App crashed when showing fragment thru Bottom Navigation

Question

Hi i'm making a simple app with bottom navigation to show some fragments. It worked well with showing toast but crashed when trying to show the fragment. This is my code.

MainActivity.java

public class MainActivity extends AppCompatActivity
         {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN, WindowManager.LayoutParams.FLAG_FULLSCREEN);
        setContentView(R.layout.content_main);

        BottomNavigationView bottomNavigationView = (BottomNavigationView) findViewById(R.id.bottom_navigation);
        bottomNavigationView.setOnNavigationItemSelectedListener(new BottomNavigationView.OnNavigationItemSelectedListener() {
            @Override
            public boolean onNavigationItemSelected(@NonNull MenuItem item) {

                Fragment fragment;
                switch (item.getItemId()) {
                    case R.id.action_recents:
                        Toast.makeText(MainActivity.this, "Recents", Toast.LENGTH_SHORT).show();
                        break;
                    case R.id.action_favorites:     
                        //Toast.makeText(MainActivity.this, "Favorites", Toast.LENGTH_SHORT).show();
                        fragment = new FavFragment();
                        loadFragment(fragment); // i think there's something wrong with these lines but found no way to resolve it.
                        break;
                }
                return true;
            }
        });

    }

             private void loadFragment(android.support.v4.app.Fragment fragment) {
                 // load fragment
                 FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
                 transaction.replace(R.id.frame_container, fragment);
                 transaction.addToBackStack(null);
                 transaction.commit();
             }

content_main.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout 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:id="@+id/main"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.example.frg.myapp.MainActivity"
    >  

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

    <android.support.design.widget.BottomNavigationView
        android:id="@+id/bottom_navigation"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        app:itemBackground="@color/colorPrimary"
        app:itemIconTint="@android:color/white"
        app:itemTextColor="@android:color/white"        
        app:menu="@menu/bottom_nav_menu" />

</android.support.constraint.ConstraintLayout>

FavFragment.java. These are created default by android studio so i think there's nothing wrong with these.

public class FavFragment extends Fragment {
    
    private String mParam1;
    private String mParam2;

    private OnFragmentInteractionListener mListener;

    public FavFragment() {
        // Required empty public constructor
    }

    
    public static FavFragment newInstance(String param1, String param2) {
        FavFragment fragment = new FavFragment();
        Bundle args = new Bundle();
        args.putString(ARG_PARAM1, param1);
        args.putString(ARG_PARAM2, param2);
        fragment.setArguments(args);
        return fragment;
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        if (getArguments() != null) {
            mParam1 = getArguments().getString(ARG_PARAM1);
            mParam2 = getArguments().getString(ARG_PARAM2);
        }
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        return inflater.inflate(R.layout.fragment_fav, container, false);
    }

    // TODO: Rename method, update argument and hook method into UI event
    public void onButtonPressed(Uri uri) {
        if (mListener != null) {
            mListener.onFragmentInteraction(uri);
        }
    }

    @Override
    public void onAttach(Context context) {
        super.onAttach(context);
        if (context instanceof OnFragmentInteractionListener) {
            mListener = (OnFragmentInteractionListener) context;
        } else {
            throw new RuntimeException(context.toString()
                    + " must implement OnFragmentInteractionListener");
        }
    }

    @Override
    public void onDetach() {
        super.onDetach();
        mListener = null;
    }

   
    public interface OnFragmentInteractionListener {
        // TODO: Update argument type and name
        void onFragmentInteraction(Uri uri);
    }
}

fragment_fav.xml

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.example.frg.myapp.FavFragment">

    <!-- TODO: Update blank fragment layout -->
    <TextView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:text="@string/hello_blank_fragment" />

</FrameLayout>

bottom_nav_menu.xml

<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto">

    <item
        android:id="@+id/action_recents"
        android:enabled="true"
        android:icon="@drawable/ic_recent"
        android:title="Recent"
        app:showAsAction="ifRoom" />

    <item
        android:id="@+id/action_favorites"
        android:enabled="true"
        android:icon="@drawable/ic_fav"
        android:title="favorite"
        app:showAsAction="ifRoom" />

</menu>

Answer 1

I solved this issue myself. Anyone interested?