手把手教你给RecycleView添加头布局和尾布局

RecycleView想必大家都不陌生，它已他的高拓展性取代了传统布局显示，同时配合协调布局，可以实现很多意想不到的酷炫交互，今天就和大家介绍一下，如何给RecycleView添加头布局和尾布局，同时你也可以通过自己的拓展实现更多复杂的布局。

首先我们先看一下效果：

实现头部尾部布局其实方法还是很多，这里我推荐使用Adapter设置itemType来做，那么问题来了，为什么这么做呢？因为拓展性更强，并且更加解耦。将逻辑都写在adapter中，比起写在activity中管理起来也更加方便。

首先，我们需要明确一点，什么是head，什么是foot,当位于第一个item的时候就是head,最后一个就是foot.之后我们根据不同的itemType加载出来就可以了。

第一步判断头尾部以及内容区域：

private int getBodySize() {
        return listData.size();
    }
    private boolean isHead(int position) {
        return headCount!=&&position<headCount;
    }
    private boolean isFoot(int position) {
        return footCount!=&&(position>=(getBodySize()+headCount));
    }
    public int getItemViewType(int position) {
        if (isHead(position)) {
            return HEAD_TYPE;
        }else if (isFoot(position)) {
            return FOOT_TYPE;
        }else {
            return BODY_TYPE;
        }
    }

根据不同的ViewType生产不同的Holder

@Override
    public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        switch (viewType) {
            case HEAD_TYPE:
                return new HeadViewHolder(mLayoutInflater.inflate(R.layout.trend_head,parent,false));
            case BODY_TYPE:
                return new BodyViewHolder(mLayoutInflater.inflate(R.layout.itemview_trend,parent,false));
            case FOOT_TYPE:
                return new FootViewHolder(mLayoutInflater.inflate(R.layout.trend_bottom,parent,false));
            default:
                return null;
        }

    }

拿到不同的holder生产具体实现：

@Override
    public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {
        if (holder instanceof HeadViewHolder) {

        }else if (holder instanceof BodyViewHolder) {
            ((BodyViewHolder) holder).body.setText((CharSequence) listData.get(position-headCount));

        }else if (holder instanceof FootViewHolder) {

        }

    }

怎么样是不是很简单？其实还可以拓展实现更多样式的item只需要我们设置itemtype和位置就可以了。最后附上完整代码。

public class HBRecycleViewAdapter<T> extends RecyclerView.Adapter<RecyclerView.ViewHolder>{
    private static final int HEAD_TYPE=;
    private static final int BODY_TYPE=;
    private static final int FOOT_TYPE=;
    private int headCount=;//头部个数，后续可以自己拓展
    private int footCount=;//尾部个数，后续可以自己拓展
    private LayoutInflater mLayoutInflater;
    private List<T>listData=new ArrayList<>();
    public HBRecycleViewAdapter(Context context,List<T>listData) {
        //this.context=context;
        mLayoutInflater=LayoutInflater.from(context);
        this.listData=listData;
    }
    private int getBodySize() {
        return listData.size();
    }
    private boolean isHead(int position) {
        return headCount!=&&position<headCount;
    }
    private boolean isFoot(int position) {
        return footCount!=&&(position>=(getBodySize()+headCount));
    }
    @Override
    public int getItemViewType(int position) {
        if (isHead(position)) {
            return HEAD_TYPE;
        }else if (isFoot(position)) {
            return FOOT_TYPE;
        }else {
            return BODY_TYPE;
        }
    }

    @Override
    public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        switch (viewType) {
            case HEAD_TYPE:
                return new HeadViewHolder(mLayoutInflater.inflate(R.layout.trend_head,parent,false));
            case BODY_TYPE:
                return new BodyViewHolder(mLayoutInflater.inflate(R.layout.itemview_trend,parent,false));
            case FOOT_TYPE:
                return new FootViewHolder(mLayoutInflater.inflate(R.layout.trend_bottom,parent,false));
            default:
                return null;
        }

    }

    @Override
    public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {
        if (holder instanceof HeadViewHolder) {

        }else if (holder instanceof BodyViewHolder) {
            ((BodyViewHolder) holder).body.setText((CharSequence) listData.get(position-headCount));

        }else if (holder instanceof FootViewHolder) {

        }

    }

    @Override
    public int getItemCount() {
        return headCount+getBodySize()+footCount;
    }
    private static class HeadViewHolder extends RecyclerView.ViewHolder{

        public HeadViewHolder(View itemView) {
            super(itemView);
        }
    }
    private static class BodyViewHolder extends RecyclerView.ViewHolder{
        TextView body;
        public BodyViewHolder(View itemView) {
            super(itemView);
            body= (TextView) itemView.findViewById(R.id.tv_body);
        }
    }
    private static class FootViewHolder extends RecyclerView.ViewHolder {

        public FootViewHolder(View itemView) {
            super(itemView);
        }
    }
}