НПЭ в надувном

У меня проблема с неожиданным исключением NullPointerExpception в

View view = inflater.inflate(R.layout.fragment_weight, container, false);

Интересно, почему это не работает? Я посмотрел учебник, и все было как в моем коде, и работало хорошо. Вот весь мой код:

public class AddWeightFragment extends Fragment {
Button button2;
TextView textView6;
MaterialCalendarView calendarView;

@Nullable
@Override
public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
    View view = inflater.inflate(R.layout.fragment_weight, container, false);
    button2 = view.findViewById(R.id.button2);
    textView6 = view.findViewById(R.id.textView6);
    calendarView = view.findViewById(R.id.calendarView);
    calendarView.setDateSelected(CalendarDay.today(), true);
    button2.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            textView6.setText(calendarView.getSelectedDate().toString());
            Toast.makeText(getContext(), calendarView.getSelectedDate().toString(), Toast.LENGTH_SHORT).show();
        }
    });

    return view;
}
}

Logcat:

 android.view.InflateException: Binary XML file line #9: Attempt to invoke virtual method 'boolean java.lang.String.equals(java.lang.Object)' on a null object reference
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'boolean java.lang.String.equals(java.lang.Object)' on a null object reference

fragment_weight.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:id = "@+id/relativeLayout"
    android:layout_width = "match_parent"
    android:layout_height = "match_parent">

    <view
        android:id = "@+id/calendarView"
        android:layout_width = "wrap_content"
        android:layout_height = "wrap_content"
        android:layout_alignParentStart = "true"
        android:layout_alignParentLeft = "true"
        android:layout_alignParentTop = "true"
        android:layout_alignParentEnd = "true"
        android:layout_alignParentRight = "true"
        android:layout_marginStart = "147dp"
        android:layout_marginLeft = "147dp"
        android:layout_marginTop = "16dp"
        android:layout_marginEnd = "209dp"
        android:layout_marginRight = "209dp"
        app:layout_constraintEnd_toEndOf = "parent"
        app:layout_constraintStart_toStartOf = "parent"
        app:layout_constraintTop_toTopOf = "parent"
        app:layout_constraintVertical_bias = "0.0"
        app:mcv_tileHeight = "40dp"
        app:mcv_tileWidth = "50dp" />

    <Button
        android:id = "@+id/button2"
        android:layout_width = "wrap_content"
        android:layout_height = "wrap_content"
        android:layout_alignParentBottom = "true"
        android:layout_centerHorizontal = "true"
        android:layout_marginBottom = "209dp"
        android:text = "Button" />

    <TextView
        android:id = "@+id/textView6"
        android:layout_width = "wrap_content"
        android:layout_height = "wrap_content"
        android:layout_centerVertical = "true"
        android:layout_marginStart = "-209dp"
        android:layout_toEndOf = "@+id/calendarView"
        android:text = "TextView" />


</RelativeLayout>