MainActivity.java

public class MainActivity extends AppCompatActivity {

    public static final String CONST_CHAVE_ALUNO = "Aluno";
    private AlunoDAO dao;
    private ListaAlunosAdapter adapter;

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        setTitle("Lista de alunos");
        dao = new AlunoDAO();

        attachListeners();
        popularLista();
        configuraLista();
    }

    @Override
    protected void onResume() {
        super.onResume();
        adapter.clear();
        adapter.addAll(dao.getAlunos());
    }

    @Override
    public void onCreateContextMenu(ContextMenu menu, View v, ContextMenu.ContextMenuInfo menuInfo) {
        super.onCreateContextMenu(menu, v, menuInfo);
        getMenuInflater().inflate(R.menu.activity_main_menu, menu);
    }

    @Override
    public boolean onContextItemSelected(@NonNull MenuItem item) {
        AdapterView.AdapterContextMenuInfo info = (AdapterView.AdapterContextMenuInfo) item.getMenuInfo();
        Aluno a = (Aluno) adapter.getItem(info.position);
        if(item.getItemId() == R.id.activity_main_menu){
            dao.remove(a);
            adapter.remove(a);
        }
        return super.onContextItemSelected(item);
    }

    private void popularLista() {
        dao.salvar(new Aluno("Pedro", "88888","perocaegra@gmail.com"));
        dao.salvar(new Aluno("Alex", "2011","alex@gmail.com"));
        dao.salvar(new Aluno("Steve", "2009","steve@gmail.com"));
        dao.salvar(new Aluno("Notch", "77777","deus_notch@gmail.com"));
    }

    private void attachListeners() {
        FloatingActionButton bot = findViewById(R.id.floatingActionButton2);
        bot.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                abrirFormulario(null);
            }
        });
        ListView listaAlunos = (ListView) findViewById(R.id.activity_main_listView);
        listaAlunos = findViewById(R.id.activity_main_listView);
        listaAlunos.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                Aluno a = (Aluno) parent.getItemAtPosition(position);
                Log.i("TestesNucleares", "Aluno: " + a.getNome()  + " (" + position + ")");
                abrirFormulario(a);
            }
        });
    }

    private void abrirFormulario(Aluno a) {
        Intent intencao = new Intent(MainActivity.this, FormularioAlunoActivity.class);
        if(a != null){
            intencao.putExtra(CONST_CHAVE_ALUNO,a);
        }
        startActivity(intencao);
    }



    private void configuraLista() {
        List<Aluno> alunos = dao.getAlunos();
        adapter = new ListaAlunosAdapter(this);
        ListView listaAlunos = (ListView) findViewById(R.id.activity_main_listView);
        listaAlunos.setAdapter(adapter);
        registerForContextMenu(listaAlunos);
    }

}