A SectionedGridRecyclerViewAdapter: use this class to realize a simple sectioned grid `RecyclerView.Adapter`.

README.md

You can use this class to realize a simple sectioned grid RecyclerView.Adapter without changing your code.

The RecyclerView has to use a GridLayoutManager.

This is a porting of the class SimpleSectionedListAdapter provided by Google

If you are looking for a sectioned list RecyclerView.Adapter you can take a look here

Example:

         //Your RecyclerView
        mRecyclerView = (RecyclerView) getActivity().findViewById(R.id.list);
        mRecyclerView.setHasFixedSize(true);
        mRecyclerView.setLayoutManager(new GridLayoutManager(getActivity(),4));

        //Your RecyclerView.Adapter
        mAdapter = new SimpleAdapter(getActivity());

        //This is the code to provide a sectioned grid
        List<SectionedGridRecyclerViewAdapter.Section> sections =
                new ArrayList<SectionedGridRecyclerViewAdapter.Section>();

        //Sections
        sections.add(new SectionedGridRecyclerViewAdapter.Section(0,"Section 1"));
        sections.add(new SectionedGridRecyclerViewAdapter.Section(5,"Section 2"));
        sections.add(new SectionedGridRecyclerViewAdapter.Section(12,"Section 3"));
        sections.add(new SectionedGridRecyclerViewAdapter.Section(14,"Section 4"));
        sections.add(new SectionedGridRecyclerViewAdapter.Section(20,"Section 5"));

        //Add your adapter to the sectionAdapter
        SectionedGridRecyclerViewAdapter.Section[] dummy = new SectionedGridRecyclerViewAdapter.Section[sections.size()];
        SectionedGridRecyclerViewAdapter mSectionedAdapter = new
                SectionedGridRecyclerViewAdapter(getActivity(),R.layout.section,R.id.section_text,mRecyclerView,mAdapter);
        mSectionedAdapter.setSections(sections.toArray(dummy));

        //Apply this adapter to the RecyclerView
        mRecyclerView.setAdapter(mSectionedAdapter);

You can customize the section layout, changing the layout section.xml and changing the code in the SectionedGridRecyclerViewAdapter.SectionViewHolder class and SectionedGridRecyclerViewAdapter#onBindViewHolder method.

item.xml

<?xml version="1.0" encoding="utf-8"?>
<TextView xmlns:android="http://schemas.android.com/apk/res/android"
          android:id="@+id/title"
          android:layout_width="match_parent"
          android:layout_height="130dp"
          android:gravity="center"
          android:layout_margin="4dp"
          android:textColor="#999999"
          android:textStyle="bold"
          android:textSize="22sp"
          android:background="@drawable/item_background"/>

section.xml

<?xml version="1.0" encoding="utf-8"?>

<TextView xmlns:android="http://schemas.android.com/apk/res/android"
          android:layout_width="match_parent"
          android:layout_height="48dp"
          android:gravity="center_vertical"
          android:paddingLeft="16dp"
          android:singleLine="true"
          android:textAllCaps="true"
          android:background="#90CAF9"
          android:textSize="16sp"
          android:id="@+id/section_text"
          android:textStyle="bold" />

SectionedGridRecyclerViewAdapter.java

/**
 * @author Gabriele Mariotti (gabri.mariotti@gmail.com)
 */
public class SectionedGridRecyclerViewAdapter extends RecyclerView.Adapter<RecyclerView.ViewHolder> {

    private final Context mContext;
    private static final int SECTION_TYPE = 0;

    private boolean mValid = true;
    private int mSectionResourceId;
    private int mTextResourceId;
    private LayoutInflater mLayoutInflater;
    private RecyclerView.Adapter mBaseAdapter;
    private SparseArray<Section> mSections = new SparseArray<Section>();
    private RecyclerView mRecyclerView;


    public SectionedGridRecyclerViewAdapter(Context context, int sectionResourceId, int textResourceId,RecyclerView recyclerView,
                                            RecyclerView.Adapter baseAdapter) {

        mLayoutInflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        mSectionResourceId = sectionResourceId;
        mTextResourceId = textResourceId;
        mBaseAdapter = baseAdapter;
        mContext = context;
        mRecyclerView = recyclerView;

        mBaseAdapter.registerAdapterDataObserver(new RecyclerView.AdapterDataObserver() {
            @Override
            public void onChanged() {
                mValid = mBaseAdapter.getItemCount()>0;
                notifyDataSetChanged();
            }

