Adding header view to recyclerview with gridlayout manager

Adding header view to recyclerview with gridlayout manager

Android Adding header view to recyclerview with gridlayout manager:

To add a header to a recyclerview with a gridlayout, first the adapter needs to be told that the header view is the first position - rather than the standard cell used for the content. Next, the layout manager must be told that the first position should have a span equal to the *span count of the entire list. 

Take a regular RecyclerView.Adapter class and configure it as follows:

	public class HeaderAdapter extends RecyclerView.Adapter<RecyclerView.ViewHolder> {
	private static final int ITEM_VIEW_TYPE_HEADER = 0;
	private static final int ITEM_VIEW_TYPE_ITEM = 1;
	private List<YourModel> mModelList;
	public HeaderAdapter (List<YourModel> modelList) {
	mModelList = modelList;
	}
	public boolean isHeader(int position) {
	return position == 0;
	}
	@Override
	public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
	LayoutInflater inflater = LayoutInflater.from(parent.getContext());
	if (viewType == ITEM_VIEW_TYPE_HEADER) {
	View headerView = inflater.inflate(R.layout.header, parent, false);
	return new HeaderHolder(headerView);
	}
	View cellView = inflater.inflate(R.layout.gridcell, parent, false);
	return new ModelHolder(cellView);
	}
	@Override
	public int getItemViewType(int position) {
	return isHeader(position) ? ITEM_VIEW_TYPE_HEADER : ITEM_VIEW_TYPE_ITEM;
	}
	@Override
	public void onBindViewHolder(RecyclerView.ViewHolder h, int position) {
	if (isHeader(position)) {
	return;
	}
	final YourModel model = mModelList.get(position -1 ); // Subtract 1 for header
	ModelHolder holder = (ModelHolder) h;
	// populate your holder with data from your model as usual
	}
	@Override
	GoalKicker.com – Android™ Notes for Professionals 142
	public int getItemCount() {
	return _categories.size() + 1; // add one for the header
	}
	}
	Then in the activity/fragment:
	final HeaderAdapter adapter = new HeaderAdapter (mModelList);
	final GridLayoutManager manager = new GridLayoutManager();
	manager.setSpanSizeLookup(new GridLayoutManager.SpanSizeLookup() {
	@Override
	public int getSpanSize(int position) {
	return adapter.isHeader(position) ? manager.getSpanCount() : 1;
	}
	});
	mRecyclerView.setLayoutManager(manager);
	mRecyclerView.setAdapter(adapter);

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The same approach can be used add a footer in addition to or instead of a header.