RecyclerView的使用（3）之添加Header和Footer

原创文章，转载请注明 http://blog.csdn.net/leejizhou/article/details/50742544 李济洲的博客

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

如果你还不了解RecyclerView如何使用，可以看一下前几篇博文
RecyclerView的使用（1）之HelloWorld
RecyclerView的使用（2）之多Item布局的加载

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

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="match_parent">
    <android.support.v7.widget.RecyclerView  xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="match_parent" android:id="@+id/rv_list" />
</LinearLayout>

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

<?xml version="1.0" encoding="utf-8"?>
<android.support.v7.widget.CardView  xmlns:card_view="http://schemas.android.com/apk/res-auto" xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="wrap_content" android:layout_margin="8dp" android:id="@+id/cv_item" android:foreground="?android:attr/selectableItemBackground" card_view:cardCornerRadius="4dp" card_view:cardElevation="4dp" >
    <LinearLayout  android:layout_width="match_parent" android:layout_height="wrap_content">
        <TextView  android:layout_width="wrap_content" android:layout_height="wrap_content" android:id="@+id/tv_item_text" android:text="test" android:layout_margin="8dp" />
    </LinearLayout>

</android.support.v7.widget.CardView>

4：列表头部布局 rv_header.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.v7.widget.CardView  xmlns:card_view="http://schemas.android.com/apk/res-auto" xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="wrap_content" android:layout_margin="8dp" android:id="@+id/cv_item" android:foreground="?android:attr/selectableItemBackground" card_view:cardCornerRadius="4dp" card_view:cardElevation="4dp" card_view:cardBackgroundColor="#4CAF50" >
    <LinearLayout  android:layout_width="match_parent" android:layout_height="150dp" >
        <TextView  android:layout_width="match_parent" android:layout_height="match_parent" android:text="Header" android:textSize="30sp" android:textColor="#ffffff" android:gravity="center" />
    </LinearLayout>
</android.support.v7.widget.CardView>

5：列表底部布局 rv_footer.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.v7.widget.CardView  xmlns:card_view="http://schemas.android.com/apk/res-auto" xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="wrap_content" android:layout_margin="8dp" android:id="@+id/cv_item" android:foreground="?android:attr/selectableItemBackground" card_view:cardCornerRadius="4dp" card_view:cardElevation="4dp" card_view:cardBackgroundColor="#E91E63" >
    <LinearLayout  android:layout_width="match_parent" android:layout_height="150dp" >
        <TextView  android:layout_width="match_parent" android:layout_height="match_parent" android:text="Footer" android:textSize="30sp" android:textColor="#ffffff" android:gravity="center" />

    </LinearLayout>
</android.support.v7.widget.CardView>

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

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;
    }



}

7：最后一步，MainActivity.java

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.support.v7.widget.GridLayoutManager;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;

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;
                }
           });

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，本篇博文的源码下载地址 下载地址