android之实现万能适配RecyclerView的adapter
现在基本大家都推荐RecyclerView，很少有人使用ListView了，包括我自己也是，已经很久没用ListView了，所以关于ListView的万能adapter就不写了。
每次写项目的时候，每次遇到RecyclerView都要重新写一个Adapter，一大堆东西重复写，麻烦死了，实在是忍不住了，以前懒，总是懒得去搞快捷的adapter，现在项目里面好多个RecyclerView，马丹，写adapter写吐，所以麻溜麻溜的来写个万能adapter了，这种东西网上很多，原理差不多都是重写ViewHolder和Adapter，主要是使用泛型实现。废话不多说，撸代码吧。
注意：我的万能adapter中集成了下拉刷新、上拉加载更多、另增header的功能，需要与我后面将写到的万能下拉刷新、上拉加载更多的RecyclerView搭配使用，如果你不需要下拉刷新和上拉加载更多可以无视其中相关的代码。
首先，我们知道我们对adapter中控件获取都是通过ViewHolder来的，所以我们首先要自定义ViewHolder，来完成各个控件的获取和初始化。正常情况下，我们是这样用的：
class HistoryGoodsHolder extends RecyclerView.ViewHolder {
ImageView img;
TextView name, summary, amount, price;
public HistoryGoodsHolder(View itemView) {
super(itemView);
img = (ImageView) itemView.findViewById(R.id.item_history_rcv_goodsImg);
name = (TextView) itemView.findViewById(R.id.item_history_rcv_goodsName);
summary = (TextView) itemView.findViewById(R.id.item_history_rcv_goodsSummary);
amount = (TextView) itemView.findViewById(R.id.item_history_rcv_goodsAmount);
price = (TextView) itemView.findViewById(R.id.item_history_rcv_goodsPrice);
}
}现在我们需要实现的是万能的adapter，所以holder必须实现可定制化，而不是这种固定死的，每个RecyclerView的item布局不一样就重新写个holder，这样就没有意义了，所以我们写的万能Holder中不能存在真实的控件id，因为一旦id固定，那么肯定得重复写holder，毕竟id不一样，holder就不一样了，所以我们可以通过一种方式，那就是findById方法里面的id不写死，而是用参数的方式传进去，这样可以写一个通用的Holer，不同的recyclerview可以传不同的id进去就行了。ViewHolder最终形态：
public class XJJBaseRvHolder extends RecyclerView.ViewHolder {
private SparseArray mViews; //view的集合
private View mConvertView; //item的布局
private Context mContext; //上下文
public XJJBaseRvHolder(Context context, View itemView) {
super(itemView);
mContext = context;
mConvertView = itemView;
mViews = new SparseArray();
}
//获取item的布局
public View getItemView(){
return mConvertView;
}
//初始化控件，通过传进去id来初始化，使用泛型实现传递任何类型
public T getView(int viewId)
{
View view = mViews.get(viewId);
if (view == null)
{
view = mConvertView.findViewById(viewId);
mViews.put(viewId, view);
}
return (T) view;
}
//快捷设置TextView的文本
public XJJBaseRvHolder setText(int viewId, String text)
{
TextView tv = getView(viewId);
tv.setText(text);
return this;
}
//快捷设置ImageView的图片
public XJJBaseRvHolder setSrc(int viewId, int resId)
{
ImageView view = getView(viewId);
view.setImageResource(resId);
return this;
}
//设置控件的点击事件
public XJJBaseRvHolder setOnClickListener(int viewId, View.OnClickListener listener)
{
View view = getView(viewId);
view.setOnClickListener(listener);
return this;
}
//设置item的点击事件
public XJJBaseRvHolder setItemOnClickListener(View.OnClickListener listener){
mConvertView.setOnClickListener(listener);
return this;
} ViewHolder搞定，接下来是adapter，ViewHolder是在adapter里面被引用的，如果我们在adapter里面实例化holder后传入id来初始化控件，肯定不行，因为如果在adapter里面传入id，那么adapter使用了真实的id，那么id不一样adapter又得不一样，还得重复写了，所以我们不能在adapter里面传入id来初始化item的控件，那么怎么实现呢？用接口来实现，具体如下：
先写接口把Holder传递出去，然后初始化adapter的时候实现改接口。
public interface ItemDataListener {//接口
void setItemData(XJJBaseRvHolder holder, T t);
}
public void setItemDataListener(ItemDataListener listener) {
itemDataListener = listener;
} 然后我们数据填充的时候需要先初始化控件的，所以我在onBindViewHolder里面调用接口，让初始化和数据填充在外面执行。
@Override
public void onBindViewHolder(final XJJBaseRvHolder holder, int position) {
if (getItemViewType(position) == TYPE_HEADER || getItemViewType(position) == TYPE_PULL_TO_REFRESH_HEADER) {//如果是头部，不做数据填充
return;
} else if (getItemViewType(position) == TYPE_FOOTER) {
return;
} else {
if (itemDataListener == null) {
return;
}
itemDataListener.setItemData(holder, datas.get(getRealPosition(holder)));
}
}实现接口并初始化控件填充数据：
adapter.setItemDataListener(new XJJBaseRvAdapter.ItemDataListener<Integer>() {
@Override
public void setItemData(final XJJBaseRvHolder holder, Integer integer) {
TextView textView = holder.getView(R.id.item_index_tv);
textView.setText(String.valueOf(integer));
}
});以上就是控件初始化和数据填充的思路流程，可能讲的不是很清楚？水平有限啊，从小语文就不好啊，看不懂的你们可以看鸿洋大神的，这部分思路是借鉴鸿洋大神的。
