问在android中从碎片管理工具栏的导航和返回按钮

EN

public class MainActivity extends ActionBarActivity {
    private DrawerLayout layoutDrawer;
    private ActionBarDrawerToggle drawerToggler;
    private Stack<Fragment> stack;

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

        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);
        stack = new Stack<Fragment>();
        layoutDrawer = (DrawerLayout) findViewById(R.id.layout_drawer);
        drawerToggler = new ActionBarDrawerToggle(this, layoutDrawer, toolbar,
                R.string.app_name, R.string.app_name);
        layoutDrawer.setDrawerListener(drawerToggler);

        setUpDrawerList();
        pushFragment(new FirstFragment(), true);

        Session.setContext(getApplicationContext());
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        if (drawerToggler.isDrawerIndicatorEnabled()
                && drawerToggler.onOptionsItemSelected(item))
            return true;
        switch (item.getItemId()) {
        case android.R.id.home:
            Toast.makeText(this, "Back from activity", Toast.LENGTH_SHORT)
                    .show();
            return true;
        }
        return super.onOptionsItemSelected(item);
    }

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

    @Override
    public void onBackPressed() {
        popFragment();
    }

    private void setUpDrawerList() {
        ListView listView = (ListView) findViewById(R.id.list_drawer);
        ArrayAdapter<String> adapter = new ArrayAdapter<String>(this,
                android.R.layout.simple_list_item_1,
                Arrays.asList(new String[] { "First Fragment",
                        "Second Fragment" }));
        listView.setAdapter(adapter);
        listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {

            @Override
            public void onItemClick(AdapterView<?> parent, View view,
                    int position, long id) {
                layoutDrawer.closeDrawers();
                drawerToggler.setDrawerIndicatorEnabled(false);
                getSupportActionBar().setDisplayHomeAsUpEnabled(true);
                pushFragment(getFragment(position), true);
            }
        });
    }

    private Fragment getFragment(int pos) {
        switch (pos) {
        case 0:
            return new FirstFragment();
        case 1:
            return new SecondFragment();
        }
        return null;
    }

    public void pushFragment(Fragment fragment, boolean add) {
        FragmentTransaction transation = getSupportFragmentManager()
                .beginTransaction();
        if (add)
            stack.push(fragment);
        transation.replace(R.id.layout_content, fragment);
        transation.commit();
    }

    public void popFragment() {
        if (!stack.isEmpty()) {
            Fragment fragment = stack.elementAt(stack.size() - 2);
            stack.pop();
            pushFragment(fragment, false);
        } else
            super.onBackPressed();
        drawerToggler.setDrawerIndicatorEnabled(stack.size() == 1);
    }

    public void clearBackStack() {
        stack.clear();
    }
}

public class FirstFragment extends Fragment {

    @Override
    public void onActivityCreated(Bundle savedInstanceState) {
        super.onActivityCreated(savedInstanceState);
        setHasOptionsMenu(true);
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {
        return inflater.inflate(R.layout.fragment_first, container, false);
    }

    @Override
    public void onResume() {
        super.onResume();
        ActionBar actionBar = ((ActionBarActivity)getActivity()).getSupportActionBar();
        actionBar.setTitle("First Fragment");
        actionBar.setDisplayHomeAsUpEnabled(true);
        actionBar.setHomeButtonEnabled(true);
    }

    @Override
    public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) {
        super.onCreateOptionsMenu(menu, inflater);
        menu.clear();
        inflater.inflate(R.menu.fragment_menu, menu);
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        switch(item.getItemId()) {
        case android.R.id.home:
            Toast.makeText(getActivity(), "Back from fragment", Toast.LENGTH_SHORT).show();
            getActivity().onBackPressed();
            return true;
        }
        return super.onOptionsItemSelected(item);
    }
}