public class NormalAdapter  extends RecyclerView.Adapter<NormalAdapter.InnerHolder> implements StickHeaderDecoration.StickHeaderInterface{NormalAdapter(Activity activity, List<String> dates){this.activity = activity;this.dates = dates;}@Overridepublic boolean isStick(int position) {return position % 6 == 0;}Activity activity;private List<String> dates;@Overridepublic InnerHolder onCreateViewHolder(ViewGroup parent, int viewType) {View inflate = LayoutInflater.from(activity).inflate(R.layout.item, parent,false);return new InnerHolder(inflate);}@Overridepublic void onBindViewHolder(InnerHolder holder, int position) {if(isStick(position)){holder.itemView.setBackgroundResource(R.color.colorAccent);holder.tvText.setText(position / 6 +"");}else{holder.itemView.setBackgroundResource(R.color.white);holder.tvText.setText(dates.get(position));}}@Overridepublic int getItemCount() {return dates.size();}class InnerHolder extends RecyclerView.ViewHolder{TextView tvText;public InnerHolder(View itemView) {super(itemView);tvText = (TextView) itemView.findViewById(R.id.tvText);}}
}

public class MainActivity extends Activity {private RecyclerView recycle;private List<String> dates = new ArrayList<>();@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);recycle = (RecyclerView) findViewById(R.id.recycle);for(int i=0;i<66;i++){dates.add("date : "+i);}recycle.setLayoutManager(new LinearLayoutManager(this));recycle.setAdapter(new NormalAdapter(this, dates));recycle.addItemDecoration(new StickHeaderDecoration(recycle));}}

public class StickHeaderDecoration extends RecyclerView.ItemDecoration {public interface StickHeaderInterface {/*** is this item need stick* @param position now item position in the recyclerView* @return true : need stick else not*/boolean isStick(int position);}private RecyclerView recyclerView;private RecyclerView.LayoutManager manager;private RecyclerView.Adapter adapter;private StickHeaderInterface stickHeaderInterface;/*** 进行一些容错检查*/public StickHeaderDecoration(RecyclerView recyclerView) {this.recyclerView = recyclerView;this.manager = recyclerView.getLayoutManager();this.adapter = recyclerView.getAdapter();if (adapter == null) {throw new RuntimeException("please set Decoration after set adapter");}if (adapter instanceof StickHeaderInterface) {stickHeaderInterface = (StickHeaderInterface) adapter;return;}throw new RuntimeException("please make your adapter implements StickHeaderInterface");}/*** 绘制头部的stick view*/@Overridepublic void onDrawOver(Canvas c, RecyclerView parent, RecyclerView.State state) {super.onDrawOver(c, parent, state);View childAt = parent.getChildAt(0);if (childAt == null)return;RecyclerView.ViewHolder childViewHolder = parent.getChildViewHolder(childAt);int position = childViewHolder.getPosition();for (int i = position; i >= 0; i--) {if (stickHeaderInterface.isStick(i)) {int top = 0;if (position + 1 < adapter.getItemCount()) {if (stickHeaderInterface.isStick(position + 1)) {View childNext = parent.getChildAt(1);top = manager.getDecoratedTop(childNext) < 0 ? 0 : manager.getDecoratedTop(childNext);}}RecyclerView.ViewHolder inflate = recyclerView.getAdapter().createViewHolder(parent,recyclerView.getAdapter().getItemViewType(i));recyclerView.getAdapter().bindViewHolder(inflate, i);int measureHeight = getMeasureHeight(inflate.itemView);c.save();if (top < inflate.itemView.getMeasuredHeight() && top > 0) {c.translate(0, top - measureHeight);}inflate.itemView.draw(c);c.restore();return;}}}/*** 测量控件的高度** @param header*/private int getMeasureHeight(View header) {int widthSpec = View.MeasureSpec.makeMeasureSpec(recyclerView.getWidth(), View.MeasureSpec.EXACTLY);int heightSpec = View.MeasureSpec.makeMeasureSpec(0, View.MeasureSpec.UNSPECIFIED);header.measure(widthSpec, heightSpec);header.layout(0, 0, header.getMeasuredWidth(), header.getMeasuredHeight());return header.getMeasuredHeight();}
}