高性能的给RecyclerView加上HeaderView和FooterView

源码地址：https://github.com/bravinshi/AdvancedRecyclerView

自己写的是对于他人的改进，修复了若干问题。

建议阅读之前先读一下这两篇文章

1，http://blog.csdn.net/lmj623565791/article/details/51854533 

2，http://blog.csdn.net/zxt0601/article/details/52267325

在此先感谢上面两篇文章的作者，做IT，本来就是要互相学习嘛。

 

先说下二篇文章中的wrapper存在的问题。

第一篇鸿翔的文章

 

1，鸿翔是把header和footer直接以View的形式引用的

 

private SparseArrayCompat mHeaderViews = new SparseArrayCompat<>();
    private SparseArrayCompat mFootViews = new SparseArrayCompat<>();

 

 

 

并且添加View的时候，type是渐渐累加的

 

 

 

 

 public void addFootView(View view)
    {
        mFootViews.put(mFootViews.size() + BASE_ITEM_TYPE_FOOTER, view);
    }

 

这会导致什么情况呢，很简单，如果加上20个View作为Header，如果界面滑到底，首先内存中就确确实实存在20个Header不会被GC掉，因为引用还是在的。另外RecyclerView的缓存逻辑和ListView的缓存逻辑相似，它们都会给不同的Type开辟一个单独的ArrayList,源码如下

 

 

 

 

private ArrayList getScrapHeapForType(int viewType) {
            ArrayList scrap = mScrap.get(viewType);
            if (scrap == null) {
                scrap = new ArrayList();
                mScrap.put(viewType, scrap);
                if (mMaxScrap.indexOfKey(viewType) < 0) {
                    mMaxScrap.put(viewType, DEFAULT_MAX_SCRAP);
                }
            }
            return scrap;
        }

也就是说，对于一个Header来说mHeaderViews里面引用了一次，另外还创建了一个单独的缓存用ArrayList，而这个ArrayList里面只会放一个Holder，就是这个type对应的Holder。那么Holder是什么？Holder其实就是一个View，它在这里可以看成是Header的一个copy。那么如果有20个Header，那么内存里有20个Header，还要有20个ArrayList要存放他们的Holder，结果就是内存瞬间爆炸！！！

 

 

2

这里的mInnerAdapter是一个Adapter，而大神的wrapper本身也是继承了Adapter，这个看起来算是很奇怪的。而mInnerAdater在这个类里面是不会被设置为某个RecyclerView的adapter的，因为在使用的时候是把这个wrapper设置为RecyclerView的dapter的，这里面mInnerAdapter只是仅仅作为非headerView和footerView的数据的载体而已。那为什么不自己写一个ArrayList代替却用一个更重量的Adapter呢。

 

3，泛型没必要。

第二篇

 

1，首先还有和鸿翔大神一样的问题，就是mInnerAdater容器化，和它本身的设计意义不符，所以完全可以去掉。

 

2，作者为了让Header能够被GC掉而设置header的缓存数是0,首先能不能被GC是要打问号的，另外，如果Header足够大，跨多个屏幕，那么，把Header滑出界面后在滑回来，这个Header是要重新创建的，就算被GC掉了还要重新创建，那这就是典型的时间换空间，由于是不一定被GC掉，那么这买卖就算亏了啊。怒 (ノ｀ー´)ノ・・・~~┻━┻，这个和RecyclerView的设计初衷相违背，感觉没必要这么做。

 

3，Footer还是和鸿翔大神的一样，一个footer单独对应一个Type，这样内存爆炸的很快。

 

4，泛型没必要。

好了，客官们要问了，怎么改？

来来来，直接上代码

 

package com.yalantis.phoenix.wrapper;

import android.support.v7.widget.GridLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.support.v7.widget.StaggeredGridLayoutManager;
import android.view.ViewGroup;

import java.util.ArrayList;

