I'm doing a shopping list app using SQLitedatabase i used 2 dummy data for testing the database and list but it seems like the list is not correctly passed to the recyclerViewAdapter because the list.size() is 0 in adapter when I use System.out.println to check the if the list size is equal to 2. So below are my codes:

FragmentHome.java :

public class FragmentHome extends Fragment {

private static final String ARG_PARAM1 = "param1";
private static final String ARG_PARAM2 = "param2";
private String mParam1;
private String mParam2;

private RecyclerView recyclerView;
private RecyclerViewAdapter recyclerViewAdapter;

public static DatabaseHandler databaseHandler;
public static List<ShoppingItem> shoppingItemList=new ArrayList<ShoppingItem>();

public FragmentHome() {
    // Required empty public constructor
}

public static FragmentHome newInstance(String param1, String param2) {
    FragmentHome fragment = new FragmentHome();
    Bundle args = new Bundle();
    args.putString(ARG_PARAM1, param1);
    args.putString(ARG_PARAM2, param2);
    fragment.setArguments(args);
    return fragment;
}

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    if (getArguments() != null) {
        mParam1 = getArguments().getString(ARG_PARAM1);
        mParam2 = getArguments().getString(ARG_PARAM2);
    }
}

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    // Inflate the layout for this fragment
    View v=inflater.inflate(R.layout.fragment_home, container, false);

    databaseHandler=new DatabaseHandler(getContext(),null,null,1);
    populateDB();
    populateitemList();

    recyclerView=v.findViewById(R.id.recyclerView);
    recyclerViewAdapter=new RecyclerViewAdapter(shoppingItemList,getActivity());
    recyclerView.setLayoutManager(new LinearLayoutManager(getActivity()));
    recyclerView.setAdapter(recyclerViewAdapter);

    DividerItemDecoration divider=new DividerItemDecoration(getActivity(), DividerItemDecoration.VERTICAL);
    recyclerView.addItemDecoration(divider);

    return v;
}

private void populateDB() {
    //testing
    databaseHandler.addItem(new ShoppingItem(1,"bread","testing1","1","Small",1));
    databaseHandler.addItem(new ShoppingItem(2,"rice","testing2","2","Medium",0));
}

private void populateitemList() {
    if (shoppingItemList!=null){
        shoppingItemList.clear();
    }
    shoppingItemList=databaseHandler.getAllItem();
    for(int i=0;i<shoppingItemList.size();i  ){
        System.out.println(shoppingItemList.get(i).getName());
    }
}

RecyclerViewAdapter.java :

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

List<ShoppingItem> shoppingItemList;
private Context context;

public RecyclerViewAdapter(List<ShoppingItem> shoppingItemList, Context context) {
    this.shoppingItemList = shoppingItemList;
    this.context = context;
}

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

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

    ShoppingItem shoppingItem=shoppingItemList.get(position);
    System.out.println("shoppingList in adapter: "   shoppingItemList);

    if(shoppingItem.getUrgent()==1) {
        holder.imageView.setImageResource(R.drawable.urgent);
    }
    if(shoppingItem.getUrgent()==0) {
        holder.imageView.setImageResource(R.drawable.buy);
    }

    holder.textViewItem.setText(shoppingItem.getName());
    holder.textViewItemQty.setText(shoppingItem.getQuantity());
    holder.textViewItemSize.setText(shoppingItem.getSize());
}

@Override
public int getItemCount() {
    System.out.println(shoppingItemList.size());
    return shoppingItemList.size();
}

public class ViewHolder extends RecyclerView.ViewHolder {

    private ImageView imageView;
    private TextView textViewItem,textViewItemQty,textViewItemSize;

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

        imageView=itemView.findViewById(R.id.imageView);
        textViewItem=itemView.findViewById(R.id.textViewItem);
        textViewItemQty=itemView.findViewById(R.id.textViewItemQty);
        textViewItemSize=itemView.findViewById(R.id.textViewItemSize);

        itemView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

            }
        });
    }
}

CodePudding user response：

You are getting 0 because getItemCount() is getting called before populateitemList() It can be called multiple times in future also decided by recycler view automatically

You need to call notifyDatasetChanged() after adding data to tell recycler view to update itself

private void populateitemList() {
    if (shoppingItemList!=null){
        shoppingItemList.clear();
    }
    shoppingItemList=databaseHandler.getAllItem();
    for(int i=0;i<shoppingItemList.size();i  ){
        System.out.println(shoppingItemList.get(i).getName());
    }
    recyclerViewAdapter.notifyDatasetChanged(); //ADD THIS LINE
}

▲ if its helpful :D