Go back to the previous Fragment by clicking the Back Phone button?

Question

I’m trying to implement the functionality of going back and appearing to me the fragment in which I was previously.

That is: fragment1, Fragment 2, Fragment 3 and Fragment 4.

I can go from Fragment 1 to 2, 3 and 4 and so on, since, I have a bottomNavigation. What happens is that when I click the back button on the phone the app turns off and I can’t get back to the previous Fragment...

I’ve seen countless codes, but none of them could help me.

This is part of my MainActivity of BottomNavigation:

    BottomNavigationView navigation = findViewById(R.id.navigation);
    navigation.setOnNavigationItemSelectedListener(mOnNavigationItemSelectedListener);
    navigation.setSelectedItemId(R.id.navigation_user);
}

private BottomNavigationView.OnNavigationItemSelectedListener mOnNavigationItemSelectedListener
            = new BottomNavigationView.OnNavigationItemSelectedListener() {

        @Override
        public boolean onNavigationItemSelected(@NonNull MenuItem item) {
            switch (item.getItemId()) {
                case R.id.navigation_user:
                    Navigation.findNavController(MainActivity.this, R.id.navHostFragment).navigate(R.id.user_dest);
                    activeFragment = new UserFragment();
                    return true;
                case R.id.navigation_maps:
                    Navigation.findNavController(MainActivity.this, R.id.navHostFragment).navigate(R.id.maps_dest, bundle);
                    activeFragment = new MapsFragment();
                    return true;
                case R.id.navigation_history:
                    Navigation.findNavController(MainActivity.this, R.id.navHostFragment).navigate(R.id.resume_dest);
                    activeFragment = new HistoryFragment();
                    return true;

            }
            return false;
        }
};

A code I saw (most of the codes used the FragmentManager):

FragmentManager fragmentManager = getFragmentManager();
FragmentTransaction fragmentTransaction = 
fragmentManager.beginTransaction();
fragmentTransaction.replace(..............);
fragmentTransaction.addToBackStack(null);
fragmentTransaction.commit(); 

I don’t know where to put these pieces of code or what parameters to put on fragmentTransaction.replace().

Some kind soul to help me?

Answer 1

In fact the user should use the:

getFragmentManager(). popBackStack()

Sort of like this:

@Override
public void onBackPressed(){
    FragmentManager fm = getFragmentManager();
    if (fm.getBackStackEntryCount() > 0) {
        Log.i("MainActivity", "popping backstack");
        fm.popBackStack();
    } else {
        Log.i("MainActivity", "nothing on backstack, calling super");
        super.onBackPressed();  
    }
}

More information are here: https://developer.android.com/reference/android/app/FragmentManager.html#popBackStack()

Answer 2

This method makes have the event button back from mobile:

@Override
    public void onBackPressed() {
        super.onBackPressed();
    }

Use it to call the previous Fragment.