/**
 * Created by shijianguo on 2017/8/25.
 */

public abstract class HeaderAndFooterWrapper extends RecyclerView.Adapter {

    private static final int BASE_ITEM_TYPE_FOOTER = 2000000;//footerView默认type
    private static final int BASE_ITEM_TYPE_HEADER = 1000000;// headerView默认type
    private static final int BASE_ITEM_TYPE_GENERAL= 0;// 一般view默认type 0也是android源码中的默认的type值

    private ArrayList mHeaders = new ArrayList<>();
    private ArrayList mFooters = new ArrayList<>();
    private ArrayList mGeneralData = new ArrayList<>();

    @Override
    public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        if (isHeaderType(viewType)){
            return onCreateHeaderViewHolder(parent,viewType);
        }else if(isFooterType(viewType)){
            return onCreateFooterViewHolder(parent,viewType);
        }
        return onCreateGeneralViewHolder(parent,viewType);
    }

    @Override
    public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {
        if (isHeaderViewPos(position)){
            onBindHeaderViewHolder(holder,position);
        }else if(isFooterViewPos(position)){
            onBindFooterViewHolder(holder,position - getHeaderViewCount() - getInnerItemCount());
        }else {
            onBindGeneralViewHolder(holder,position - getHeaderViewCount());
        }
    }



    public abstract RecyclerView.ViewHolder onCreateHeaderViewHolder(ViewGroup parent, int viewType);

    public abstract RecyclerView.ViewHolder onCreateFooterViewHolder(ViewGroup parent, int viewType);

    public abstract RecyclerView.ViewHolder onCreateGeneralViewHolder(ViewGroup parent, int viewType);

    public abstract void onBindHeaderViewHolder(RecyclerView.ViewHolder holder, int position);

    public abstract void onBindFooterViewHolder(RecyclerView.ViewHolder holder, int position);

    public abstract void onBindGeneralViewHolder(RecyclerView.ViewHolder holder, int position);

    @Override
    public int getItemCount() {
        return getInnerItemCount() + getHeaderViewCount() + getFooterViewCount();
    }

    public int getHeaderViewCount() {
        return mHeaders.size();
    }

    public int getFooterViewCount() {
        return mFooters.size();
    }

    private int getInnerItemCount() {
        return mGeneralData.size();
    }

    private boolean isHeaderViewPos(int position) {
        return getHeaderViewCount() > position;
    }

    private boolean isFooterViewPos(int position) {
        return position >= getHeaderViewCount() + getInnerItemCount();
    }

    private boolean isHeaderType(int type){
        if (mHeaders.size() > 0){
            for (DataBean bean : mHeaders){
                if(bean.getType() == type){
                    return true;
                }
            }
        }
        return false;
    }

    private boolean isFooterType(int type){
        if (mFooters.size() > 0){
            for (DataBean bean : mFooters){
                if(bean.getType() == type){
                    return true;
                }
            }
        }
        return false;
    }

    @Override
    public int getItemViewType(int position) {
        if (isHeaderViewPos(position)) {
            return mHeaders.get(position).getType();
        } else if (isFooterViewPos(position)) {
            return mFooters.get(position - getHeaderViewCount() - getInnerItemCount()).getType();
        }
        return mGeneralData.get(position - getHeaderViewCount()).getType();
    }

    public void addHeader(Object data){
        addHeader(data,BASE_ITEM_TYPE_HEADER);
    }

    public void addHeader(Object data,int type){
        mHeaders.add(new DataBean(data,type));
    }

    public void addFooter(Object data){
        addFooter(data,BASE_ITEM_TYPE_FOOTER);
    }

    public void addFooter(Object data,int type){
        mFooters.add(new DataBean(data,type));
    }

    public void addGeneral(Object data){
        addGeneral(data,BASE_ITEM_TYPE_GENERAL);
    }

    public void addGeneral(Object data,int type){
        mGeneralData.add(new DataBean(data,type));
    }

    private class DataBean {
        private Object data;
        private int type;