接下来，就是设正常的header、下拉刷新头、上拉加载更多footer了。
首先需要3个变量代表四种类型（上面三种+正常数据）。
public static final int TYPE_HEADER = 0; //正常头部
public static final int TYPE_PULL_TO_REFRESH_HEADER = 1; //下拉刷新头部
public static final int TYPE_NORMAL = 2; //正常数据
public static final int TYPE_FOOTER = 3; //上拉footer然后添加的实现方法：
//添加下拉刷新头
public void addPullToRefreshHeaderView(View
addPullToRefreshHeaderView) {
if (headerView != null) return; //如果已经先添加了headerView，就不能增加下拉头了
if (pullToRefreshHeaderView != null || addPullToRefreshHeaderView == null) {
return;
}
this.pullToRefreshHeaderView = addPullToRefreshHeaderView;
notifyItemInserted(0);
}
//添加头部布局（非下拉头），仅限一个
public void addHeaderView(View addHeaderView) {
if (addHeaderView == null || headerView != null) {
return;
}
this.headerView = addHeaderView;
notifyItemInserted(pullToRefreshHeaderView == null ? 0 : 1);
}
//添加footeer
public void addLoadMoreFooterView(View addLoadMoreFooterView) {
if (loadMoreFooterView != null || addLoadMoreFooterView == null) {
return;
}
this.loadMoreFooterView = addLoadMoreFooterView;
notifyItemInserted(getItemCount() - 1);
}然后设置ViewType:
@Override
public int getItemViewType(int position) {
if (loadMoreFooterView != null && position == getItemCount() - 1) {
return TYPE_FOOTER;
}
if (pullToRefreshHeaderView == null && headerView == null) {
return TYPE_NORMAL;
}
if (pullToRefreshHeaderView == null && headerView != null) {
if (position == 0) {
return TYPE_HEADER;
}
}
if (pullToRefreshHeaderView != null && headerView == null) {
if (position == 0) {
return TYPE_PULL_TO_REFRESH_HEADER;
}
}
if (pullToRefreshHeaderView != null && headerView != null) {
if (position == 0) return TYPE_PULL_TO_REFRESH_HEADER;
if (position == 1) return TYPE_HEADER;
}
return TYPE_NORMAL;
}接下来需要获取真实的position，因为正常情况下RecyclerView中position为0的item跟我们数据data（一般是List类型）的data.get(0)对应，但是由于添加了header所以header的position才是0，数据对应不上，所以我们得修改下position获取方式：
//获取真实的position（与datalist对应，因为添加了头部，会使得position和data对应不上）
public int getRealPosition(RecyclerView.ViewHolder holder) {
int position = holder.getLayoutPosition();
if (pullToRefreshHeaderView == null) {
return headerView == null ? position : position - 1;
} else {
return headerView == null ? position - 1 : position - 2;
}
}然后呢，我们还要修改getItemCount，因为添加了header和footer，所以Item数量变了：
@Override
public int getItemCount() {
if (pullToRefreshHeaderView == null) {
if (headerView == null) {
return loadMoreFooterView == null ? datas.size() : datas.size() + 1;
} else {
return loadMoreFooterView == null ? datas.size() + 1 : datas.size() + 2;
}
} else {
if (headerView == null) {
return loadMoreFooterView == null ? datas.size() + 1 : datas.size() + 2;
} else {
return loadMoreFooterView == null ? datas.size() + 2 : datas.size() + 3;
}
}
}其次是onCreateViewHolder，也要根据不同类型生成不同的holder：
@Override
public XJJBaseRvHolder onCreateViewHolder(ViewGroup parent, int viewType) {
if (pullToRefreshHeaderView != null && viewType == TYPE_PULL_TO_REFRESH_HEADER) {//如果是下拉头
DisplayMetrics dm = new DisplayMetrics();
WindowManager wm = (WindowManager) context.getSystemService(Context.WINDOW_SERVICE);
wm.getDefaultDisplay().getMetrics(dm);
LinearLayout.LayoutParams layoutParams = new LinearLayout.LayoutParams(dm.widthPixels, ViewGroup.LayoutParams.WRAP_CONTENT);
pullToRefreshHeaderView.setLayoutParams(layoutParams);
return new XJJBaseRvHolder(context, pullToRefreshHeaderView);
}
if (headerView != null && viewType == TYPE_HEADER) {//如果是正常头
DisplayMetrics dm = new DisplayMetrics();
WindowManager wm = (WindowManager) context.getSystemService(Context.WINDOW_SERVICE);
wm.getDefaultDisplay().getMetrics(dm);
LinearLayout.LayoutParams layoutParams = new LinearLayout.LayoutParams(dm.widthPixels, ViewGroup.LayoutParams.WRAP_CONTENT);
headerView.setLayoutParams(layoutParams);
return new XJJBaseRvHolder(context, headerView);
}
