Shared Element Transition Not Working Between Parent and Child Fragments (Nested Fragments)

Question

In the Main Activity, I have BottomNavigationView where there are 3 different parent fragments. The parent fragment has recyclerview and on item cl

Answer 1

Shared element transition does not work properly with FragmentTransaction.add method because parent fragment is still alive and resumed. Try

transaction.replace(R.id.child_fragment, newFragment, tag);

Check this discussion thread for more information.

Answer 2

I am trying to implement Shared Element Transition between my two fragments (parent & child) but it's not happening.

Nothing is happening or at least it looks like nothing is happening because you're using only <changeTransform/> and <changeBounds /> in your default_transition.xml. If bounds of both Fragments coincide, there's nothing to "transit".

However, if you add additional animation elements to the file then the transition is actually visible (even if bounds coincide).

Introduction

I have created a sample project similar to yours - BottomNavigationView with a NavHostFragment containing 2 parent Fragments - DashboardFragment and HomeFragment.

Initially, DashboardFragment loads DashboardListFragment that consists of a simple RecyclerView. If any RecyclerView item is clicked then DashboardFragment loads DashboardDetailFragment (bounds in DashboardDetailFragment and DashboardListFragment coincide).

Transition Behaviour

Then, I pretty much reused your showFragmentWithTransition(...) and tried to click each element in the list to check if any transition would be visible - it wasn't.

Hence, I modified the file by adding a simple <slide/> element as below:

<?xml version="1.0" encoding="utf-8"?>
<transitionSet>
    <slide/>
    <changeTransform />
    <changeBounds />
</transitionSet>

And the sliding transition was right there.

I also tried other elements like <fade/> or <explode/> or others - all of them worked just fine too.

Conclusion

Even if a transition is not visible, it doesn't mean it's not happening. You should try other animation elements to see it work.

UPDATE

Since you provided a link to your github code, I peeked into it and brought it to the working condition. I'll leave it up to you to improve it further.

So, basically, your HomeFragment layout file contained both RecyclerView and a placeholder for your child Fragment at the same time. Instead, I split your HomeFragment into 2 entities - one for your parent Fragment HomeFragment containing only the placeholder for any child Fragment and HomeFragmentList containing your previous parent logic.

Then, when a picture is selected, HomeFragment replaces your HomeFragmentList with a ChildFragment. And...it works!

This way, you don't need to use your Activity for creating a child Fragment and it's more independent.

Below, I provide the relevant code that had to be modified.

Code

HomeFragment (new parent)

public class HomeFragment extends Fragment {

    public View onCreateView(@NonNull LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        return inflater.inflate(R.layout.fragment_home, container, false);
    }

    @Override
    public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);

        HomeFragmentList homeFragmentList = new HomeFragmentList();
        FragmentTransaction fragmentTransaction = getChildFragmentManager().beginTransaction();
        fragmentTransaction.replace(R.id.child_fragment, homeFragmentList, homeFragmentList.getClass().getName());
        fragmentTransaction.commit();
    }
}

HomeFragmentList (old parent)

public class HomeFragmentList extends Fragment implements AdapterListener {
    RecyclerView recyclerView;
    private ArrayList<String> images = new ArrayList<>();

    public View onCreateView(@NonNull LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {

        View root = inflater.inflate(R.layout.fragment_home_list, container, false);

        recyclerView = root.findViewById(R.id.recycler_view);
        getImages();
        LinearLayoutManager manager = new LinearLayoutManager(getActivity(), LinearLayoutManager.VERTICAL, false);
        recyclerView = root.findViewById(R.id.recycler_view);
        recyclerView.setLayoutManager(manager);
        AdapterClass adapter = new AdapterClass(this, images);
        recyclerView.setAdapter(adapter);

        return root;
    }

    void getImages() {
        images.add("https://rukminim1.flixcart.com/image/832/832/book/0/1/9/rich-dad-poor-dad-original-imadat2a4f5vwgzn.jpeg?q=70");
        images.add("https://www.seeken.in/wp-content/uploads/2017/06/The-4-Hour-Work-Week.jpeg");
        images.add("https://www.seeken.in/wp-content/uploads/2017/06/Managing-Oneself.jpeg");
        images.add("https://www.seeken.in/wp-content/uploads/2017/07/How-to-Win-Friends-and-Influence-People.jpeg");
        images.add("https://www.seeken.in/wp-content/uploads/2017/07/THINK-LIKE-DA-VINCI-7-Easy-Steps-to-Boosting-your-Everyday-Genius.jpeg");
        images.add("https://www.seeken.in/wp-content/uploads/2017/07/How-To-Stop-Worrying-And-Start-Living.jpg");
        images.add("https://www.seeken.in/wp-content/uploads/2017/08/THE-INTELLIGENT-INVESTOR.jpeg");
        images.add("https://www.seeken.in/wp-content/uploads/2017/08/Awaken-the-Giant-within-How-to-Take-Immediate-Control-of-Your-Mental-Emotional-Physical-and-Financial-Life.jpg");
        images.add("https://www.seeken.in/wp-content/uploads/2017/08/E-MYTH-REVISITED.jpeg");
        images.add("https://images-na.ssl-images-amazon.com/images/I/41axGE4CehL._SX353_BO1,204,203,200_.jpg");
        images.add("https://rukminim1.flixcart.com/image/832/832/book/0/1/9/rich-dad-poor-dad-original-imadat2a4f5vwgzn.jpeg?q=70");

