带有 RecyclerView 的片段，没有适配器附加错误

Question

I'm making a tabbed activity with different fragments and one of them contains a recyclerview with just some names at the moment. I have no idea what I've done wrong, I get a warning every time on starting the app that says no adapter attached, skipping layout . I've created and set the adapter to the recyclerview in my fragment, created an adapter with viewholder, and created a class to set the name on the recyclerview.

Here is my fragment class:

public class fragment_main extends Fragment {

    View view;
    private RecyclerView mainrecyclerview;
    private List<MainSchedule> listStr;

    public fragment_main() {}

    @NonNull
    @Override
    public View onCreateView(LayoutInflater inflater, @NonNull ViewGroup container, @NonNull Bundle savedInstanceState) {
        view = inflater.inflate(R.layout.fragment_main, container, false);
        mainrecyclerview = (RecyclerView) view.findViewById(R.id.todayRecyclerView);
        MainRecyclerViewAdapter mainAdapter = new MainRecyclerViewAdapter(getActivity(), listStr);
        mainrecyclerview.setLayoutManager(new LinearLayoutManager(getActivity()));
        mainrecyclerview.setAdapter(mainAdapter);
        return super.onCreateView(inflater, container, savedInstanceState);
    }

    @Override
    public void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        listStr = new ArrayList<>();
        listStr.add(new MainSchedule("one"));
        listStr.add(new MainSchedule("two"));
        listStr.add(new MainSchedule("three"));

    }
}

fragment.xml:

<?xml version="1.0" encoding="utf-8"?>
<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"
    tools:context=".fragment_main">

    <androidx.recyclerview.widget.RecyclerView
        android:id="@+id/todayRecyclerView"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_marginStart="32dp"
        android:layout_marginTop="24dp"
        android:layout_marginEnd="32dp"
        android:layout_marginBottom="250dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

</androidx.constraintlayout.widget.ConstraintLayout>

recyclerviewadapter class:

public class MainRecyclerViewAdapter extends RecyclerView.Adapter<MainRecyclerViewAdapter.ViewHolder> {

    Context mContext;
    List<MainSchedule> mData;

    public MainRecyclerViewAdapter(Context context, List<MainSchedule> data){
        this.mContext = context;
        this.mData = data;
    }

    @NonNull
    @Override
    public ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        View view = LayoutInflater.from(mContext).inflate(R.layout.mainschedule_cards, parent, false);
        return new ViewHolder(view);
    }

    @Override
    public void onBindViewHolder(ViewHolder holder, int position) {

        holder.textView.setText(mData.get(position).getName());

    }

    @Override
    public int getItemCount() {
        return mData.size();
    }

    public static class ViewHolder extends RecyclerView.ViewHolder {

        private TextView textView;

        public ViewHolder(View itemView) {
            super(itemView);
            textView = (TextView) itemView.findViewById(R.id.textViewClass);
        }

    }

}

I've tried many ways of creating the adapter and binding the layout manager to the recyclerview, but nothing seems to work and I get the same error each time.

Answer 1

Problem seems with onCreateView because you're supposed to return view

Replace your fragment_main with code below

public class fragment_main extends Fragment {

    private RecyclerView mainrecyclerview;
    private List<MainSchedule> listStr;

    public fragment_main() {
    }

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

    @Override
    public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);
        listStr = new ArrayList<>();
        listStr.add(new MainSchedule("one"));
        listStr.add(new MainSchedule("two"));
        listStr.add(new MainSchedule("three"));
        mainrecyclerview = (RecyclerView) view.findViewById(R.id.todayRecyclerView);
        MainRecyclerViewAdapter mainAdapter = new MainRecyclerViewAdapter(getActivity(), listStr);
        mainrecyclerview.setLayoutManager(new LinearLayoutManager(getActivity()));
        mainrecyclerview.setAdapter(mainAdapter);
    }
}