如何在ActionbarDrawerToggle中设置退格键来导航到之前的片段？

import android.os.Bundle;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentTransaction;
import android.support.v4.widget.DrawerLayout;
import android.support.v7.app.ActionBarDrawerToggle;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.MenuItem;

public class MainActivity extends AppCompatActivity {

    private DrawerLayout drawerLayout;
    private ActionBarDrawerToggle drawerToggle;
    private FragmentManager fragmentManager;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        Toolbar toolbar = findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

        drawerLayout = findViewById(R.id.drawer_layout);
        drawerToggle = new ActionBarDrawerToggle(this, drawerLayout, toolbar, R.string.abc_action_bar_up_description);
        drawerLayout.addDrawerListener(drawerToggle);

        fragmentManager = getSupportFragmentManager();

        if (savedInstanceState == null) {
            // 初始化显示的Fragment
            FragmentTransaction transaction = fragmentManager.beginTransaction();
            transaction.replace(R.id.content_frame, new HomeFragment());
            transaction.commit();
        }
    }

    @Override
    protected void onPostCreate(Bundle savedInstanceState) {
        super.onPostCreate(savedInstanceState);
        drawerToggle.syncState();
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        if (drawerToggle.onOptionsItemSelected(item)) {
            return true;
        }

        if (item.getItemId() == android.R.id.home) {
            // 退格键被选中
            if (fragmentManager.getBackStackEntryCount() > 0) {
                fragmentManager.popBackStack();
                return true;
            }
        }

        return super.onOptionsItemSelected(item);
    }
}