Boa tarde,

Estou tendo problema ao criar o menu lista alunos, quando tento compilar ele apresenta os erros abaixo:

Error:(158, 41) error: cannot find symbol variable menu_lista_alunos Error:(167, 22) error: cannot find symbol variable menu_enviar_notas

Error:Execution failed for task ':app:compileDebugJavaWithJavac'.

Compilation failed; see the compiler error output for details.

segue o código do Menu:

<menu 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"
    tools:context=".ListaAlunosActivity">

    <item android:id="@+id/menu_enviar_notas"
        android:title="Enviar Notas"
        android:icon="@drawable/ic_enviar"
        app:showAsAction="always" />

</menu>

e o código da classe LIstaAlunoActivity.java

package br.com.espalhaai.agenda;

import android.annotation.TargetApi;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.net.Uri;
import android.os.Build;
import android.support.v4.app.ActivityCompat;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.ContextMenu;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.AdapterView;
import android.widget.Button;
import android.widget.ListView;
import android.widget.Toast;

import java.util.List;

import br.com.espalhaai.agenda.adapter.AlunosAdapter;
import br.com.espalhaai.agenda.dao.AlunoDAO;
import br.com.espalhaai.agenda.modelo.Aluno;

public class ListaAlunoActivity extends AppCompatActivity {

    private static final int CODIGO_SMS = 124;
    private ListView listaAlunos;

    @TargetApi(Build.VERSION_CODES.M)
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_lista_aluno);

        listaAlunos = (ListView) findViewById(R.id.lista_alunos);

        // permissão para sms
        if (checkSelfPermission(android.Manifest.permission.RECEIVE_SMS) != PackageManager.PERMISSION_GRANTED ){
            requestPermissions(new String[] {android.Manifest.permission.RECEIVE_SMS}, CODIGO_SMS);
        }

        listaAlunos.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> lista, View item, int position, long id) {
                Aluno aluno = (Aluno) listaAlunos.getItemAtPosition(position);

                Intent intentVaiParaFormulario = new Intent(ListaAlunoActivity.this, FormularioActivity.class);
                intentVaiParaFormulario.putExtra("aluno",aluno);

                startActivity(intentVaiParaFormulario);
            }
        });

        /*
        listaAlunos.setOnItemLongClickListener(new AdapterView.OnItemLongClickListener() {
            @Override
            public boolean onItemLongClick(AdapterView<?> parent, View view, int position, long id) {
                Toast.makeText(ListaAlunoActivity.this, "CLIQUE LONGO", Toast.LENGTH_SHORT).show();
                return false;
            }
        });
        */
        Button novoAluno = (Button) findViewById(R.id.lista_aluno_novo);
        novoAluno.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intentVaiProFormulario = new Intent(ListaAlunoActivity.this, FormularioActivity.class);
                startActivity(intentVaiProFormulario);
            }
        });

        registerForContextMenu(listaAlunos );
    }

    private void carregaLista() {
        AlunoDAO dao = new AlunoDAO(this);
        List<Aluno> alunos = dao.buscaAlunos();
        dao.close();

        //ArrayAdapter<Aluno> adapter = new ArrayAdapter<Aluno>(this, android.R.layout.simple_list_item_1, alunos);
        //listaAlunos.setAdapter(adapter);
        AlunosAdapter adapter = new AlunosAdapter(this, alunos);
        listaAlunos.setAdapter(adapter);

    }

    @Override
    protected void onResume() {
        super.onResume();
        carregaLista();
    }

    @Override
    public void onCreateContextMenu(ContextMenu menu, View v, final ContextMenu.ContextMenuInfo menuInfo) {
        AdapterView.AdapterContextMenuInfo info = (AdapterView.AdapterContextMenuInfo) menuInfo;
        final Aluno aluno = (Aluno) listaAlunos.getItemAtPosition(info.position);

        MenuItem itemligar = menu.add("Ligar");
        itemligar.setOnMenuItemClickListener(new MenuItem.OnMenuItemClickListener() {
            @Override
            public boolean onMenuItemClick(MenuItem item) {
                if (ActivityCompat.checkSelfPermission(ListaAlunoActivity.this, android.Manifest.permission.CALL_PHONE)
                        != PackageManager.PERMISSION_GRANTED) {
                    ActivityCompat.requestPermissions(ListaAlunoActivity.this, new String[]{android.Manifest.permission.CALL_PHONE}, 123);
                }
                else {
                    Intent intentLigar = new Intent(Intent.ACTION_CALL);
                    intentLigar.setData(Uri.parse("tel:" + aluno.getTelefone()));
                    startActivity(intentLigar);
                }
                return false;
            }
        });


        MenuItem itemSMS =  menu.add("Enviar SMS");
        Intent intentSMS = new Intent(Intent.ACTION_VIEW);
        intentSMS.setData(Uri.parse("sms:" + aluno.getTelefone()));
        itemSMS.setIntent(intentSMS);

        MenuItem itemMapa = menu.add("Visualizar no mapa");
        Intent intentMapa = new Intent(Intent.ACTION_VIEW);
        intentMapa.setData(Uri.parse("geo:0,0?q=" + aluno.getEndereco()));
        itemMapa.setIntent(intentMapa);

        MenuItem itemSite =  menu.add("Visitar site");
        Intent intentSite = new Intent(Intent.ACTION_VIEW);

        String site = aluno.getSite();

        if (!site.startsWith("http://")){
            site = "http://" + site;
        }

        intentSite.setData(Uri.parse(site));
        itemSite.setIntent(intentSite);

        MenuItem deletar = menu.add("Deletar");

        deletar.setOnMenuItemClickListener(new MenuItem.OnMenuItemClickListener() {
            @Override
            public boolean onMenuItemClick(MenuItem item) {
                AlunoDAO dao = new AlunoDAO(ListaAlunoActivity.this);
                dao.deleta(aluno);
                dao.close();

                carregaLista();

                return false;
            }
        });
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.menu_lista_alunos, menu);

        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {

        switch (item.getItemId()){
            case R.id.menu_enviar_notas:
                Toast.makeText(this, "Enviando notas...", Toast.LENGTH_SHORT).show();
                break;
        }

        return super.onOptionsItemSelected(item);
    }

    /*
    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);

        if (requestCode == 123){
            // faz ligação
        }else
        if (requestCode == 124){
            // faz sms
        }
    } */
}

Desde já agradeço a ajuda. Abs