NavigationDrawer

//////////////////////////////////////////////
// MainActivity (simplified class)
//////////////////////////////////////////////

public class MainActivity extends ActionBarActivity {

    private NavigationDrawerFragment mNavigationDrawerFragment;


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

        mNavigationDrawerFragment = (NavigationDrawerFragment)
                getSupportFragmentManager().findFragmentById(R.id.navigation_drawer);
        mTitle = getTitle();

        // Set up the drawer.
        mNavigationDrawerFragment.setUp(
                R.id.navigation_drawer,
                (DrawerLayout) findViewById(R.id.drawer_layout));

        // Show content for the first menu item
        // when the app launches.
        if (savedInstanceState == null) {
            showContentForNavigationDrawerItem(0);
        }
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        if (mNavigationDrawerFragment.onOptionsItemSelected(item)) {
            return true;
        }
        switch (item.getItemId()) {
            case android.R.id.home:
                FragmentManager fragmentManager = getSupportFragmentManager();
                fragmentManager.popBackStack();
                fragmentManager.executePendingTransactions();
                mNavigationDrawerFragment.toggleDrawerIndicator();
                return true;
            default:
                return super.onOptionsItemSelected(item);
        }
    }

    @Override
    public void onBackPressed() {
        FragmentManager fragmentManager = getSupportFragmentManager();
        fragmentManager.executePendingTransactions();
        if (fragmentManager.getBackStackEntryCount() < 1) {
            super.onBackPressed();
        } else {
            fragmentManager.executePendingTransactions();
            fragmentManager.popBackStack();
            fragmentManager.executePendingTransactions();
            mNavigationDrawerFragment.toggleDrawerIndicator();
        }
    }

}

//////////////////////////////////////////////
// NavigationDrawerFragment (simplified class)
//////////////////////////////////////////////

public class NavigationDrawerFragment extends Fragment {

    private static final String STATE_SELECTED_POSITION = "selected_navigation_drawer_position";

    private ActionBarDrawerToggle mDrawerToggle;

    private DrawerLayout mDrawerLayout;
    private ListView mDrawerListView;
    private View mFragmentContainerView;

    private int mCurrentSelectedPosition = 0;
    private boolean mFromSavedInstanceState;
    private boolean mUserLearnedDrawer;

    public NavigationDrawerFragment() {
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        getFragmentManager().addOnBackStackChangedListener(new FragmentManager.OnBackStackChangedListener() {
            @Override
            public void onBackStackChanged() {
                toggleDrawerIndicator();
            }
        });
        mUserLearnedDrawer = mPreferenceHelper.restoreUserLearnedDrawer();

        if (savedInstanceState != null) {
            mCurrentSelectedPosition = savedInstanceState.getInt(STATE_SELECTED_POSITION);
            mFromSavedInstanceState = true;
        }
    }

    public void toggleDrawerIndicator() {
        int backStackCount = getFragmentManager().getBackStackEntryCount();
        boolean enableIndicator = backStackCount == 0;
        mDrawerToggle.setDrawerIndicatorEnabled(enableIndicator);
    }

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

    public boolean isDrawerOpen() {
        return mDrawerLayout != null && mDrawerLayout.isDrawerOpen(mFragmentContainerView);
    }

    public void setUp(int fragmentId, DrawerLayout drawerLayout) {
        mFragmentContainerView = getActivity().findViewById(fragmentId);
        mDrawerLayout = drawerLayout;
        mDrawerLayout.setDrawerShadow(R.drawable.drawer_shadow, GravityCompat.START);

        ActionBar actionBar = getActionBar();
        actionBar.setDisplayHomeAsUpEnabled(true);
        actionBar.setHomeButtonEnabled(true);

        mDrawerToggle = new ActionBarDrawerToggle(
                getActivity(),                    /* host Activity */
                mDrawerLayout,                    /* DrawerLayout object */
                R.drawable.ic_drawer,             /* nav drawer image to replace 'Up' caret */
                R.string.navigation_drawer_open,  /* "open drawer" description for accessibility */
                R.string.navigation_drawer_close  /* "close drawer" description for accessibility */
        ) {
            @Override
            public void onDrawerClosed(View drawerView) {
                super.onDrawerClosed(drawerView);
                if (!isAdded()) {
                    return;
                }
                toggleDrawerIndicator();
                getActivity().supportInvalidateOptionsMenu(); // calls onPrepareOptionsMenu()
            }

            @Override
            public void onDrawerOpened(View drawerView) {
                super.onDrawerOpened(drawerView);
                if (!isAdded()) {
                    return;
                }
                mDrawerToggle.setDrawerIndicatorEnabled(true);
                if (!mUserLearnedDrawer) {
                    // The user manually opened the drawer;
                    // store this flag to prevent auto-showing
                    // the navigation drawer automatically in the future.
                    mUserLearnedDrawer = true;
                    mPreferenceHelper.storeUserLearnedDrawer(true);
                }
                getActivity().supportInvalidateOptionsMenu(); // calls onPrepareOptionsMenu()
            }
        };

        // If the user hasn't 'learned' about the drawer, open it to introduce them to the drawer,
        // per the navigation drawer design guidelines.
        if (!mUserLearnedDrawer && !mFromSavedInstanceState) {
            mDrawerLayout.openDrawer(mFragmentContainerView);
        }

        // Defer code dependent on restoration of previous instance state.
        mDrawerLayout.post(new Runnable() {
            @Override
            public void run() {
                mDrawerToggle.syncState();
            }
        });

        mDrawerLayout.setDrawerListener(mDrawerToggle);
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        if (mDrawerToggle.isDrawerIndicatorEnabled() &&
                mDrawerToggle.onOptionsItemSelected(item)) {
            return true;
        }
        return super.onOptionsItemSelected(item);
    }

}