Implementing back navigation with ToolBar and AppCompatActivity

I'm trying to change the Navigation drawer icon back arrow and use it as a back button. But when I getSupportActionBar().setDisplayHomeAsUpEnabled(true); nothing happens.

MainActivity.java

public class MainActivity extends AppCompatActivity
implements NavigationView.OnNavigationItemSelectedListener {
    ActionBarDrawerToggle toggle;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        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);

        toggle = new ActionBarDrawerToggle(
            this, drawer,  R.string.navigation_drawer_open, R.string.navigation_drawer_close);
        drawer.setDrawerListener(toggle);

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

        getSupportActionBar().setDisplayHomeAsUpEnabled(true);
        getSupportActionBar().setHomeButtonEnabled(true);
        getSupportActionBar().setDisplayShowHomeEnabled(true);
    }

    @Override
    public void onPostCreate(Bundle savedInstanceState) {
        super.onPostCreate(savedInstanceState);
        getSupportActionBar().setDisplayHomeAsUpEnabled(true);
//getSupportActionBar().setDisplayShowHomeEnabled(true);
        toggle.syncState();
    }

    @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) {
        if(toggle.onOptionsItemSelected(item)) {
            return true;
        }

// 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.
        int id = item.getItemId();

        if (id == R.id.nav_camera) {
// Handle the camera action
        } else if (id == R.id.nav_gallery) {

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

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

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

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

        }

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

When I change the constructor of the ActionBarDrawerToggle to

toggle = new ActionBarDrawerToggle(this, drawer, **toolbar**, R.string.navigation_drawer_open, R.string.navigation_drawer_close);

the icon does change to back arrow, but it functions like a drawer toggle and not like a back button (because the onOptionsItemSelected is not called).

What is the correct way to make it work?

try this,

toggle.setDrawerIndicatorEnabled(false);

Happy Coding..