            @Override
            public void onItemRangeChanged(int positionStart, int itemCount) {
                mValid = mBaseAdapter.getItemCount()>0;
                notifyItemRangeChanged(positionStart, itemCount);
            }

            @Override
            public void onItemRangeInserted(int positionStart, int itemCount) {
                mValid = mBaseAdapter.getItemCount()>0;
                notifyItemRangeInserted(positionStart, itemCount);
            }

            @Override
            public void onItemRangeRemoved(int positionStart, int itemCount) {
                mValid = mBaseAdapter.getItemCount()>0;
                notifyItemRangeRemoved(positionStart, itemCount);
            }
        });

        final GridLayoutManager layoutManager = (GridLayoutManager)(mRecyclerView.getLayoutManager());
        layoutManager.setSpanSizeLookup(new GridLayoutManager.SpanSizeLookup() {
            @Override
            public int getSpanSize(int position) {
                return (isSectionHeaderPosition(position))? layoutManager.getSpanCount() : 1 ;
            }
        });
    }


    public static class SectionViewHolder extends RecyclerView.ViewHolder {

        public TextView title;

        public SectionViewHolder(View view,int mTextResourceid) {
            super(view);
            title = (TextView) view.findViewById(mTextResourceid);
        }
    }

    @Override
    public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int typeView) {
        if (typeView == SECTION_TYPE) {
            final View view = LayoutInflater.from(mContext).inflate(mSectionResourceId, parent, false);
            return new SectionViewHolder(view,mTextResourceId);
        }else{
            return mBaseAdapter.onCreateViewHolder(parent, typeView -1);
        }
    }

    @Override
    public void onBindViewHolder(RecyclerView.ViewHolder sectionViewHolder, int position) {
        if (isSectionHeaderPosition(position)) {
            ((SectionViewHolder)sectionViewHolder).title.setText(mSections.get(position).title);
        }else{
            mBaseAdapter.onBindViewHolder(sectionViewHolder,sectionedPositionToPosition(position));
        }

    }

    @Override
    public int getItemViewType(int position) {
        return isSectionHeaderPosition(position)
                ? SECTION_TYPE
                : mBaseAdapter.getItemViewType(sectionedPositionToPosition(position)) +1 ;
    }


    public static class Section {
        int firstPosition;
        int sectionedPosition;
        CharSequence title;

        public Section(int firstPosition, CharSequence title) {
            this.firstPosition = firstPosition;
            this.title = title;
        }

        public CharSequence getTitle() {
            return title;
        }
    }


    public void setSections(Section[] sections) {
        mSections.clear();

        Arrays.sort(sections, new Comparator<Section>() {
            @Override
            public int compare(Section o, Section o1) {
                return (o.firstPosition == o1.firstPosition)
                        ? 0
                        : ((o.firstPosition < o1.firstPosition) ? -1 : 1);
            }
        });

        int offset = 0; // offset positions for the headers we're adding
        for (Section section : sections) {
            section.sectionedPosition = section.firstPosition + offset;
            mSections.append(section.sectionedPosition, section);
            ++offset;
        }

        notifyDataSetChanged();
    }

    public int positionToSectionedPosition(int position) {
        int offset = 0;
        for (int i = 0; i < mSections.size(); i++) {
            if (mSections.valueAt(i).firstPosition > position) {
                break;
            }
            ++offset;
        }
        return position + offset;
    }

    public int sectionedPositionToPosition(int sectionedPosition) {
        if (isSectionHeaderPosition(sectionedPosition)) {
            return RecyclerView.NO_POSITION;
        }

        int offset = 0;
        for (int i = 0; i < mSections.size(); i++) {
            if (mSections.valueAt(i).sectionedPosition > sectionedPosition) {
                break;
            }
            --offset;
        }
        return sectionedPosition + offset;
    }

    public boolean isSectionHeaderPosition(int position) {
        return mSections.get(position) != null;
    }


