(android) How to select singleItem in Recyclerview?

Question

Hello.

I want to implement single item selection function in RecyclerView

RecyclerView's item is made up of TextView only.

When i clicked items, i want to change TextView's background color

I want to click only single item.

But items are clicked only multiple

When I click the first item and then the second item, the background color of the first item should be changed.

This is i wanted.

However i can't change the Text of the previous item in 'Adapter'.

I don't know how to get previous selected View.

How should i do?

Adapter.java

public class RoutineListAdapter extends RecyclerView.Adapter<RoutineListAdapter.ViewHolder> {
//    ArrayList<RoutineListModel> items;
    List<String> items = new ArrayList<>();
    Context context;

    public void addItems(List<String> items) {
        this.items = items;
    }


    @NonNull
    @Override
    public ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        context = parent.getContext();
        LayoutInflater inflater = LayoutInflater.from(context);
        View itemView = inflater.inflate(R.layout.routine_list_item, parent, false);

        return new ViewHolder(itemView);
    }

    @Override
    public void onBindViewHolder(@NonNull ViewHolder holder, int position) {
        holder.setItem(items.get(position));
    }

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

    public class ViewHolder extends RecyclerView.ViewHolder {
        TextView routine;
        boolean isSelected;

        public ViewHolder(@NonNull View itemView) {
            super(itemView);
            routine = itemView.findViewById(R.id.routine_list);
            routine.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    if(isSelected == false) {
                        routine.setBackgroundColor(context.getResources().getColor(R.color.light_green_dark));
                        isSelected = true;
                    }
                    else {
                        routine.setBackgroundColor(context.getResources().getColor(R.color.white));
                        isSelected = false;
                    }
                }
            });
        }

        private void setItem(String item) {
            routine.setText(item);
        }
    }
}

question from:https://stackoverflow.com/questions/65646437/android-how-to-select-singleitem-in-recyclerview

Answer 1

ViewHolder's multiple instances are being created, so each instance has its own isSelected property and its value.

But what you need a singe common variable for all viewholder instance to refere it, hence the selectedPosition in the outer class, so it is only one, and when you click you set the current adapter position value to and with that you must notify the adapter, which will trigger to call the onBindViewHolder for all items and in the setItem() you can put up what you want to set background of views on basis of whatever conditions.

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

//    ArrayList<RoutineListModel> items;
    List<String> items = new ArrayList<>();
    Context context;
    int selectedPosition=-1;
//nothing selected initially

    public void addItems(List<String> items) {
        this.items = items;
    }


    @NonNull
    @Override
    public ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        context = parent.getContext();
        LayoutInflater inflater = LayoutInflater.from(context);
        View itemView = inflater.inflate(R.layout.routine_list_item, parent, false);

        return new ViewHolder(itemView);
    }

    @Override
    public void onBindViewHolder(@NonNull ViewHolder holder, int position) {
        holder.setItem(items.get(position));
    }

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

    public class ViewHolder extends RecyclerView.ViewHolder {
        TextView routine;

        public ViewHolder(@NonNull View itemView) {
            super(itemView);
            routine = itemView.findViewById(R.id.routine_list);
            routine.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    selectedPosition=getAdapterPosition();
                    notifyDataSetChanged();
                }
            });
        }

        private void setItem(String item) {
                    if(selectedPosition== getAdapterPosition()) {
                        routine.setBackgroundColor(context.getResources().getColor(R.color.light_green_dark));
                    }
                    else {
                        routine.setBackgroundColor(context.getResources().getColor(R.color.white));
                    }

            routine.setText(item);
        }
    }