How to change the name in the top bar dynamically when a Fragment is selected?

Question

I want the name in the top bar to change according to the Fragment that is selected, for example, I chose the screen to list customers, so in the bar would appear "List Customers", but I’m not getting, only the initial name. Below is the code of my Activity with Navigationdrawer:

public class MainActivity extends AppCompatActivity
    implements NavigationView.OnNavigationItemSelectedListener {

private String barra;
int id;
FragmentTransaction fragmentTransaction;


@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
    toolbar.setTitle(barra);
    setSupportActionBar(toolbar);

    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.setDrawerListener(toggle);
    toggle.syncState();

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

    fragmentTransaction = getSupportFragmentManager().beginTransaction();
    fragmentTransaction.add(R.id.main_container, new TelaCadastrar());
    fragmentTransaction.commit();
}

@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.main, menu);

    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // Handle action bar item clicks here. The action bar will
    // automatically handle clicks on the Home/Up button, so long
    // as you specify a parent activity in AndroidManifest.xml.
    int id = item.getItemId();

    //noinspection SimplifiableIfStatement
    if (id == R.id.action_settings) {
        return true;
    }

    return super.onOptionsItemSelected(item);
}

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

    if (id == R.id.nav_CadastrarCliente) {
        fragmentTransaction = getSupportFragmentManager().beginTransaction();
        fragmentTransaction.replace(R.id.main_container, new TelaCadastrar());
        barra = "Cadastrar Cliente";
        fragmentTransaction.commit();
    } else if (id == R.id.nav_ListarCliente) {
        fragmentTransaction = getSupportFragmentManager().beginTransaction();
        fragmentTransaction.replace(R.id.main_container, new TelaListar());
        barra = "Listar Clientes";
        fragmentTransaction.commit();
    } else if (id == R.id.nav_Configs) {
        fragmentTransaction = getSupportFragmentManager().beginTransaction();
        fragmentTransaction.replace(R.id.main_container, new TelaConfig());
        barra = "Configurações";
        fragmentTransaction.commit();

    }

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

}

Answer 1

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

    if (id == R.id.nav_CadastrarCliente) {
        fragmentTransaction = getSupportFragmentManager().beginTransaction();
        fragmentTransaction.replace(R.id.main_container, new TelaCadastrar());
        barra = "Cadastrar Cliente";
        fragmentTransaction.commit();
    } else if (id == R.id.nav_ListarCliente) {
        fragmentTransaction = getSupportFragmentManager().beginTransaction();
        fragmentTransaction.replace(R.id.main_container, new TelaListar());
        barra = "Listar Clientes";
        fragmentTransaction.commit();
    } else if (id == R.id.nav_Configs) {
        fragmentTransaction = getSupportFragmentManager().beginTransaction();
        fragmentTransaction.replace(R.id.main_container, new TelaConfig());
        barra = "Configurações";
        fragmentTransaction.commit();

    }
    toolbar.setTitle(barra); //adicione essa linha
    DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
    drawer.closeDrawer(GravityCompat.START);
    return true;
}