How to save fragment state : Bottom Navigation View with fragments android

Question

Im creating a app with three sections home,color,profile I'm using bottom navigation view with fragments to achieve this.

App UI Here is my code: Main Activity on create method:


final HomeFragment homeFragment = new HomeFragment();
final ColorFragment colorFragment = new ColorFragment();
final ProfileFragment profileFragment = new ProfileFragment();
        
bottomNavigationView.setOnNavigationItemSelectedListener(new BottomNavigationView.OnNavigationItemSelectedListener() {
            @Override
            public boolean onNavigationItemSelected(@NonNull MenuItem item) {
                Fragment active = homeFragment;
                switch (item.getItemId()){
                    case R.id.action_home:
                        active = homeFragment;
                        break;
                        //return true;
                    case R.id.action_color:
                        active = colorFragment;
                        break;
                    case R.id.action_profile:
                        active = profileFragment;
                        break;
                    default:
                        active = homeFragment;
                        break;
                }
                //Loading the fragment on click
                fragmentManager.beginTransaction().replace(R.id.fragment_container,active).commit();
                return true;
            }
        });

Im using fragment manager to load the fragment in my Main Activity which comes with below problem.

1.It reloads the fragment each time I click on the bottom navigation icon.(Im getting data from firebase this will be costly )

I have read many articles regarding this,i found solutions like below:

Using hiding the fragments on creation of activity

fragmentManager.beginTransaction().add(R.id.fragment_container, profileFragment, "3").hide(profileFragment).commit();
        fragmentManager.beginTransaction().add(R.id.fragment_container, colorFragment, "2").hide(colorFragment).commit();
        fragmentManager.beginTransaction().add(R.id.fragment_container,homeFragment, "1").commit();

Above solution loads all the fragments on the creation of activity which isn't a efficient scnario

Using NavHost : It refresh the fragment every time.

This also not working for me.

Please Help:

What I want to acheive: 1.The fragment should only load when I click on the icon for the first time. 2.All the fragments should not load at the time of activity creation. 3.When I revist the fragment It should not load again, I should stay at previous state ex. scrolled till 25th card

//Its should be like playstore,youtube where when we click on icon it loads the data, when we revisit the state will be there.

score 1 · Answer 1 · answered Aug 19 '20 at 19:03

You either need to use extension function provided by Google for BottomNavigationView or use a ViewPager/ViewPager2 to have each fragment have it's own back stack and going back to exact same fragment instead of creating root fragment over and over again. Both solutions require you to have NavHostFragment as root of each tab. You can check out the samples in this repo.

score 0 · Answer 2 · answered Aug 19 '20 at 19:14

0

You can either use a FragmentPagerAdapter or ViewPager2. I refer you to two answers for a similar question:

1- FragmentPagerAdapter

2- ViewPager2

answered Aug 19 '20 at 19:14

Armin

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How to save fragment state : Bottom Navigation View with fragments android

2 Answers2