这次封装了recycleview的adapter。众所周知，recycleview可塑性很强，可是谷歌爸爸把许多listview常用的功能给去掉了，让我们自己封装。之前就遇到过很尴尬的事，有个情景是需要给你自己的adapter添加个头部布局，但是发现竟然没有！！由于项目紧急，只好先用listview来代替recycleview。今天，终于回过神来搞定了recycleview的头部添加方法，为了以后使用方便，变成依赖形式方便大家使用。
使用方法：
主路径的build文件里下添加maven{url'https://jitpack.io'}，项目的build文件里添加
compile'com.github.Rainorsad:RecycleItemOrition:v3.0'
好，我们转身看一下使用方法：
是不是和原生的Recycleview.Adapter很像，其实就是很想，封装后要的就是简洁明了，大部分封装代码在下面说，接下来在adapter中调用的话就是
前两行是设置adapter，后两行是设置头部view。注意，在设置头部view这里，如果你的头部view就是一个静态界面不需要交互的话，那么直解用
adapter.addHeaderView(LayoutInflater.from(this).inflate(R.layout.xxx,null))
的方式就好，如果涉及到交互的话，那么你需要重新自定义写HeadView，简单的写法如下所示：
用法讲解完了，我们一起来看看内部到底怎么封装的代码。
```
public abstract classHFViewAdapterextendsRecyclerView.Adapter{
privateContextc;
privateListdata;
privateRecyclerViewmRecyclerView;
private intTYPE_HEADVIEW=1001;
private intTYPE_FOOTVIEW=2002;
private intTYPE_NORMAL=3003;
privateViewheadView;
privateViewfootView;
protectedHFViewAdapter(Context c,List s) {
this.c= c;
this.data= s;
}
@Override
publicRecyclerView.ViewHolderonCreateViewHolder(ViewGroup parent, intviewType) {
if(viewType ==TYPE_HEADVIEW){
return newMyViewHolder(headView);
}else if(viewType ==TYPE_FOOTVIEW){
return newMyViewHolder(footView);
}else{
returnonCreateViewHolde(parent,viewType);
}
}
@Override
public voidonBindViewHolder(RecyclerView.ViewHolder holder, intposition) {
if(!isHeaderView(position) && !isFooterView(position)){
if(haveHeaderView()) position--;
onBindViewHolde(holder,position);
}
}
@Override
public intgetItemCount() {
intcount = getItemCounts();
if(footView!=null) {
count++;
}
if(headView!=null) {
count++;
}
returncount;
}
@Override
public intgetItemViewType(intposition) {
if(isHeaderView(position)){
returnTYPE_HEADVIEW;
}else if(isFooterView(position)){
returnTYPE_FOOTVIEW;
}else{
returnTYPE_NORMAL;
}
}
@Override
public voidonAttachedToRecyclerView(RecyclerView recyclerView) {
try{
if(mRecyclerView==null&&mRecyclerView!= recyclerView) {
mRecyclerView= recyclerView;
}
ifGridLayoutManager();
}catch(Exception e) {
e.printStackTrace();
}
}
public voidaddHeaderView(View headerView) {
if(haveHeaderView()) {
throw newIllegalStateException("hearview has already exists!");
}else{
//避免出现宽度自适应
ViewGroup.LayoutParams params =newViewGroup.LayoutParams
(ViewGroup.LayoutParams.MATCH_PARENT,ViewGroup.LayoutParams.WRAP_CONTENT);
headerView.setLayoutParams(params);
headView= headerView;
ifGridLayoutManager();
notifyItemInserted(0);
}
}
public voidaddFooterView(View footerView) {
if(haveFooterView()) {
throw newIllegalStateException("footerView has already exists!");
}else{
ViewGroup.LayoutParams params =newViewGroup.LayoutParams
(ViewGroup.LayoutParams.MATCH_PARENT,ViewGroup.LayoutParams.WRAP_CONTENT);
footerView.setLayoutParams(params);
footView= footerView;
ifGridLayoutManager();
notifyItemInserted(getItemCount() -1);
}
}
private voidifGridLayoutManager() {
if(mRecyclerView==null)return;
finalRecyclerView.LayoutManager layoutManager =mRecyclerView.getLayoutManager();
if(layoutManagerinstanceofGridLayoutManager) {
finalGridLayoutManager.SpanSizeLookup originalSpanSizeLookup = ((GridLayoutManager) layoutManager).getSpanSizeLookup();
((GridLayoutManager) layoutManager).setSpanSizeLookup(newGridLayoutManager.SpanSizeLookup() {
@Override
public intgetSpanSize(intposition) {
return(isHeaderView(position) || isFooterView(position)) ? ((GridLayoutManager)layoutManager).getSpanCount() :1;
}
});
}
}
protected abstractRecyclerView.ViewHolderonCreateViewHolde(ViewGroup parent, intviewType);
protected abstract voidonBindViewHolde(RecyclerView.ViewHolder holder, intposition);
protected abstract intgetItemCounts();
private booleanhaveHeaderView() {
returnheadView!=null;
}
public booleanhaveFooterView() {
returnfootView!=null;
}
private booleanisHeaderView(intposition) {
returnhaveHeaderView() && position ==0;
}
private booleanisFooterView(intposition) {
returnhaveFooterView() && position == getItemCount() -1;
}
classMyViewHolderextendsRecyclerView.ViewHolder{
publicMyViewHolder(View itemView) {
super(itemView);
}
}
}
```
