How to inflate Hashmap<String,List<Items>> into the Recyclerview

Question

I want that the string of keys must act as header and the list must be inflated under that map key in the RecyclerView.

thanks for any help

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

private WeakHashMap<String, List<VideoItem>> mData = new WeakHashMap<>();
private ArrayList<String> mKeys;
ArrayList<WeakHashMap<String,List<VideoItem>>> hashMapArrayList;

public Adapter(WeakHashMap<String, List<VideoItem>> mData, ArrayList<WeakHashMap<String,List<VideoItem>>> hashMapArrayList) {
    this.mData = mData;
    this.hashMapArrayList=hashMapArrayList;
    mKeys = new ArrayList<String>(mData.keySet());
}

public String getKey(int position)
{
    return (String) mKeys.get(position);
}


@Override
public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
    View v = LayoutInflater.from(parent.getContext()).inflate(R.layout.player_item, parent, false);
    MyViewHolder holder=new MyViewHolder(v);
    return holder;
}

@Override
public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {
    String key = getKey(position);
    WeakHashMap<String, List<VideoItem>> value = hashMapArrayList.get(position);
    MyViewHolder holder1=(MyViewHolder)holder;
    holder1.header.setText(key);
    holder1.value.setText(value.get( key ).get( position ).getDuration());
    Log.v( "KEY",key );
    Log.v( "VALUE", String.valueOf( value ) );
}

@Override
public int getItemCount() {
    return (null != hashMapArrayList ? hashMapArrayList.size() : 0);

}

//    public  ArrayList<WeakHashMap<String,List<VideoItem>>> getItem(int position) {
//        return hashMapArrayList.get(mKeys.get(position));
//    }

@Override
public long getItemId(int position) {
    return position;
}
class MyViewHolder extends RecyclerView.ViewHolder{
    TextView header ;
    TextView value;
    public MyViewHolder(View itemView) {
        super(itemView);
        header= (TextView) itemView.findViewById(R.id.header);
        value= (TextView) itemView.findViewById(R.id.task_name);
    }
}

}

Answer 1

You can achieve it easily with the library SectionedRecyclerViewAdapter. You can group your items into sections and add a header to each section:

class MySection extends StatelessSection {

    String title;
    List<VideoItem> list;

    public MySection(String title, List<VideoItem> list) {
        // call constructor with layout resources for this Section header and items 
        super(R.layout.section_header, R.layout.section_item);

        this.title = title;
        this.list = list;
    }

    @Override
    public int getContentItemsTotal() {
        return list.size(); // number of items of this section
    }

    @Override
    public RecyclerView.ViewHolder getItemViewHolder(View view) {
        // return a custom instance of ViewHolder for the items of this section
        return new MyItemViewHolder(view);
    }

    @Override
    public void onBindItemViewHolder(RecyclerView.ViewHolder holder, int position) {
        MyItemViewHolder itemHolder = (MyItemViewHolder) holder;

        // bind your view here
        itemHolder.tvItem.setText(list.get(position).getName());
    }

    @Override
    public RecyclerView.ViewHolder getHeaderViewHolder(View view) {
        return new SimpleHeaderViewHolder(view);
    }

    @Override
    public void onBindHeaderViewHolder(RecyclerView.ViewHolder holder) {
        MyHeaderViewHolder headerHolder = (MyHeaderViewHolder) holder;

        // bind your header view here
        headerHolder.tvItem.setText(title);
    }
}

Then you set up the RecyclerView with your Sections:

// Create an instance of SectionedRecyclerViewAdapter 
SectionedRecyclerViewAdapter sectionAdapter = new SectionedRecyclerViewAdapter();

// Create your sections with the list of data from your HashMap
for(Map.Entry<String, List<VideoItem>> entry : mData.entrySet()) {
    MySection section = new MySection(entry.getKey(), entry.getValue());
    // add your section to the adapter
    sectionAdapter.addSection(section);

}

// Set up your RecyclerView with the SectionedRecyclerViewAdapter
RecyclerView recyclerView = (RecyclerView) findViewById(R.id.recyclerview);
recyclerView.setLayoutManager(new LinearLayoutManager(getContext()));
recyclerView.setAdapter(sectionAdapter);

If you can't use 3rd party libs you can have a look on how it is implemented here.