本文参考：
http://blog.csdn.net/u014315849/article/details/52537700
http://blog.csdn.net/lmj623565791/article/details/45059587
http://blog.csdn.net/lmj623565791/article/details/51118836
Recycleview设置：
1.setLayoutManager() //设置布局管理器
2.setAdapter() //设置适配器
3.addItemDecoration() //添加装饰（如分割线）
4.setItemAnimator() //设置动画（如添加、删除动画）
RecyclerView.LayoutManager是一个抽象类
实现类：
1.LinearLayoutManager 线性管理器，支持横向、纵向。
2.GridLayoutManager 网格布局管理器
3.StaggeredGridLayoutManager 瀑布流式布局管理器
ViewHolder
ViewHolder是google在优化ListView性能的技巧上就提到的，虽然google并没有强制使用，但事实上它已经成为ListView的编写规范。在RecyclerView上,ViewHolder的使用成为了一种强制手段了。
首先来看看ViewHolder的用法，这是一个简单的获取String数组并展现到TextView上。通过数组的大小来创建item的数量。
public class MyAdapter extends RecyclerView.Adapter<MyAdapter.ViewHolder> {
public String[] datas = null;
public MyAdapter(String[] datas) {
this.datas = datas;
}
//创建新View，被LayoutManager所调用
@Override
public ViewHolder onCreateViewHolder(ViewGroup viewGroup, int viewType) {
View view = LayoutInflater.from(viewGroup.getContext()).inflate(R.layout.item,viewGroup,false);
ViewHolder vh = new ViewHolder(view);
return vh;
}
//将数据与界面进行绑定的操作
@Override
public void onBindViewHolder(ViewHolder viewHolder, int position) {
viewHolder.mTextView.setText(datas[position]);
}
//获取数据的数量
@Override
public int getItemCount() {
return datas.length;
}
//自定义的ViewHolder，持有每个Item的的所有界面元素
public static class ViewHolder extends RecyclerView.ViewHolder {
public TextView mTextView;
public ViewHolder(View view){
super(view);
mTextView = (TextView) view.findViewById(R.id.text);
}
}
}
介绍完RecycleView和ViewHolder，接下来我们看一下封装目录（参考鸿洋大神的github项目）
文件目录
一、封装ViewHolder
public class BaseViewHolder extends RecyclerView.ViewHolder {
//类似HashMap Android用SparseArray性能更高
//管理view
private SparseArray<View> mViews;
//学习过ListView性能优化的肯定知道 这是缓存视图的
private View mConvertView;
private Context mContext;
public BaseViewHolder(Context context, View itemView) {
super(itemView);
mContext = context;
mConvertView = itemView;
mViews = new SparseArray<>();
}
public static BaseViewHolder createViewHolder(Context context, View itemView) {
return new BaseViewHolder(context, itemView);
}
public static BaseViewHolder createViewHolder(Context context,
ViewGroup parent, int layoutId) {
View itemView = LayoutInflater.from(context).inflate(layoutId, parent,
false);
return new BaseViewHolder(context, itemView);
}
/**
* 通过ViewId获取控件
* @author dyb
* @createTime 2017/3/17 22:54
*/
public <T extends View> T getView(int viewId)
{
//先去SparseArray取view
View view = mViews.get(viewId);//viewId 指的是 R.id.XXX这种 对应一个viewId
if (view == null)
{
view = mConvertView.findViewById(viewId);//SparseArray中没有 则到convertView中直接findViewById
mViews.put(viewId, view);//把view放进SparseArray中
}
return (T) view;
}
public View getConvertView() {
return mConvertView;
}
//以下为辅助方法（可略看）
//设置TextView内容
public BaseViewHolder setText(int viewId, String text) {
TextView tv = getView(viewId);
tv.setText(text);
return this;
}
//设置ImageView资源
public BaseViewHolder setImageResource(int viewId, int resId) {
ImageView view = getView(viewId);
view.setImageResource(resId);
return this;
}
//设置ImageView图片Url
public BaseViewHolder setImageUrl(int viewId, String imgUrl) {
ImageView view = getView(viewId);
Glide.with(view.getContext())
.load(imgUrl)
.diskCacheStrategy(DiskCacheStrategy.ALL)
.placeholder(R.drawable.v)//设置加载中图片
.error(R.drawable.v)//设置加载失败图片
.crossFade()//淡入淡出
.fitCenter()//等比例拉伸填满ImageView
.into(view);
return this;
}
//设置ImageView图片Bitmap
public BaseViewHolder setImageBitmap(int viewId, Bitmap bitmap) {
ImageView view = getView(viewId);
view.setImageBitmap(bitmap);
return this;
}
//设置ImageView图片Drawable
public BaseViewHolder setImageDrawable(int viewId, Drawable drawable) {
ImageView view = getView(viewId);
view.setImageDrawable(drawable);
return this;
}
//事件监听
public BaseViewHolder setOnClickListener(int viewId,
View.OnClickListener listener) {
View view = getView(viewId);
