高性能的给RecyclerView加上HeaderView和FooterView
程序员文章站
2022-06-16 08:42:32
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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。
第一篇鸿翔大神的文章
1，大神是把header和footer直接以View的形式引用的
private SparseArrayCompat<View> mHeaderViews = new SparseArrayCompat<>();
private SparseArrayCompat<View> 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<ViewHolder> getScrapHeapForType(int viewType) {
ArrayList<ViewHolder> scrap = mScrap.get(viewType);
if (scrap == null) {
scrap = new ArrayList<ViewHolder>();
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<RecyclerView.ViewHolder> {
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<DataBean> mHeaders = new ArrayList<>();
private ArrayList<DataBean> mFooters = new ArrayList<>();
private ArrayList<DataBean> 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<Map<String, Integer>> 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<String, Integer> 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。