sticky-headers-recyclerview

This decorator allows you to easily create section headers for RecyclerViews using a LinearLayoutManager in either vertical or horizontal orientation.

Credit to Emil Sjölander for creating StickyListHeaders, a library that many of us relied on for sticky headers in our listviews.

Here is a quick video of it in action (click to see the full video):

Download

Current version:

compile 'com.timehop.stickyheadersrecyclerview:library:[latest.version.number]@aar'

Usage

There are three main classes, StickyRecyclerHeadersAdapter, StickyRecyclerHeadersDecoration, and StickyRecyclerHeadersTouchListener.

StickyRecyclerHeadersAdapter has a very similar interface to the RecyclerView.Adapter, and it is recommended that you make your RecyclerView.Adapter implement StickyRecyclerHeadersAdapter.

There interface looks like this:

public interface StickyRecyclerHeadersAdapter<VH extends RecyclerView.ViewHolder> {
  public long getHeaderId(int position);

  public VH onCreateHeaderViewHolder(ViewGroup parent);

  public void onBindHeaderViewHolder(VH holder, int position);

  public int getItemCount();
}

The second class, StickyRecyclerHeadersDecoration, is where most of the magic happens, and does not require any configuration on your end. Here's an example from onCreate() in an activity:

mRecyclerView = (RecyclerView) findViewById(R.id.recyclerview);
mAdapter = new MyStickyRecyclerHeadersAdapter();
mRecyclerView.setAdapter(mAdapter);
mRecyclerView.setLayoutManager(new LinearLayoutManager(context));
mRecyclerView.addItemDecoration(new StickyRecyclerHeadersDecoration(mAdapter));

StickyRecyclerHeadersTouchListener allows you to listen for clicks on header views. Simply create an instance of StickyRecyclerHeadersTouchListener, set the OnHeaderClickListener, and add the StickyRecyclerHeadersTouchListener as a touch listener to your RecyclerView.

StickyRecyclerHeadersTouchListener touchListener =
    new StickyRecyclerHeadersTouchListener(recyclerView, headersDecor);
touchListener.setOnHeaderClickListener(
    new StickyRecyclerHeadersTouchListener.OnHeaderClickListener() {
      @Override
      public void onHeaderClick(View header, int position, long headerId) {
        Toast.makeText(MainActivity.this, "Header position: " + position + ", id: " + headerId,
            Toast.LENGTH_SHORT).show();
      }
    });
mRecyclerView.addOnItemTouchListener(touchListener);

The StickyHeaders aren't aware of your adapter so if you must notify them when your data set changes.

    mAdapter.registerAdapterDataObserver(new RecyclerView.AdapterDataObserver() {
      @Override public void onChanged() {
        headersDecor.invalidateHeaders();
      }
    });

If the Recyclerview's layout manager implements getExtraLayoutSpace (to preload more content then is visible for performance reasons), you must implement ItemVisibilityAdapter and pass an instance as a second argument to StickyRecyclerHeadersDecoration's constructor.

    @Override
    public boolean isPositionVisible(final int position) {
        return layoutManager.findFirstVisibleItemPosition() <= position
            && layoutManager.findLastVisibleItemPosition() >= position;
    }

Item animators don't play nicely with RecyclerView decorations, so your mileage with that may vary.

Compatibility

API 11+

Known Issues

The header views aren't recycled at this time. Contributions are most welcome.
I haven't tested this with ItemAnimators yet.
The header views are drawn to a canvas, and are not actually a part of the view hierarchy. As such, they can't have touch states, and you may run into issues if you try to load images into them asynchronously.

Version History

0.4.3 (12/24/2015) - Change minSDK to 11, fix issue with header bounds caching

0.4.2 (8/21/2015) - Add support for reverse ReverseLayout in LinearLayoutManager by AntonPukhonin

0.4.1 (6/24/2015) - Fix "dancing headers" by DarkJaguar91

0.4.0 (4/16/2015) - Code reorganization by danoz73, fixes for different sized headers, performance improvements

0.3.6 (1/30/2015) - Prevent header clicks from passing on the touch event

0.3.5 (12/12/2014) - Add StickyRecyclerHeadersDecoration.invalidateHeaders() method

0.3.4 (12/3/2014) - Fix issues with rendering of header views with header ID = 0

0.3.3 (11/13/2014) - Fixes for padding, support views without headers

0.3.2 (11/1/2014) - Bug fixes for list items with margins and deleting items

0.2 (10/3/2014) - Add StickyRecyclerHeadersTouchListener