view.setOnClickListener(listener);
return this;
}
看一下BaseViewHolder完成的工作：
持有itemView 向外提供getViewByViewId方法
持有itemView：
由构造器传入itemView
或者传入Context context，ViewGroup parent, int layoutId 调用LayoutInflater.from(context).inflate(layoutId, parent,false);生成itemView
向外提供getViewByViewId方法：
传入viewId去获取itemView具体的childrenView（findViewById）
为了提高效率 采用 SparesArray映射存储
二、封装MultiItemTypeAdapter（多类型item适配器）
你可能会问为什么不先封装SingleItemTypeAdapter（单类型item适配器）
实际上SingleItemTypeAdapter是MultiItemTypeAdapter的特例，只要对MultiItemTypeAdapter进行限定就能实现。
public class MultiItemTypeAdapter<T> extends RecyclerView.Adapter<BaseViewHolder> {
protected Context mContext;
protected List<T> mDatas;
protected ItemViewDelegateManager mItemViewDelegateManager;
protected OnItemClickListener<T> mOnItemClickListener;
public int offset = 0;
public MultiItemTypeAdapter(Context context, List<T> datas) {
mContext = context;
mDatas = datas;
mItemViewDelegateManager = new ItemViewDelegateManager();
}
public MultiItemTypeAdapter(Context context) {
this(context, new ArrayList<T>());
}
@Override
public int getItemViewType(int position) {
if (!useItemViewDelegateManager())
return super.getItemViewType(position);
return mItemViewDelegateManager.getItemViewType(mDatas.get(position), position);
}
@Override
public BaseViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
int layoutId = mItemViewDelegateManager.getItemViewLayoutId(viewType);
BaseViewHolder holder = BaseViewHolder.createViewHolder(mContext, parent, layoutId);
setListener(parent, holder, viewType);
return holder;
}
public void convert(BaseViewHolder holder, T t) {
mItemViewDelegateManager.convert(holder, t, holder.getAdapterPosition());
}
protected boolean isEnabled(int viewType) {
return true;
}
protected void setListener(final ViewGroup parent, final BaseViewHolder viewHolder, int
viewType) {
if (!isEnabled(viewType))
return;
viewHolder.getConvertView().setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
if (mOnItemClickListener != null) {
int position = viewHolder.getAdapterPosition();
mOnItemClickListener.onItemClick(v, viewHolder, mDatas.get(position - offset)
, position);
}
}
});
viewHolder.getConvertView().setOnLongClickListener(new View.OnLongClickListener() {
@Override
public boolean onLongClick(View v) {
if (mOnItemClickListener != null) {
int position = viewHolder.getAdapterPosition();
return mOnItemClickListener.onItemLongClick(v, viewHolder, mDatas.get
(position - offset), position);
}
return false;
}
});
}
//将数据与界面进行绑定的操作
@Override
public void onBindViewHolder(BaseViewHolder holder, int position) {
convert(holder, mDatas.get(position));
}
//获取数据的数量
@Override
public int getItemCount() {
int itemCount = mDatas.size();
return itemCount;
}
public List<T> getDatas() {
return mDatas;
}
public MultiItemTypeAdapter addItemViewDelegate(ItemViewDelegate<T> itemViewDelegate) {
mItemViewDelegateManager.addDelegate(itemViewDelegate);
return this;
}
public MultiItemTypeAdapter addItemViewDelegate(int viewType, ItemViewDelegate<T>
itemViewDelegate) {
mItemViewDelegateManager.addDelegate(viewType, itemViewDelegate);
return this;
}
protected boolean useItemViewDelegateManager() {
return mItemViewDelegateManager.getItemViewDelegateCount() > 0;
}
public interface OnItemClickListener<T> {
void onItemClick(View view, RecyclerView.ViewHolder holder, T o, int position);
boolean onItemLongClick(View view, RecyclerView.ViewHolder holder, T o, int position);
}
public void setOnItemClickListener(OnItemClickListener onItemClickListener) {
this.mOnItemClickListener = onItemClickListener;
}
public void addDataAll(List data) {
mDatas.addAll(data);
}
public void clearData() {
mDatas.clear();
}
}
public class ItemViewDelegateManager<T> {
SparseArrayCompat<ItemViewDelegate<T>> delegates = new SparseArrayCompat();
public int getItemViewDelegateCount() {
return delegates.size();
}
public ItemViewDelegateManager<T> addDelegate(ItemViewDelegate<T> delegate) {
