Switching between Android Navigation Drawer image and Up caret when using fragments

It's easy as 1-2-3.

If you want to achieve:

1) Drawer Indicator - when no fragments are in the Back Stack or the Drawer is opened

2) Arrow - when some Fragments are in the Back Stack

private FragmentManager.OnBackStackChangedListener        mOnBackStackChangedListener = new FragmentManager.OnBackStackChangedListener() {    @Override    public void onBackStackChanged() {        syncActionBarArrowState();    }};@Overrideprotected void onCreate(Bundle savedInstanceState) {    getSupportActionBar().setDisplayShowHomeEnabled(true);    getSupportActionBar().setDisplayHomeAsUpEnabled(true);    mDrawerToggle = new ActionBarDrawerToggle(            this,                         mDrawerLayout,              R.drawable.ic_navigation_drawer,             0,             0      ) {        public void onDrawerClosed(View view) {            syncActionBarArrowState();        }        public void onDrawerOpened(View drawerView) {            mDrawerToggle.setDrawerIndicatorEnabled(true);        }    };    mDrawerLayout.setDrawerListener(mDrawerToggle);    getSupportFragmentManager().addOnBackStackChangedListener(mOnBackStackChangedListener);}@Overrideprotected void onDestroy() {    getSupportFragmentManager().removeOnBackStackChangedListener(mOnBackStackChangedListener);    super.onDestroy();}private void syncActionBarArrowState() {    int backStackEntryCount =         getSupportFragmentManager().getBackStackEntryCount();    mDrawerToggle.setDrawerIndicatorEnabled(backStackEntryCount == 0);}

3) Both indicators to act according to their shape

@Overridepublic boolean onOptionsItemSelected(MenuItem item) {    if (mDrawerToggle.isDrawerIndicatorEnabled() &&         mDrawerToggle.onOptionsItemSelected(item)) {        return true;    } else if (item.getItemId() == android.R.id.home &&                getSupportFragmentManager().popBackStackImmediate()) {        return true;    } else {        return super.onOptionsItemSelected(item);    }}

P.S. See Creating a Navigation Drawer on Android Developers on other tips about the 3-lines indicator behavior.

You have written that, to implement lower-level fragments, you are replacing the existing fragment, as opposed to implementing the lower-level fragment in a new activity.

I would think that you would then have to implement the back functionality manually: when the user pressed back you have code that pops the stack (e.g. in Activity::onBackPressed override). So, wherever you do that, you can reverse the setDrawerIndicatorEnabled.

I've used next thing:

getSupportFragmentManager().addOnBackStackChangedListener(new FragmentManager.OnBackStackChangedListener() {            @Override            public void onBackStackChanged() {                if(getSupportFragmentManager().getBackStackEntryCount() > 0){                    mDrawerToggle.setDrawerIndicatorEnabled(false);                    getSupportActionBar().setDisplayHomeAsUpEnabled(true);                }                else {                    getSupportActionBar().setDisplayHomeAsUpEnabled(false);                    mDrawerToggle.setDrawerIndicatorEnabled(true);                }            }        });