
        android:id="@+id/textView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true"
        android:layout_alignParentTop="true"
        android:layout_marginLeft="27dp"
        android:layout_marginStart="27dp"
        android:text="Matérias" />

    <TextView
        android:id="@+id/textView3"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentTop="true"
        android:layout_marginLeft="55dp"
        android:layout_marginStart="55dp"
        android:layout_toEndOf="@+id/textView2"
        android:layout_toRightOf="@+id/textView2"
        android:text="Faltas" />

</RelativeLayout>

<RelativeLayout
    android:id="@+id/relativeLayout2"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_alignParentLeft="true"
    android:layout_alignParentStart="true"
    android:layout_below="@+id/relativeLayout"
    android:layout_marginTop="15dp">

    <android.support.v7.widget.RecyclerView
        android:id="@+id/boletim"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true"
        android:layout_alignParentTop="true"
        android:layout_marginLeft="28dp"
        android:layout_marginStart="28dp"
        android:scrollbars="vertical" />

</RelativeLayout>


<RelativeLayout
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_centerHorizontal="true">


</RelativeLayout>

<TextView
    android:id="@+id/textView5"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_marginTop="20dp"
    android:text="Próximos Exames:"
    android:textAlignment="center"
    android:textAppearance="@style/Base.TextAppearance.AppCompat.Medium" />

<RelativeLayout
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_marginTop="20dp">

    <TextView
        android:id="@+id/textView4"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentTop="true"
        android:layout_centerHorizontal="true"
        android:text="" />

</RelativeLayout>

Gradeslist.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical" android:layout_width="match_parent"
    android:layout_height="match_parent">

<TextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:id="@+id/grades"
    android:layout_alignParentTop="true"
    android:layout_toRightOf="@+id/classes"
    android:layout_toEndOf="@+id/classes"
    android:layout_marginLeft="31dp"
    android:layout_marginStart="31dp" />

<TextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:id="@+id/faults"
    android:layout_alignParentTop="true"
    android:layout_toRightOf="@+id/classes"
    android:layout_toEndOf="@+id/classes"
    android:layout_marginLeft="109dp"
    android:layout_marginStart="109dp" />

<TextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:id="@+id/classes"
    android:layout_alignParentTop="true"
    android:layout_alignParentLeft="true"
    android:layout_alignParentStart="true" />