RecyclerView的使用（3）之加入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尽管作为ListView的替代者有着较好的性能提升。可是ListView的一些经常使用功能却没有提供，比方我们平时会经经常使用到的addHeaderView，addFooterView，既然RecyclerView没有提供这种方法，我们应该怎样为列表加入头部和底部呢？通过看ListView的源代码能够知道ListView的加入Header和Footer是靠Adapter里面动态加入的。所以我们依照这个思路也给RecyclerView加入HeaderView和FooterView。先看一下效果

假设你还不了解RecyclerView怎样使用。能够看一下前几篇博文

RecyclerView的使用（1）之HelloWorld

RecyclerView的使用（2）之多Item布局的载入

RecyclerView实现加入HeaderView和FooterView的核心就是在Adapter里面的onCreateViewHolder依据viewType来推断是列表项还是HeaderView来分别载入不同的布局文件。当然viewType的推断规则也是由我们定义的。废话不多说，看一下详细的实现效果。

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 非常easy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方法里面推断了当前Item的类型。然后在onCreateViewHolder跟据item的类型分别载入不同的布局以实现HeaderView和FooterView，其它方法的含义能够參考凝视

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;

    }

    //推断当前item是否是HeadView

    public boolean isHeaderView(int position) {

        return mHeaderCount != 0 && position < mHeaderCount;

    }

    //推断当前item是否是FooterView

    public boolean isBottomView(int position) {

        return mBottomCount != 0 && position >= (mHeaderCount + getContentItemCount());

    }

    //推断当前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

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 相似于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。假设你的RecyclerView使用Grid类型列表在设置Adapter后须要调用这种方法，依据当前Item类型来推断占领的横向格数，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加入Header和Footer就这样轻松实现了，你也能够把Adapter再次封装更有利于日常的开发，本篇博文的源代码下载地址 下载地址

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