How do I resolve InflateException: Binary XML file line problem?

Question

I'm going to inflate the recycler view in the home fragment using the Navigation component. There are two problems here.

1. InflateException Issues
2. Only one first index appears in view in ArrayList

here is error message.

Caused by: android.view.InflateException: Binary XML file line #11 in kr.hnu.project:layout/activity_navigation: Binary XML file line #10 in kr.hnu.project:layout/content_navigation: Error inflating class fragment
 Caused by: android.view.InflateException: Binary XML file line #10 in kr.hnu.project:layout/content_navigation: Error inflating class fragment
 Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void kr.hnu.project.MyRecyclerAdapter.notifyDataSetChanged()' on a null object reference
    at kr.hnu.project.ui.home.HomeFragment.init(HomeFragment.java:81)
    at kr.hnu.project.ui.home.HomeFragment.onCreateView(HomeFragment.java:55)

And this is my code.

homefragment.java:

public class HomeFragment extends Fragment {
private final static String setMsg = "SELECT sender, receiver, title, date FROM MessageDB";
DBHelper dbHelper;
SQLiteDatabase readDB;
Cursor cursor;
ArrayList<MyItem> mailItem;
MyRecyclerAdapter myAdapter;
String curUser;

private FragmentHomeBinding binding;

public View onCreateView(@NonNull LayoutInflater inflater,
                         ViewGroup container, Bundle savedInstanceState) {
    HomeViewModel homeViewModel =
            new ViewModelProvider(this).get(HomeViewModel.class);

    binding = FragmentHomeBinding.inflate(inflater, container, false);
    View root = binding.getRoot();
    ViewGroup rootView = (ViewGroup) inflater.inflate(R.layout.fragment_home, container, false);

    NavigationActivity main = (NavigationActivity) getActivity();
    curUser = main.getCurrentUserID();

    dbHelper = new DBHelper(inflater.getContext());
    readDB = dbHelper.getReadableDatabase();
    mailItem = new ArrayList<MyItem>();

    init();

    myAdapter = new MyRecyclerAdapter(mailItem);
    LinearLayoutManager layoutManager = new LinearLayoutManager(getActivity(), LinearLayoutManager.VERTICAL, false);
    binding.recyclerview.setLayoutManager(layoutManager); // 앞에 binding!!!
    binding.recyclerview.setAdapter(myAdapter);

    return root;
}

public void init() {
    cursor = readDB.rawQuery(setMsg, null);
    mailItem.clear();

    while (cursor.moveToNext()) {

        if (curUser.equals(cursor.getString(cursor.getColumnIndexOrThrow("receiver")))) {
            mailItem.add(new MyItem(cursor.getString(cursor.getColumnIndexOrThrow("sender")),
                    cursor.getString(cursor.getColumnIndexOrThrow("title")), cursor.getString(cursor.getColumnIndexOrThrow("date"))
            ));

        }
        cursor.close();
        myAdapter.notifyDataSetChanged();
    }
}

fragment_home.xml:

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/linear"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
tools:context=".ui.home.HomeFragment">

<androidx.recyclerview.widget.RecyclerView
    android:id="@+id/recyclerview"
    android:layout_width="match_parent"
    android:layout_height="match_parent"/>

activity_navigation.xml:

<androidx.drawerlayout.widget.DrawerLayout 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/drawer_layout"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:fitsSystemWindows="true"
tools:openDrawer="start">

<include
    android:id="@+id/app_bar_navigation"
    layout="@layout/app_bar_navigation"
    android:layout_width="match_parent"
    android:layout_height="match_parent" />

<com.google.android.material.navigation.NavigationView
    android:id="@+id/nav_view"
    android:layout_width="wrap_content"
    android:layout_height="match_parent"
    android:layout_gravity="start"
    android:fitsSystemWindows="true"
    app:headerLayout="@layout/nav_header_navigation"
    app:menu="@menu/activity_navigation_drawer" />

</androidx.drawerlayout.widget.DrawerLayout>

content_navigation.xml:

<androidx.constraintlayout.widget.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:layout_width="match_parent"
android:layout_height="match_parent"
app:layout_behavior="@string/appbar_scrolling_view_behavior"
tools:showIn="@layout/app_bar_navigation">

<fragment
    android:id="@+id/nav_host_fragment_content_navigation"
    android:name="androidx.navigation.fragment.NavHostFragment"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    app:defaultNavHost="true"
    app:layout_constraintHorizontal_bias="0.0"
    app:layout_constraintLeft_toLeftOf="parent"
    app:layout_constraintRight_toRightOf="parent"
    app:layout_constraintTop_toTopOf="parent"
    app:navGraph="@navigation/mobile_navigation" />
    </androidx.constraintlayout.widget.ConstraintLayout>

Answer 1

You are calling notifyDataSetChanged() on myAdapter inside init before initializing it. That's why it's throwing NullPointerException.

Move init() call after you've initialized myAdapter

myAdapter = new MyRecyclerAdapter(mailItem);
LinearLayoutManager layoutManager = new LinearLayoutManager(getActivity(), LinearLayoutManager.VERTICAL, false);
binding.recyclerview.setLayoutManager(layoutManager); // 앞에 binding!!!
binding.recyclerview.setAdapter(myAdapter);

init(); //here move it down after initialising myAdapter