private FirebaseAuth autenticacao;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_principal);
    Toolbar toolbar = findViewById(R.id.toolbar);
    toolbar.setTitle("aplicativo teste");
    setSupportActionBar(toolbar);
            FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
    fab.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
                    .setAction("Action", null).show();
        }
    });

    DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
    ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
            this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
    drawer.addDrawerListener(toggle);
    toggle.syncState();

    NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
    navigationView.setItemIconTintList(null);
    navigationView.setNavigationItemSelectedListener(this);

}

@Override
public void onBackPressed() {
    DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
    if (drawer.isDrawerOpen(GravityCompat.START)) {
        drawer.closeDrawer(GravityCompat.START);
    } else {
        super.onBackPressed();
    }
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.principal, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    switch (item.getItemId()){
        case R.id.action_Pagamentos :
            startActivity(new Intent(this, PagamentosActivity.class));
            break;
        case R.id.action_Sair :
            autenticacao = ConfiguracaoFirebase.getFirebaseAutenticacao();
            autenticacao.signOut();
            startActivity(new Intent(this, LoginActivity.class));
            finish();
            break;
    }
    return super.onOptionsItemSelected(item);
}

@SuppressWarnings("StatementWithEmptyBody")
@Override
public boolean onNavigationItemSelected(MenuItem item) {
    // Handle navigation view item clicks here.
    int id = item.getItemId();

    if (id == R.id.nav_destaque) {

    } else if (id == R.id.nav_produtos) {

    } else if (id == R.id.nav_compras) {

    } else if (id == R.id.nav_horario) {
        exibirHorario();
    } else if (id == R.id.nav_avaliar) {
        avaliarApp();
    } else if (id == R.id.nav_compartilhar) {
        compartilharApp();
    } else if (id == R.id.nav_contato) {
        enviarEmail();
    }

    DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
    drawer.closeDrawer(GravityCompat.START);
    return true;
}

//Enviar email
public void enviarEmail(){

    Intent email = new Intent(Intent.ACTION_SEND);
    email.putExtra(Intent.EXTRA_EMAIL, new String[]{"aplicativoteste@gmail.com"});
    email.putExtra(Intent.EXTRA_SUBJECT, "Contato");
    email.putExtra(Intent.EXTRA_TEXT, "Digite sua mensagem aqui");

    email.setType("message/rfc822");

    startActivity(Intent.createChooser(email, "Enviar e-mail com:"));
}

//Compartilhar aplicativo
public void compartilharApp(){

    Intent compartilhar = new Intent(Intent.ACTION_SEND);
    compartilhar.putExtra(Intent.EXTRA_TEXT, "Usei este APP e lembrei de você.");

    compartilhar.setType("text/plain");

    startActivity(Intent.createChooser(compartilhar, "Compartilhar com:"));
}

//Avaliar aplicativo
public void avaliarApp(){
    try {
        startActivity(new Intent(Intent.ACTION_VIEW,
                Uri.parse("market://details?id=" + getPackageName())));
    }catch (ActivityNotFoundException e) {
        startActivity(new Intent(Intent.ACTION_VIEW,
                Uri.parse("http://play.google.com/store/apps/details?id=" + getPackageName())));
    }
}

//Horario de funcionamento
public void exibirHorario(){
    AlertDialog.Builder dialog = new AlertDialog.Builder(this);
    dialog.setTitle("Horário de funcionamento");
    dialog.setMessage("Seg. a Qui. -> 17h - 22hnSex. e Sáb. -> 17h - 00h");
    dialog.setCancelable(false);
    dialog.setNeutralButton("Fechar", new DialogInterface.OnClickListener() {
        @Override
        public void onClick(DialogInterface dialog, int i) {
            dialog.dismiss();
        }
    });

    dialog.create();
    dialog.show();

}