RecyclerView添加Header和Footer

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

这里写图片描述

这里写图片描述

RecyclerView实现添加HeaderView和FooterView的核心就是在Adapter里面的onCreateViewHolder根据viewType来判断是列表项还是HeaderView来分别加载不同的布局文件，当然viewType的判断规则也是由我们定义的，废话不多说，看一下具体的实现效果。
1：Gradle配置 build.gradle

compile 'com.android.support:recyclerview-v7:23.1.1'
compile 'com.android.support:cardview-v7:23.1.1'

2：主布局文件 activity_main.xml 很简单里面一个RecyclerView

3：列表项布局 rv_item.xml 外面一个CardView的卡片式容器里面一个TextView

4：列表头部布局 rv_header.xml

5：列表底部布局 rv_footer.xml

*6：HeaderBottomAdapter.java，RecyclerView的Adapter，在getItemViewType方法里面判断了当前Item的类型，然后在onCreateViewHolder跟据item的类型分别加载不同的布局以实现HeaderView和FooterView，其他方法的含义可以参考注释
**

public class HeaderBottomAdapter extends RecyclerView.Adapter {

//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 == ITEM_TYPE_CONTENT) {
        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;
}

}

7：最后一步，MainActivity.java

public class MainActivity extends AppCompatActivity {
private RecyclerView mRecyclerView;
private HeaderBottomAdapter adapter;
GridLayoutManager gridLayoutManager;
LinearLayoutManager layoutManager;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    mRecyclerView=(RecyclerView)findViewById(R.id.rv_list);
    //List布局
    layoutManager=new LinearLayoutManager(this);
    layoutManager.setOrientation(LinearLayoutManager.VERTICAL);
    mRecyclerView.setLayoutManager(layoutManager);
    mRecyclerView.setAdapter(adapter=new HeaderBottomAdapter(this));

    //Grid布局 
//        gridLayoutManager=new GridLayoutManager(MainActivity.this, 2);
//        mRecyclerView.setLayoutManager(gridLayoutManager);//这里用线性宫格显示 类似于grid view
//        mRecyclerView.setAdapter(adapter=new HeaderBottomAdapter(this));
//
//
//            gridLayoutManager.setSpanSizeLookup(new GridLayoutManager.SpanSizeLookup() {
//                @Override
//                public int getSpanSize(int position) {
//                    return (adapter.isHeaderView(position) || adapter.isBottomView(position)) ? gridLayoutManager.getSpanCount() : 1;
//                }
//            });


    }

}

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;
            }
       });