how fix NullPointerException? [duplicate] - android-recyclerview

Question

This question already has answers here:
What is a NullPointerException, and how do I fix it?
(12 answers)
Closed 3 years ago.
im new in android programing and i want to add JSON to my recyclerview i was getting the adapter not attetched skiping layout but my CustomAdapter is giving me NullPointerException too.
my CustomAdapter
public class CustomAdapter extends RecyclerView.Adapter<CustomAdapter.CustomViewHolder> {
private List<RetroProduct> dataList;
private Context context;
CustomAdapter(Context context, List< RetroProduct > dataList){
this.context = context;
this.dataList = dataList;
}
class CustomViewHolder extends RecyclerView.ViewHolder {
final View mView;
TextView goodsId,categoryTitle,number,title1,title2;
CustomViewHolder(View itemView) {
super(itemView);
mView = itemView;
goodsId = mView.findViewById(R.id.tv_goodsId);
categoryTitle = mView.findViewById(R.id.tv_categoryTitle);
number = mView.findViewById(R.id.tv_number);
title1 = mView.findViewById(R.id.tv_title1);
title2 = mView.findViewById(R.id.tv_title2);
}
}
#NonNull
#Override
public CustomViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
LayoutInflater layoutInflater = LayoutInflater.from(parent.getContext());
View view = layoutInflater.inflate(R.layout.item_row, parent, false);
return new CustomViewHolder(view);
}
#Override
public void onBindViewHolder(CustomViewHolder holder, int position) {
holder.goodsId.setText(dataList.get(position).getGoodsId());
holder.categoryTitle.setText(dataList.get(position).getCategoryTitle());
holder.title1.setText(dataList.get(position).getTitle1());
holder.title2.setText(dataList.get(position).getTitle2());
holder.number.setText(dataList.get(position).getNumber());
}
#Override
public int getItemCount() {
return dataList.size();
}
}
and im getting NullPointerException on
return dataList.size();
what should i do now? give it value or i dont know.
MainActivity
public class MainActivity extends AppCompatActivity {
private CustomAdapter adapter;
private RecyclerView recyclerView;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
GetDataService service =
RetrofitClientInstance.getRetrofitInstance()
.create(GetDataService.class);
Call< List<RetroProduct> > call = service.getAllProducts();
call.enqueue(new Callback<List<RetroProduct>>() {
#Override
public void onResponse(Call<List<RetroProduct>> call,
Response<List<RetroProduct>> response) {
generateDataList(response.body());
LinearLayoutManager manager = new
LinearLayoutManager(MainActivity.this);
recyclerView.setLayoutManager(manager);
recyclerView.setHasFixedSize(true);
recyclerView.setAdapter(adapter);
adapter.notifyDataSetChanged();
}
#Override
public void onFailure(Call<List<RetroProduct>> call, Throwable t)
{
Toast.makeText(MainActivity.this, "null",
Toast.LENGTH_SHORT).show();
}
});
}
private void generateDataList(List<RetroProduct> productList) {
recyclerView = findViewById(R.id.recycler_view);
adapter = new CustomAdapter(this,productList);
}
}

Answer 1

#Override
public int getItemCount() {
if(dataList!=null)
return dataList.size();
else
return 0;
}
Add a null check before calling size() method of a Arraylist as above