int viewType = delegates.size();
if (delegate != null) {
delegates.put(viewType, delegate);
viewType++;
}
return this;
}
public ItemViewDelegateManager<T> addDelegate(int viewType, ItemViewDelegate<T> delegate) {
if (delegates.get(viewType) != null) {
throw new IllegalArgumentException("An ItemViewDelegate is already registered for the" +
" viewType = " + viewType + ". Already registered ItemViewDelegate is " +
delegates
.get(viewType));
}
delegates.put(viewType, delegate);
return this;
}
public ItemViewDelegateManager<T> removeDelegate(ItemViewDelegate<T> delegate) {
if (delegate == null) {
throw new NullPointerException("ItemViewDelegate is null");
}
int indexToRemove = delegates.indexOfValue(delegate);
if (indexToRemove >= 0) {
delegates.removeAt(indexToRemove);
}
return this;
}
public ItemViewDelegateManager<T> removeDelegate(int itemType) {
int indexToRemove = delegates.indexOfKey(itemType);
if (indexToRemove >= 0) {
delegates.removeAt(indexToRemove);
}
return this;
}
public int getItemViewType(T item, int position) {
int delegatesCount = delegates.size();
for (int i = delegatesCount - 1; i >= 0; i--) {
ItemViewDelegate<T> delegate = delegates.valueAt(i);
if (delegate.isForViewType(item, position)) {
return delegates.keyAt(i);
}
}
throw new IllegalArgumentException("No ItemViewDelegate added that matches position=" +
position + " in data source");
}
public void convert(BaseViewHolder holder, T item, int position) {
int delegatesCount = delegates.size();
for (int i = 0; i < delegatesCount; i++) {
ItemViewDelegate<T> delegate = delegates.valueAt(i);
if (delegate.isForViewType(item, position)) {
delegate.convert(holder, item, position);
return;
}
}
throw new IllegalArgumentException("No ItemViewDelegateManager added that matches " +
"position=" + position + " in data source");
}
public int getItemViewLayoutId(int viewType) {
return delegates.get(viewType).getItemViewLayoutId();
}
public int getItemViewType(ItemViewDelegate itemViewDelegate) {
return delegates.indexOfValue(itemViewDelegate);
}
}
public interface ItemViewDelegate<T> {
//向 Adapter 提供布局文件的 id
int getItemViewLayoutId();
//判断传入的 item 是不是自己应该处理的类型
boolean isForViewType(T item, int position);
//绑定 holder 和数据
void convert(BaseViewHolder holder, T t, int position);
}
重点：
一个item对应一个ItemViewDelegate接口 实现
//向 Adapter 提供布局文件的 id
//判断传入的 item 是不是自己应该处理的类型
//绑定 holder 和数据
ItemViewDelegateManager 管理ItemViewDelegate
用到了SparseArrayCompat来管理ItemViewDelegate
SparseArrayCompat其实是一个map容器,它使用了一套算法优化了hashMap,可以节省至少50%的缓存.
缺点但是有局限性只针对下面类型.
key: Integer; value: object
因此当HshMap()的key是Integer类型时推荐使用SparseArrayCompat(),用法与Map相似.
重点看这个数据绑定的逻辑
在数据绑定时遍历SparseArrayCompat中的ItemViewDelegate
根据ItemViewDelegate实现的isForViewType(item, position)方法
来判断是否由当前ItemViewDelegate来处理数据绑定
Paste_Image.png
三、封装SingleItemTypeAdapter
上面也说过了SingleItemTypeAdapter的实现只要对MultiItemTypeAdapter进行一些限定：
getItemViewLayoutId 限定为一种layoutId
isForViewType 永远返回true
convert 数据绑定还是交由具体子类去实现
public abstract class SingleItemTypeAdapter<T> extends MultiItemTypeAdapter<T> {
protected Context mContext;
protected int mLayoutId;
protected List<T> mDatas;
protected LayoutInflater mInflater;
public SingleItemTypeAdapter(final Context context, final int layoutId) {
this(context, layoutId, new ArrayList<T>());
}
public SingleItemTypeAdapter(final Context context, final int layoutId, List<T> datas) {
super(context, datas);
mContext = context;
mInflater = LayoutInflater.from(context);
mLayoutId = layoutId;
mDatas = datas;
addItemViewDelegate(new ItemViewDelegate<T>() {
@Override
public int getItemViewLayoutId() {
return layoutId;
}
@Override
public boolean isForViewType(T item, int position) {
return true;
}
@Override
public void convert(BaseViewHolder holder, T t, int position) {
SingleItemTypeAdapter.this.convert(holder, t, position);
}
});
}
protected abstract void convert(BaseViewHolder holder, T t, int position);
}