    }

    @Override
    public void itemClicked(int pos, ModelClass object, View view, String transition) {
        MainActivity activity = (MainActivity) getActivity();
        ChildFragment myFragment = new ChildFragment();
        Bundle bundle = new Bundle();
        bundle.putString("IMAGE_URL", object.getItem(pos));
        bundle.putInt("POSITION", pos);
        bundle.putString("TRANSITION_NAME", transition);
        myFragment.setArguments(bundle);
        Log.i("HOME FRAGMENT-DEBUG", transition + "/" + view.getTransitionName());
        showFragmentWithTransition(getParentFragment(), myFragment, ChildFragment.class.getName(), view, transition);
    }

    public void showFragmentWithTransition(Fragment current, Fragment _new, String tag, View sharedView, String sharedElementName) {

        FragmentManager manager = current.getChildFragmentManager();
        FragmentTransaction transaction = manager.beginTransaction();
        if (sharedView != null && sharedElementName != null) {
            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
                current.setSharedElementReturnTransition(TransitionInflater.from(getContext()).inflateTransition(R.transition.default_transition));
                current.setExitTransition(TransitionInflater.from(getContext()).inflateTransition(android.R.transition.no_transition));
                _new.setSharedElementEnterTransition(TransitionInflater.from(getContext()).inflateTransition(R.transition.default_transition));
                _new.setEnterTransition(TransitionInflater.from(getContext()).inflateTransition(android.R.transition.no_transition));
                transaction.addSharedElement(sharedView, sharedElementName);
                Log.i("ACTIVITY-DEBUG", sharedElementName + "/" + sharedView.getTransitionName());
            }
        }
        transaction.replace(R.id.child_fragment, _new, tag);
        transaction.addToBackStack(tag);
        transaction.commit();
    }
}

fragment_home.xml

<?xml version="1.0" encoding="utf-8"?>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <FrameLayout
        android:id="@+id/child_fragment"
        android:layout_width="match_parent"
        android:layout_height="match_parent"/>

</LinearLayout>

fragment_home_list.xml

<?xml version="1.0" encoding="utf-8"?>

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <androidx.coordinatorlayout.widget.CoordinatorLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:background="#FFF">

        <androidx.core.widget.NestedScrollView
            android:id="@+id/home_container"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            app:layout_behavior="@string/appbar_scrolling_view_behavior">

            <RelativeLayout
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:layout_marginTop="15dp"
                android:layout_marginLeft="9dp"
                android:layout_marginRight="9dp">


                <androidx.recyclerview.widget.RecyclerView
                    android:id="@+id/recycler_view"
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:layout_marginTop="5dp"
                    android:orientation="vertical">

                </androidx.recyclerview.widget.RecyclerView>

            </RelativeLayout>

        </androidx.core.widget.NestedScrollView>

        <com.google.android.material.appbar.AppBarLayout
            android:id="@+id/appbar"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:background="#FFF">

            <androidx.appcompat.widget.Toolbar
                android:id="@+id/z_toolbar"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:elevation="4dp">

                <RelativeLayout
                    android:id="@+id/header_container"
                    android:layout_width="match_parent"
                    android:layout_height="56dp">

                    <ImageView
                        android:id="@+id/logo"
                        android:layout_width="30dp"
                        android:layout_height="30dp"
                        android:layout_marginRight="10dp"
                        android:layout_centerVertical="true"
                        android:layout_alignParentLeft="true"
                        android:src="@mipmap/ic_launcher_round"
                        android:contentDescription="@string/app_name" />

                    <TextView
                        android:layout_width="wrap_content"
                        android:layout_height="wrap_content"
                        android:layout_centerVertical="true"
                        android:layout_toRightOf="@+id/logo"
                        android:textColor="#000"
                        android:textSize="16sp"
                        android:text="Home" />

                </RelativeLayout>

            </androidx.appcompat.widget.Toolbar>

        </com.google.android.material.appbar.AppBarLayout>

    </androidx.coordinatorlayout.widget.CoordinatorLayout>
</RelativeLayout>

Remark

Please note that the transition for <changeTransform/> and <changeBounds /> is visible because bounds of a selected View in HomeFragmentList are different from that in the child Fragment.

Answer 3

I'm not sure about the rest of your setup, but for Shared Element Transitions to work correctly, you need to add setReorderingAllowed(true) to your Fragment Transaction like this:

FragmentTransaction transaction = manager.beginTransaction();
transaction.add(R.id.child_fragment, newFragment, tag);
transaction.addToBackStack(tag);
transaction.addSharedElement(sharedView, sharedElementName);
transaction.setReorderingAllowed(true); // Add this
transaction.commit();