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RecyclerView.Adapter supports heterogenous layouts, however, when you have to show multiple arrays of heterogenous object classes, it's difficult to write the code for getItemViewType and onBindViewHolder.

Usually, one has to iterate through each array, doing explicit casts and/or a bunch of ifs, modifying the position value to match the corresponding array.

GroupsRecyclerViewAdapter allows to add groups of items (it could also be a group of a single item, e.g. a header or a footer), easing the development of the use cases mentioned above.

Usage

• Suppose you have the following MyModel class.

public class MyModel {
    private String name;
    private String lastname;

    // getters/setters
}

• Create your view holders.

    private class MyModelViewHolder extends RecyclerView.ViewHolder {

        private final TextView name;
        private final TextView lastname;

        MyModelViewHolder(View itemView) {
            super(itemView);
            name = (TextView) itemView.findViewById(R.id.name);
            lastname = (TextView) itemView.findViewById(R.id.lastname);
        }
    }

• Create your custom Group classes (inheriting from the Group class).

private class MyModelGroup extends Group<MyModel, MyModelViewHolder> {

}

• Inside your group class, specify the view type.

        MyModelGroup(@NonNull List<MyModel> items) {
            super(MODEL_VIEW_TYPE, items);
        }

• Inside your group class, override onBindViewHolder and onCreateViewHolder.

        @Override
        public void onBindViewHolder(MyModelViewHolder holder, int position) {
            MyModel myModel = getItems().get(position);
            holder.name.setText(myModel.getName());
            holder.lastname.setText(myModel.getLastname());
        }

        @Override
        public MyModelViewHolder onCreateViewHolder(@NonNull ViewGroup parent,
                                                    @NonNull LayoutInflater inflater) {
            View v = inflater.inflate(R.layout.my_model_item, parent, false);
            return new MyModelViewHolder(v);
        }

• Finally, instantiate GroupsRecyclerViewAdapter in your Activity/Fragment and add groups.

GroupsRecyclerViewAdapter adapter = new GroupsRecyclerViewAdapter();

Group group = new MyModelGroup(myModelList);
adapter.addGroup(group);

Group group2 = MyModel2Group(myModel2List);
adapter.addGroup(group2);

...