    @Override
    public long getItemId(int position) {
        return isSectionHeaderPosition(position)
                ? Integer.MAX_VALUE - mSections.indexOfKey(position)
                : mBaseAdapter.getItemId(sectionedPositionToPosition(position));
    }

    @Override
    public int getItemCount() {
        return (mValid ? mBaseAdapter.getItemCount() + mSections.size() : 0);
    }

}

SimpleAdapter.java

/**
 * @author Gabriele Mariotti (gabri.mariotti@gmail.com)
 */
public class SimpleAdapter extends RecyclerView.Adapter<SimpleAdapter.SimpleViewHolder> {
    private static final int COUNT = 100;

    private final Context mContext;
    private final List<Integer> mItems;
    private int mCurrentItemId = 0;

    public static class SimpleViewHolder extends RecyclerView.ViewHolder {
        public final TextView title;

        public SimpleViewHolder(View view) {
            super(view);
            title = (TextView) view.findViewById(R.id.title);
        }
    }

    public SimpleAdapter(Context context) {
        mContext = context;
        mItems = new ArrayList<Integer>(COUNT);
        for (int i = 0; i < COUNT; i++) {
            addItem(i);
        }
    }

    public SimpleViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        final View view = LayoutInflater.from(mContext).inflate(R.layout.item, parent, false);
        return new SimpleViewHolder(view);
    }

    @Override
    public void onBindViewHolder(SimpleViewHolder holder, final int position) {
        holder.title.setText(mItems.get(position).toString());
    }

    public void addItem(int position) {
        final int id = mCurrentItemId++;
        mItems.add(position, id);
        notifyItemInserted(position);
    }

    public void removeItem(int position) {
        mItems.remove(position);
        notifyItemRemoved(position);
    }

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

For the latest comments up here, I want to notify the comment I posted here: https://gist.github.com/gabrielemariotti/4c189fb1124df4556058#gistcomment-1706849

How do I adapt to the head in an image is also displayed?

Thanks for the gist, Gabriele, pretty useful! 👍

Kotlin version: https://gist.github.com/ppamorim/1f18448c1441716f8ab15b9ad2e8874e

Same comment than @lawrence651, The width of each item doesn't seem to match parent, even if I put with="match_parent" in each row layout!

How can we perform search in this adapter ?

When i replace TextView with ImageView in item.xml. It automatically adds very large margin at the top and bottom of each element that I can't change. Any clues

Found the solution. Needed to set ImageView's android:adjustViewBounds="true"

how to scrollToPosition(position) with RecyclerView thanks

I think there's something wrong with item decoration

Hi, thanks for helping us ....... !!
With this same code, how to implement using CursorAdapter. Please need help.

How to add a section later on and update the view, like using the notifyDataSetChanged() way

Nice, thanks a lot.

I wonder how this can work. In SectionedGridRecyclerViewAdapter's onBindViewHolder (line 87) the ViewHolder is explicitly cast to SectionViewHolder, but how can you be sure it is a SectionViewHolder? Since onCreateViewHolder creates instances of two different classes, onBindViewHolder is also going to get instances of two different classes as a parameter without regard to the position, right?
EDIT: Got it, it is ensured by the getItemViewType() method. Elegant!

When I tried to remove item from SimpleAdapter. I have an java.lang.IndexOutOfBoundsException. How can I remove an item and notify dataset successfully?

How to add more items with new headers ? I did several new sections.add(new SectionedGridRecyclerViewAdapter.Section(0,"Section x")) and also mSectionsAdapter.notifyDataSetChanged() , it didn't work. :(

how to change the section size at run time

Thanks...

my recyclerview adds blank space between items on scrolling, what might be the reason?

Its great and simple. Thanks man!

How do I make header sticky?

how to set onclikitem?

Check my answer: https://stackoverflow.com/a/61066643/2469427

Thanks! saved my day. :)

Nice thank you

still working in 2022, now I'll see if I can adapt this layout to what I want to do in my app

Great solution, works fine also with Xamarin.Android