How to create base adapter which has type parameter that extends another class and implements an interface?

Question

I have seen the answer to the question,

Java: how to create a generic class that requires a data type which extends a class and implements an interface?

So I attempted to create a base adapter for recyclerview. This is my complete code for the base adapter:

class BaseAdapter<T extends SugarRecord & ModelInterface> extends RecyclerView.Adapter<BaseAdapter.ViewHolder> {

    protected SparseArray<T> modelSparseArray;
    protected Context context;

    private int backgroundResource;



    public BaseAdapter(SparseArray<T> modelSparseArray, Context context) {
        this.modelSparseArray = modelSparseArray;
        this.context = context;
        setupBackgroundResource(context);
    }

    private void setupBackgroundResource(Context context){
        TypedValue typedValue = new TypedValue();
        context.getTheme().resolveAttribute(R.attr.selectableItemBackground, typedValue, true);
        backgroundResource = typedValue.resourceId;
    }

    public class ViewHolder extends RecyclerView.ViewHolder{

        @Bind(R.id.done_indicator)
        CheckBox doneIndicator;

        @Bind(R.id.title)
        TextView title;

        View view;

        public ViewHolder(View itemView) {
            super(itemView);
            ButterKnife.bind(this, itemView);
            view = itemView;
        }
    }

    public void addModel(T model){
        int key = model.getId().intValue();
        int index = modelSparseArray.indexOfKey(key);
        modelSparseArray.append(key, model);
        if(key < 0)
            notifyItemInserted(modelSparseArray.size());
        else
            notifyItemChanged(index);
    }

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

    @Override
    public void onBindViewHolder(ViewHolder holder, final int position) {
        final T model = modelSparseArray.valueAt(position);
        holder.title.setText(model.getTitle());
        holder.doneIndicator.setChecked(model.isDone());
        holder.doneIndicator.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
            @Override
            public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
                model.setDone(isChecked);
                model.save();
            }
        });
    }



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

This question is almost exactly the same as I'm asking, however, the OP of that question gave the answer to the question using a pastebin which, unfortunately, the link is not working anymore.

The error is:

Error:(24, 1) error: BaseAdapter is not abstract and does not override abstract method onBindViewHolder(BaseAdapter.ViewHolder,int) in Adapter
Error:(80, 5) error: method does not override or implement a method from a supertype

The first error is pointing at the start of the class declaration, the second error points at the Override above onBindViewHolder

Answer 1

So I discovered the answer as soon as I posted the question, I'll post this in case anyone need the answer:

Change the RecyclerView.Adapter<BaseAdapter.ViewHolder> to RecyclerView.Adapter<BaseAdapter<T>.ViewHolder>

I originally created the base adapter without the type parameter so it worked with RecyclerView.Adapter<BaseAdapter.ViewHolder> , but after adding the type parameter, I also need to add <T> .

Another solution is making the internal ViewHolder static as @chRyNaN suggested.

Answer 2

Have you tried to change the method signature from

public void onBindViewHolder(ViewHolder holder, final int position)

to

public void onBindViewHolder(ViewHolder holder, int position)

Just make the second parameter NOT final .