Code for fragment:

import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.fragment.app.Fragment;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;

import java.util.ArrayList;
import java.util.List;

public class ListingsActivity extends Fragment {

    RecyclerView recyclerView;
    LinearLayoutManager layoutManager;
    List<ModelClass> itemList = new ArrayList<>();
    Adapter adapter;

    @Nullable
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        // Initialize recycler view
        initData();
        initRecyclerView();
        return inflater.inflate(R.layout.activity_listings, container, false);
    }

    // Add and remove data
    private void initData() {
        itemList.add(new ModelClass(R.drawable.placeholder2, "Bottle","Gently used bottle with replaceable nib", "$10", "Abdallah", "24/05/2002",R.drawable.seperator_line));
        itemList.add(new ModelClass(R.drawable.placeholder2, "Bottle","Gently used bottle with replaceable nib", "$10", "Abdallah", "24/05/2002", R.drawable.seperator_line));
        itemList.add(new ModelClass(R.drawable.placeholder2, "Bottle","Gently used bottle with replaceable nib", "$10", "Abdallah", "24/05/2002", R.drawable.seperator_line));
    }

    // Initialize recyclerView function
    private void initRecyclerView() {
        recyclerView = (RecyclerView) getView().findViewById(R.id.listings_container);
        layoutManager = new LinearLayoutManager(getActivity());
        layoutManager.setOrientation(LinearLayoutManager.VERTICAL);
        recyclerView.setLayoutManager(layoutManager);
        adapter = new Adapter(itemList);
        recyclerView.setAdapter(adapter);
        adapter.notifyDataSetChanged();

    }


}

Code for adapter:

package com.jamdev.handmedown;

import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.TextView;

import androidx.annotation.NonNull;
import androidx.recyclerview.widget.RecyclerView;

import java.util.ArrayList;
import java.util.List;

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

    private List<ModelClass> itemList = new ArrayList<>();

    public Adapter(List<ModelClass> itemList){
        this.itemList = itemList;
    }

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

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

        int resource = itemList.get(position).getListing_pic();
        String title = itemList.get(position).getListing_title();
        String description = itemList.get(position).getListing_description();
        String price = itemList.get(position).getListing_price();
        String owner = itemList.get(position).getListing_owner();
        String date = itemList.get(position).getListing_date();
        int divider = itemList.get(position).getSeperator();

        holder.setData(resource,title,description,price,owner,date,divider);

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

    public class ViewHolder extends RecyclerView.ViewHolder{

        private ImageView listing_pic;
        private TextView listing_title;
        private TextView listing_description;
        private TextView listing_price;
        private TextView listing_owner;
        private TextView listing_date;
        private ImageView seperator;

        public ViewHolder(@NonNull View itemView) {
            super(itemView);

            listing_pic = itemView.findViewById(R.id.listing_pic);
            listing_title = itemView.findViewById(R.id.listing_title);
            listing_description = itemView.findViewById(R.id.listing_description);
            listing_price = itemView.findViewById(R.id.listing_price);
            listing_owner = itemView.findViewById(R.id.listing_owner);
            listing_date = itemView.findViewById(R.id.listing_date);
            seperator = itemView.findViewById(R.id.seperator);

        }

        public void setData(int resource, String title, String description, String price, String owner, String date, int divider) {
            listing_pic.setImageResource(resource);
            listing_title.setText(title);
            listing_description.setText(description);
            listing_price.setText(price);
            listing_owner.setText(owner);
            listing_date.setText(date);
            seperator.setImageResource(divider);
        }
    }
}

Commenting the initRecyclerView() out won't make it crash, and opening the layout alone without commenting out initRecyclerView without the use of a fragment won't make it crash, but no items are displayed. So i have the issue of 1. Crashing when used with fragments 2. Not displaying the items when not used in a fragment

Would greatly appreciate your help

CodePudding user response：

You're calling getView() too early in your initRecyclerView().

getView() returns whatever onCreateView() returned and your onCreateView() has not yet completed. Hence getView() returns null and attempting to call a method on that return value will NPE.

You can move the initRecyclerView() to onViewCreated() to fix that issue.