Is there an addHeaderView equivalent for RecyclerView?

Question

I\'m looking for an equivalent to addHeaderView for a recycler view. Basically I want to have an image with 2 buttons be added as a header to the listview. Is there a differ

Answer 1

I have implemented the same approach proposed by EC84B4 answer, but I abstracted RecycleViewAdapter and make it easily resuable by means of interfaces.

So in order to use my approach you should add following base classes and interfaces to your project:

1) Interface that provides data for Adapter (collection of generic type T, and additional parameters (if needed) of generic type P)

public interface IRecycleViewListHolder{
            P getAdapterParameters();
            T getItem(int position);
            int getSize();
    }

2) Factory for binding your items (header/item):

public interface IViewHolderBinderFactory {
        void bindView(RecyclerView.ViewHolder holder, int position,IRecycleViewListHolder dataHolder);
}

3) Factory for viewHolders (header/items):

public interface IViewHolderFactory {
    RecyclerView.ViewHolder provideInflatedViewHolder(int viewType, LayoutInflater layoutInflater,@NonNull ViewGroup parent);
}

4) Base class for Adapter with Header:

public class RecycleViewHeaderBased extends RecyclerView.Adapter{

    public final static int HEADER_TYPE = 1;
    public final static int ITEM_TYPE = 0;
    private final IRecycleViewListHolder dataHolder;
    private final IViewHolderBinderFactory binderFactory;
    private final IViewHolderFactory viewHolderFactory;

    public RecycleViewHeaderBased(IRecycleViewListHolder dataHolder, IViewHolderBinderFactory binderFactory, IViewHolderFactory viewHolderFactory) {
        this.dataHolder = dataHolder;
        this.binderFactory = binderFactory;
        this.viewHolderFactory = viewHolderFactory;
    }

    @NonNull
    @Override
    public RecyclerView.ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        LayoutInflater layoutInflater = LayoutInflater.from(parent.getContext());
        return viewHolderFactory.provideInflatedViewHolder(viewType,layoutInflater,parent);
    }

    @Override
    public void onBindViewHolder(@NonNull RecyclerView.ViewHolder holder, int position) {
            binderFactory.bindView(holder, position,dataHolder);
    }

    @Override
    public int getItemViewType(int position) {
        if(position == 0)
            return HEADER_TYPE;
        return ITEM_TYPE;
    }

    @Override
    public int getItemCount() {
        return dataHolder.getSize()+1;
    }
}

---

Usage example:

1) IRecycleViewListHolder implementation:

public class AssetTaskListData implements IRecycleViewListHolder, GroupedRecord> {
    private List> assetCountList;
    private GroupedRecord record;

    public AssetTaskListData(Map assetCountListSrc, GroupedRecord record) {
        this.assetCountList =  new ArrayList<>();
        for(Object  entry: assetCountListSrc.entrySet().toArray()){
            Map.Entry entryTyped = (Map.Entry)entry;
            assetCountList.add(entryTyped);
        }
        this.record = record;
    }

    @Override
    public GroupedRecord getAdapterParameters() {
        return record;
    }

    @Override
    public Map.Entry getItem(int position) {
        return assetCountList.get(position-1);
    }

    @Override
    public int getSize() {
        return assetCountList.size();
    }
}

2) IViewHolderBinderFactory implementation:

public class AssetTaskListBinderFactory implements IViewHolderBinderFactory, GroupedRecord> {
    @Override
    public void bindView(RecyclerView.ViewHolder holder, int position, IRecycleViewListHolder, GroupedRecord> dataHolder) {
        if (holder instanceof AssetItemViewHolder) {
            Integer assetId = dataHolder.getItem(position).getKey();
            Integer assetCount = dataHolder.getItem(position).getValue();
            ((AssetItemViewHolder) holder).bindItem(dataHolder.getAdapterParameters().getRecordId(), assetId, assetCount);
        } else {
            ((AssetHeaderViewHolder) holder).bindItem(dataHolder.getAdapterParameters());
        }
    }
}

3) IViewHolderFactory implementation:

public class AssetTaskListViewHolderFactory implements IViewHolderFactory {
    private IPropertyTypeIconMapper iconMapper;
    private ITypeCaster caster;

    public AssetTaskListViewHolderFactory(IPropertyTypeIconMapper iconMapper, ITypeCaster caster) {
        this.iconMapper = iconMapper;
        this.caster = caster;
    }

    @Override
    public RecyclerView.ViewHolder provideInflatedViewHolder(int viewType, LayoutInflater layoutInflater, @NonNull ViewGroup parent) {
        if (viewType == RecycleViewHeaderBased.HEADER_TYPE) {
            AssetBasedHeaderItemBinding item = DataBindingUtil.inflate(layoutInflater, R.layout.asset_based_header_item, parent, false);
            return new AssetHeaderViewHolder(item.getRoot(), item, caster);
        }
        AssetBasedListItemBinding item = DataBindingUtil.inflate(layoutInflater, R.layout.asset_based_list_item, parent, false);
        return new AssetItemViewHolder(item.getRoot(), item, iconMapper, parent.getContext());
    }
}

4) Deriving adapter

public class AssetHeaderTaskListAdapter extends RecycleViewHeaderBased, GroupedRecord> {
   public AssetHeaderTaskListAdapter(IRecycleViewListHolder, GroupedRecord> dataHolder,
                                      IViewHolderBinderFactory binderFactory,
                                      IViewHolderFactory viewHolderFactory) {
        super(dataHolder, binderFactory, viewHolderFactory);
    }
}

5) Instantiate adapter class:

private void setUpAdapter() {
        Map objectTypesCountForGroupedTask = groupedTaskRepository.getObjectTypesCountForGroupedTask(this.groupedRecordId);
        AssetTaskListData assetTaskListData = new AssetTaskListData(objectTypesCountForGroupedTask, getGroupedRecord());
        adapter = new AssetHeaderTaskListAdapter(assetTaskListData,new AssetTaskListBinderFactory(),new AssetTaskListViewHolderFactory(iconMapper,caster));
        assetTaskListRecycler.setAdapter(adapter);
    }

P.S.: AssetItemViewHolder, AssetBasedListItemBinding, etc. my application own structures that should be swapped by your own, for your own purposes.