RoomDataBaseSchoolMangement_ThankFullToShaplaApu
## Fragment Use to BackButton.. ##
1. create a custom Toolbar under a layout res.
2. then include to activity main and declare to toolbar_id.
3. Variable declare to toolbar.
4. then toolbar id - findViewById.
5. toolbar set text color.
6. actionbar to set toolbar.
7. back button create a enabled
## getSupportActionBar().setDisplayHomeAsUpEnabled(true);
## getSupportActionBar().setDisplayShowHomeEnabled(true);
8. override to onOptions itemSelected item.
9. check to android.R.id.home - default back button call.
10. Declare to main Fragment type preFragment, currentFragment.
with declare to bollean flag.
11. Create a backPressed method();
want to 2 parameter are Fragment type,
prevFragment, currentFragment.
12. Check to bollean value within fragment transiction.
13. then your logic, preFragment to your Fragment.
and currentFragmet to other Fragment.
14. then Fragment transiction start..
15. Lastly activity to finish.