Navigation drawer backstack, how to get the actionbar title to change with fragment on back click - android-fragments

Question

so i managed to get a stock navigation drawer to work and the action bar title to change with the fragments selected. I've also managed to get the backstack working easy peasy.
What i can't figure out how to do is get the action bar title to change back with the back click. google documentations says to add a onBackStackChangedListener:
getSupportFragmentManager().addOnBackStackChangedListener(
new FragmentManager.OnBackStackChangedListener() {
public void onBackStackChanged() {
// Update your UI here.
}
});
but i'm at a lost where to place it? they say when i .commit to changes so i assumed it was placed after
if (id == R.id.nav_spatial_awareness) {
setTitle("Spatial Awareness");
SpatialAwareness spatialAwarenessFragment = new SpatialAwareness();
android.support.v4.app.FragmentManager spatialAwarenessManager = getSupportFragmentManager();
spatialAwarenessManager.beginTransaction()
.addToBackStack(null)
.replace(R.id.main_content_layout, spatialAwarenessFragment, spatialAwarenessFragment.getTag())
.commit();
but that didn't work, this is what i tried and all i get is red squigglies
if (id == R.id.nav_spatial_awareness) {
setTitle("Spatial Awareness");
SpatialAwareness spatialAwarenessFragment = new SpatialAwareness();
android.support.v4.app.FragmentManager spatialAwarenessManager = getSupportFragmentManager();
spatialAwarenessManager.beginTransaction()
.addToBackStack(null)
.replace(R.id.main_content_layout, spatialAwarenessFragment, spatialAwarenessFragment.getTag())
.commit();
getSupportFragmentManager().addOnBackStackChangedListener(
new FragmentManager.OnBackStackChangedListener() {
public void onBackStackChanged() {
setTitle("Spatial Awareness");
}
});
please help me noob
so i tried this
if (id == R.id.nav_spatial_awareness) {
setTitle("Spatial Awareness");
final SpatialAwareness spatialAwarenessFragment = new SpatialAwareness();
android.support.v4.app.FragmentManager spatialAwarenessManager = getSupportFragmentManager();
spatialAwarenessManager.beginTransaction()
.addToBackStack(null)
.replace(R.id.main_content_layout, spatialAwarenessFragment, "spatialAwarenessFragmentTag")
.commit();
getSupportFragmentManager().addOnBackStackChangedListener(
new FragmentManager.OnBackStackChangedListener() {
public void onBackStackChanged() {
android.app.Fragment currentBackStackFragment = getFragmentManager().findFragmentByTag("spatialAwarenessFragmentTag");
if(currentBackStackFragment instanceof SpatialAwareness){
setTitle("Spatial");
}
}
});
i gave my fragment a tag and then tried matching the instance and then changing the title, still no good :(

Answer 1

Yes, the solution as mentioned here is to add a FragmentManager.OnBackStackChangedListener to your activity's FragmentManager.
Here is an example from a project I worked on:
(I have a navigation drawer with 7 Fragments and the OverviewFragment is the initial one that opens when the MainActivity opens)
My MainActivity:
public class MainActivity extends AppCompatActivity
implements NavigationView.OnNavigationItemSelectedListener, FragmentManager.OnBackStackChangedListener {
...
#Override
protected void onCreate(Bundle savedInstanceState) {
...
NavigationView navigationView = findViewById(R.id.nav_view);
navigationView.setNavigationItemSelectedListener(this);
if (savedInstanceState == null) {
// open the default fragment
OverviewFragment fragment = new OverviewFragment();
getSupportFragmentManager().beginTransaction()
.add(R.id.fragment_container, fragment).commit();
setTitle(R.string.title_fragment_overview);
}
getSupportFragmentManager().addOnBackStackChangedListener(this);
}
#Override
public boolean onNavigationItemSelected(MenuItem item) {
// Handle navigation view item clicks here.
Fragment fragment = null;
switch (item.getItemId()) {
case R.id.nav_overview:
fragment = new OverviewFragment();
break;
case R.id.nav_schedule:
fragment = new ScheduleFragment();
break;
case R.id.nav_all_tasks:
fragment = new AllTasksFragment();
break;
case R.id.nav_announcements:
fragment = new AnnouncementFragment();
break;
case R.id.nav_my_courses:
fragment = new MyCoursesFragment();
break;
case R.id.nav_map:
fragment = new MapFragment();
break;
case R.id.nav_settings:
fragment = new SettingsFragment();
break;
default:
fragment = new OverviewFragment();
}
getSupportFragmentManager().beginTransaction()
.replace(R.id.fragment_container, fragment)
.addToBackStack(null)
.commit();
drawer.closeDrawer(GravityCompat.START);
return true;
}
#Override
public void onBackStackChanged() {
FragmentManager fragmentManager = getSupportFragmentManager();
Fragment currentFragment =
fragmentManager.findFragmentById(R.id.fragment_container);
if (currentFragment instanceof OverviewFragment) {
setTitle(R.string.title_fragment_overview);
navigationView.getMenu().findItem(R.id.nav_overview).setChecked(true);
}
else if (currentFragment instanceof ScheduleFragment) {
setTitle(R.string.title_fragment_schedule);
navigationView.getMenu().findItem(R.id.nav_schedule).setChecked(true);
}
else if (currentFragment instanceof AllTasksFragment) {
setTitle(R.string.title_fragment_all_tasks);
navigationView.getMenu().findItem(R.id.nav_all_tasks).setChecked(true);
}
else if (currentFragment instanceof MyCoursesFragment) {
setTitle(R.string.title_fragment_my_courses);
navigationView.getMenu().findItem(R.id.nav_my_courses).setChecked(true);
}
else if (currentFragment instanceof AnnouncementFragment) {
setTitle(R.string.title_fragment_announcements);
navigationView.getMenu().findItem(R.id.nav_announcements).setChecked(true);
}
else if (currentFragment instanceof MapFragment) {
setTitle(R.string.title_fragment_map);
navigationView.getMenu().findItem(R.id.nav_map).setChecked(true);
}
else if (currentFragment instanceof SettingsFragment) {
setTitle(R.string.title_fragment_settings);
navigationView.getMenu().findItem(R.id.nav_settings).setChecked(true);
}
}
}
Here's the entire project: https://github.com/FCI-E-campus/fci-e-campus-android