        private DataBean(Object data, int type){
            super();
            this.data = data;
            this.type = type;
        }

        public Object getData() {
            return data;
        }

        public void setData(Object data) {
            this.data = data;
        }

        public int getType() {
            return type;
        }

        public void setType(int type) {
            this.type = type;
        }
    }

    @Override
    public void onAttachedToRecyclerView(RecyclerView recyclerView) {
        super.onAttachedToRecyclerView(recyclerView);
        //为了兼容GridLayout
        RecyclerView.LayoutManager layoutManager = recyclerView.getLayoutManager();
        if (layoutManager instanceof GridLayoutManager) {
            final GridLayoutManager gridLayoutManager = (GridLayoutManager) layoutManager;
            final GridLayoutManager.SpanSizeLookup spanSizeLookup = gridLayoutManager.getSpanSizeLookup();

            gridLayoutManager.setSpanSizeLookup(new GridLayoutManager.SpanSizeLookup() {
                @Override
                public int getSpanSize(int position) {
                    if (isHeaderViewPos(position)) {
                        return gridLayoutManager.getSpanCount();
                    } else if (isFooterViewPos(position)) {
                        return gridLayoutManager.getSpanCount();
                    }
                    if (spanSizeLookup != null)
                        return spanSizeLookup.getSpanSize(position);
                    return 1;
                }
            });
            gridLayoutManager.setSpanCount(gridLayoutManager.getSpanCount());
        }

    }

    @Override
    public void onViewAttachedToWindow(RecyclerView.ViewHolder holder) {
        super.onViewAttachedToWindow(holder);
        int position = holder.getLayoutPosition();
        if (isHeaderViewPos(position) || isFooterViewPos(position)) {
            ViewGroup.LayoutParams lp = holder.itemView.getLayoutParams();

            if (lp != null
                    && lp instanceof StaggeredGridLayoutManager.LayoutParams) {

                StaggeredGridLayoutManager.LayoutParams p =
                        (StaggeredGridLayoutManager.LayoutParams) lp;

                p.setFullSpan(true);
            }
        }
    }
}

首先说下DataBean存在的意义，DataBean是把数据本身和type做了分离，这样type由coder本身定义，不和数据本身有强绑定。

 

 

innerAdapter被一个ArrayList替代，这样降低了内存开销，Header和Footer也是ArrayList，这样data和view解耦。

 

说一下我尝试添加泛型时遇见的一个问题。我尝试添加三个泛型对应HeaderViewHolder，FooterViewHolder和中间的view用到的GeneralViewHolder，但是由于系统本身的Adapter泛型只能添加一个ViewHoler，另外这个泛型是onCreateViewHoler的返回类型。header和footer的viewholer都是也要用这个方法创建的，这样导致单独添加HeaderViewHolder和FooterViewHolder没有意义（没法返回啊），那只好返回RecyvlerView.ViewHolder，coder在用的时候只需要自己强转就好。

 

说下怎么用，非常简单的好么。直接上代码

 

 

package com.yalantis.phoenix.sample;

import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.GridLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.TextView;

import com.yalantis.phoenix.AdvancedRecyclerView;
import com.yalantis.phoenix.viewholder.MyViewHolder;
import com.yalantis.phoenix.wrapper.HeaderAndFooterWrapper;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

/**
 * Created by shijianguo on 2017/8/18.
 */

public class AdvancedRecyclerActivity extends AppCompatActivity {

    public static final String KEY_ICON = "icon";
    public static final String KEY_COLOR = "color";

    protected List> mSampleList;

    private AdvancedRecyclerView mRecyclerView;
    private MyHeaderAndFooterWrapper myAdapter;

