Android不知道如何解决此索引超出范围FirebaseRecyclerview

Question

I get this error and I dont know how to fix it

java.lang.IndexOutOfBoundsException: Index: 2, Size: 2 at java.util.ArrayList.get(ArrayList.java:411) at com.tijdelijk.firebasetest.Start$1.populateViewHolder(Start.java:69) at com.tijdelijk.firebasetest.Start$1.populateViewHolder(Start.java:64)

I am working with firebase database and based on CategoryId I put the items in a arraylist for the SubCategories my code:

public class CategoryFragment extends Fragment {

View myFragment;

RecyclerView listCategory;
RecyclerView.LayoutManager layoutManager;
FirebaseRecyclerAdapter<Category, CategoryViewHolder> adapter;

FirebaseDatabase database;

DatabaseReference categories;
DatabaseReference subCategory;

public static CategoryFragment newInstance() {
    CategoryFragment fragment = new CategoryFragment();
    return fragment;
}

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

    database = FirebaseDatabase.getInstance();
    categories = database.getReference("Category");
    subCategory = database.getReference("SubCategory");

}

@Nullable
@Override
public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
    myFragment = inflater.inflate(R.layout.fragment_category, container, false);

    listCategory = (RecyclerView) myFragment.findViewById(R.id.listCategory);
    listCategory.setHasFixedSize(true);
    layoutManager = new LinearLayoutManager(container.getContext());
    listCategory.setLayoutManager(layoutManager);

    loadCategories();


    return myFragment;
}

private void loadCategories() {
    adapter = new FirebaseRecyclerAdapter<Category, CategoryViewHolder>(
            Category.class,
            R.layout.category_layout,
            CategoryViewHolder.class,
            categories
    ) {


        @Override
        protected void populateViewHolder(CategoryViewHolder viewHolder, final Category model, int position) {
            viewHolder.category_name.setText(model.getName());
            Picasso.with(getActivity())
                    .load(model.getImage())
                    .into(viewHolder.category_image);

            viewHolder.setItemClickListener(new ItemClickListener() {
                @Override
                public void onClick(View view, int position, boolean isLongClick) {
                    Intent startGame = new Intent(getActivity(), Start.class);
                    Common.categoryId = adapter.getRef(position).getKey();
                    loadSubCategory(Common.categoryId);

                    startActivity(startGame);
                }
            });
        }
    };
    adapter.notifyDataSetChanged();
    listCategory.setAdapter(adapter);
}

private void loadSubCategory(String categoryId) {

    //Clear list if there are old subCategory
    if (Common.subCategoryList.size() > 0) {
        Common.subCategoryList.clear();
    }

    subCategory.orderByChild("CategoryId").equalTo(categoryId)
            .addValueEventListener(new ValueEventListener() {
                @Override
                public void onDataChange(DataSnapshot dataSnapshot) {
                    for (DataSnapshot postSnapshot : dataSnapshot.getChildren()) {
                        SubCategory ques = postSnapshot.getValue(SubCategory.class);
                        Common.subCategoryList.add(ques);
                    }
                }

                @Override
                public void onCancelled(DatabaseError databaseError) {

                    }
                });
    }
}

in this activity I want to display also a recyclerview but this time based on the arraylist I got from the categoryfragment here is my code:

public class Start extends AppCompatActivity {


FirebaseDatabase database;
DatabaseReference subCategory;

FirebaseRecyclerAdapter<SubCategory, SubCategoryViewHolder> adapter;
RecyclerView listSubCategory;
RecyclerView.LayoutManager layoutManager;



@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_start);

    database = FirebaseDatabase.getInstance();
    subCategory = database.getReference("SubCategory");

    listSubCategory = findViewById(R.id.listSubCategory);
    listSubCategory.setHasFixedSize(true);
    layoutManager = new LinearLayoutManager(getBaseContext());
    listSubCategory.setLayoutManager(layoutManager);

    loadSubCategories();
    adapter.notifyDataSetChanged();
    listSubCategory.setAdapter(adapter);
}




private void loadSubCategories() {
    adapter = new FirebaseRecyclerAdapter<SubCategory, SubCategoryViewHolder>(
            SubCategory.class,
            R.layout.subcategory_layout,
            SubCategoryViewHolder.class,
            subCategory
    ) {


        @Override
        protected void populateViewHolder(SubCategoryViewHolder viewHolder, SubCategory model, int position) {
            viewHolder.subcategory_nlname.setText(Common.subCategoryList.get(position).getLatijnseNaam());
            viewHolder.subcategory_ltname.setText(Common.subCategoryList.get(position).getNederlandseNaam());


            viewHolder.setItemClickListener(new ItemClickListener() {
                @Override
                public void onClick(View view, int position, boolean isLongClick) {
                    Intent startGame = new Intent(Start.this, Start.class);
                    Common.categoryId = adapter.getRef(position).getKey();

                    startActivity(startGame);
                }
            });
        }


        };
    }
}

here is my viewholder:

public class SubCategoryViewHolder extends RecyclerView.ViewHolder 
implements View.OnClickListener{

public TextView subcategory_nlname;
public TextView subcategory_ltname;


private ItemClickListener itemClickListener;



 public SubCategoryViewHolder(View itemView) {
        super(itemView);
        subcategory_ltname = itemView.findViewById(R.id.latijnse_naam);
        subcategory_nlname =  itemView.findViewById(R.id.nederlandse_naam);

//        itemView.findViewById(R.id.btnPlay).setOnClickListener(this);
    }

    public void setItemClickListener(ItemClickListener itemClickListener) {
        this.itemClickListener = itemClickListener;
    }

        @Override
        public void onClick(View view) {
            itemClickListener.onClick(view,getAdapterPosition(),false);
        }
    }

Answer 1

IndexOutOfBoundException means that you are trying to access a value that is at an index out of the array.

In your case, you have an array of two values. So you have the keys 0 and 1. As said in the error, your code is trying to access the index 2, which does not exist.

You have to check that you are accessing an index that is in the range of values of the array.

Good day to you.