使用RecyclerView添加Header和Footer的方法

RecyclerView虽然作为ListView的替代者有着较好的性能提升,但是ListView的一些常用功能却没有提供,比如我们平时会经常用到的addHeaderView,addFooterView,既然RecyclerView没有提供这个方法,我们应该如何为列表添加头部和底部呢?通过看ListView的源码可以知道ListView的添加Header和Footer是靠Adapter里面动态添加的,所以我们按照这个思路也给RecyclerView添加HeaderView和FooterView,先看一下效果:


import android.content.Context;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;

/**
 * Created by Lijizhou on 2016/2/24.
 * Blog:http://blog.csdn.net/leejizhou
 * QQ:3107777777
 */
public class HeaderBottomAdapter extends RecyclerView.Adapter<RecyclerView.ViewHolder> {
    //item类型
    public static final int ITEM_TYPE_HEADER = 0;
    public static final int ITEM_TYPE_CONTENT = 1;
    public static final int ITEM_TYPE_BOTTOM = 2;
    //模拟数据
    public String[] texts = {"java", "python", "C++", "Php", ".NET", "js", "Ruby", "Swift", "OC"};
    private LayoutInflater mLayoutInflater;
    private Context mContext;
    private int mHeaderCount = 1;//头部View个数
    private int mBottomCount = 1;//底部View个数

    public HeaderBottomAdapter(Context context) {
        mContext = context;
        mLayoutInflater = LayoutInflater.from(context);
    }

    //内容长度
    public int getContentItemCount() {
        return texts.length;
    }

    //判断当前item是否是HeadView
    public boolean isHeaderView(int position) {
        return mHeaderCount != 0 && position < mHeaderCount;
    }

    //判断当前item是否是FooterView
    public boolean isBottomView(int position) {
        return mBottomCount != 0 && position >= (mHeaderCount + getContentItemCount());
    }

    //判断当前item类型
    @Override
    public int getItemViewType(int position) {
        int dataItemCount = getContentItemCount();
        if (mHeaderCount != 0 && position < mHeaderCount) {
//头部View
            return ITEM_TYPE_HEADER;
        } else if (mBottomCount != 0 && position >= (mHeaderCount + dataItemCount)) {
//底部View
            return ITEM_TYPE_BOTTOM;
        } else {
//内容View
            return ITEM_TYPE_CONTENT;
        }
    }

    //内容 ViewHolder
    public static class ContentViewHolder extends RecyclerView.ViewHolder {
        private TextView textView;

        public ContentViewHolder(View itemView) {
            super(itemView);
            textView = (TextView) itemView.findViewById(R.id.tv_item_text);
        }
    }

    //头部 ViewHolder
    public static class HeaderViewHolder extends RecyclerView.ViewHolder {
        public HeaderViewHolder(View itemView) {
            super(itemView);
        }
    }

    //底部 ViewHolder
    public static class BottomViewHolder extends RecyclerView.ViewHolder {
        public BottomViewHolder(View itemView) {
            super(itemView);
        }
    }

    @Override
    public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        if (viewType == ITEM_TYPE_HEADER) {
            return new HeaderViewHolder(mLayoutInflater.inflate(R.layout.rv_header, parent, false));
        } else if (viewType == mHeaderCount) {
            return new ContentViewHolder(mLayoutInflater.inflate(R.layout.rv_item, parent, false));
        } else if (viewType == ITEM_TYPE_BOTTOM) {
            return new BottomViewHolder(mLayoutInflater.inflate(R.layout.rv_footer, parent, false));
        }
        return null;
    }

    @Override
    public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {
        if (holder instanceof HeaderViewHolder) {
        } else if (holder instanceof ContentViewHolder) {
            ((ContentViewHolder) holder).textView.setText(texts[position - mHeaderCount]);
        } else if (holder instanceof BottomViewHolder) {
        }
    }

    @Override
    public int getItemCount() {
        return mHeaderCount + getContentItemCount() + mBottomCount;
    }
}

这里注意一点,如果你的RecyclerView使用Grid类型列表在设置Adapter后需要调用这个方法,根据当前Item类型来判断占据的横向格数,这也是Adapter里面实现isHeaderView和isBottomView的缘故

gridLayoutManager.setSpanSizeLookup(new GridLayoutManager.SpanSizeLookup() {
        @Override
        public int getSpanSize(int position) {
            return (adapter.isHeaderView(position) || adapter.isBottomView(position)) ? gridLayoutManager.getSpanCount() : 1;
        }
    });

Ok,RecyclerView添加Header和Footer就这样轻松实现了,你也可以把Adapter再次封装更有利于日常的开发。

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