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_recycler_view);
        myAdapter = new MyHeaderAndFooterWrapper();
        myAdapter.addHeader(0);
        myAdapter.addHeader(0);
        myAdapter.addHeader(0);
        myAdapter.addHeader(0);
        myAdapter.addHeader(0);
        myAdapter.addHeader(0);
        myAdapter.addHeader(0);
        myAdapter.addHeader(0);
        myAdapter.addHeader(0);
        myAdapter.addHeader(0);
        myAdapter.addHeader(0);
        myAdapter.addFooter(0);
        myAdapter.addFooter(0);
        myAdapter.addFooter(0);
        myAdapter.addFooter(0);
        myAdapter.addFooter(0);
        myAdapter.addFooter(0);
        myAdapter.addFooter(0);
        myAdapter.addFooter(0);
        myAdapter.addFooter(0);
        myAdapter.addFooter(0);
        myAdapter.addGeneral(0);
        myAdapter.addGeneral(0);
        myAdapter.addGeneral(0);
        myAdapter.addGeneral(0);
        myAdapter.addGeneral(0);
        myAdapter.addGeneral(0);
        myAdapter.addGeneral(0);
        myAdapter.addGeneral(0);
        myAdapter.addGeneral(0);
        myAdapter.addGeneral(0);

        Map map;
        mSampleList = new ArrayList<>();

        int[] icons = {
                R.drawable.icon_1,
                R.drawable.icon_2,
                R.drawable.icon_3};

        int[] colors = {
                R.color.saffron,
                R.color.eggplant,
                R.color.sienna};

        for (int i = 0; i < 5; i++) {
            map = new HashMap<>();
            map.put(KEY_ICON, icons[i%3]);
            map.put(KEY_COLOR, colors[i%3]);
            mSampleList.add(map);
        }

        mRecyclerView = (AdvancedRecyclerView) findViewById(R.id.recycler_view);
        mRecyclerView.setLayoutManager(new GridLayoutManager(this,2));
        mRecyclerView.setAdapter(myAdapter);
    }

    class MyHeaderAndFooterWrapper extends HeaderAndFooterWrapper{

        @Override
        public MyViewHolder onCreateHeaderViewHolder(ViewGroup parent, int viewType) {
            TextView  view = new TextView(parent.getContext());
            view.setLayoutParams(new RecyclerView.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT,400));
            return MyViewHolder.createViewHolder(parent.getContext(),view);
        }

        @Override
        public MyViewHolder onCreateFooterViewHolder(ViewGroup parent, int viewType) {
            TextView  view = new TextView(parent.getContext());
            view.setLayoutParams(new RecyclerView.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT,400));
            return MyViewHolder.createViewHolder(parent.getContext(),view);
        }

        @Override
        public RecyclerView.ViewHolder onCreateGeneralViewHolder(ViewGroup parent, int viewType) {
            return new MyViewHolder1(LayoutInflater.from(
                    AdvancedRecyclerActivity.this).inflate(R.layout.list_item, parent,
                    false));
        }

        @Override
        public void onBindHeaderViewHolder(RecyclerView.ViewHolder holder, int position) {
            ((TextView)holder.itemView).setText("这是一个Header");
        }

        @Override
        public void onBindFooterViewHolder(RecyclerView.ViewHolder holder, int position) {
            ((TextView)holder.itemView).setText("这是一个Footer");
        }

        @Override
        public void onBindGeneralViewHolder(RecyclerView.ViewHolder holder, int position) {
            ((MyViewHolder1)holder).imageViewIcon.setImageResource(mSampleList.get(position % 3).get(KEY_ICON));
            ((MyViewHolder1)holder).itemView.setBackgroundResource(mSampleList.get(position % 3).get(KEY_COLOR));
        }
    }

    class MyViewHolder1 extends RecyclerView.ViewHolder
    {
        ImageView imageViewIcon;

        MyViewHolder1(View view)
        {
            super(view);
            imageViewIcon = (ImageView) view.findViewById(R.id.image_view_icon);
        }
    }
}

 

 

 

 

 

点此获取源码，把simple中的配置文件中的Activity入口改为AdvancedRecyclerActivity即可

,有问题欢迎留言交流。