if (loadMoreFooterView != null && viewType == TYPE_FOOTER) {
DisplayMetrics dm = new DisplayMetrics();
WindowManager wm = (WindowManager) context.getSystemService(Context.WINDOW_SERVICE);
wm.getDefaultDisplay().getMetrics(dm);
LinearLayout.LayoutParams layoutParams = new LinearLayout.LayoutParams(dm.widthPixels, ViewGroup.LayoutParams.WRAP_CONTENT);
loadMoreFooterView.setLayoutParams(layoutParams);
return new XJJBaseRvHolder(context, loadMoreFooterView);
}
View view = LayoutInflater.from(context).inflate(layoutId, parent, false);
XJJBaseRvHolder holder = new XJJBaseRvHolder(context, view);
return holder;
}可能有的朋友看不明白，其实还是很简单的，多看两遍就明白了，我把总的贴出来吧。adapter最终形态：
public class XJJBaseRvAdapter extends RecyclerView.Adapter {
protected Context context;
protected ItemDataListener itemDataListener;
private View pullToRefreshHeaderView, headerView, loadMoreFooterView;
protected int layoutId;
protected List datas;
public static final int TYPE_HEADER = 0; //正常头部
public static final int TYPE_PULL_TO_REFRESH_HEADER = 1; //下拉刷新头部
public static final int TYPE_NORMAL = 2; //正常数据
public static final int TYPE_FOOTER = 3; //上拉footer
public XJJBaseRvAdapter(Context context, int layoutId, List datas) {
this.context = context;
this.layoutId = layoutId;
this.datas = datas;
}
public void setDatas(List datas) {
this.datas = datas;
notifyDataSetChanged();
}
//添加下拉刷新头
public void addPullToRefreshHeaderView(View addPullToRefreshHeaderView) {
if (headerView != null) return; //如果已经先添加了headerView，就不能增加下拉头了
if (pullToRefreshHeaderView != null || addPullToRefreshHeaderView == null) {
return;
}
this.pullToRefreshHeaderView = addPullToRefreshHeaderView;
notifyItemInserted(0);
}
//添加头部布局（非下拉头），仅限一个
public void addHeaderView(View addHeaderView) {
if (addHeaderView == null || headerView != null) {
return;
}
this.headerView = addHeaderView;
notifyItemInserted(pullToRefreshHeaderView == null ? 0 : 1);
}
//添加footeer
public void addLoadMoreFooterView(View addLoadMoreFooterView) {
if (loadMoreFooterView != null || addLoadMoreFooterView == null) {
return;
}
this.loadMoreFooterView = addLoadMoreFooterView;
notifyItemInserted(getItemCount() - 1);
}
public View getPullToRefreshHeaderView(){
return pullToRefreshHeaderView;
}
public View getLoadMoreFooterView(){
return loadMoreFooterView;
}
@Override
public int getItemViewType(int position) {
if (loadMoreFooterView != null && position == getItemCount() - 1) {
return TYPE_FOOTER;
}
if (pullToRefreshHeaderView == null && headerView == null) {
return TYPE_NORMAL;
}
if (pullToRefreshHeaderView == null && headerView != null) {
if (position == 0) {
return TYPE_HEADER;
}
}
if (pullToRefreshHeaderView != null && headerView == null) {
if (position == 0) {
return TYPE_PULL_TO_REFRESH_HEADER;
}
}
if (pullToRefreshHeaderView != null && headerView != null) {
if (position == 0) return TYPE_PULL_TO_REFRESH_HEADER;
if (position == 1) return TYPE_HEADER;
}
return TYPE_NORMAL;
}
//获取真实的position（与datalist对应，因为添加了头部，会使得position和data对应不上）
public int getRealPosition(RecyclerView.ViewHolder holder) {
int position = holder.getLayoutPosition();
if (pullToRefreshHeaderView == null) {
return headerView == null ? position : position - 1;
} else {
return headerView == null ? position - 1 : position - 2;
}
}
public void setItemDataListener(ItemDataListener listener) {
itemDataListener = listener;
}
@Override
public XJJBaseRvHolder onCreateViewHolder(ViewGroup parent, int viewType) {
if (pullToRefreshHeaderView != null && viewType == TYPE_PULL_TO_REFRESH_HEADER) {//如果是下拉头
DisplayMetrics dm = new DisplayMetrics();
WindowManager wm = (WindowManager) context.getSystemService(Context.WINDOW_SERVICE);
wm.getDefaultDisplay().getMetrics(dm);
LinearLayout.LayoutParams layoutParams = new LinearLayout.LayoutParams(dm.widthPixels, ViewGroup.LayoutParams.WRAP_CONTENT);
pullToRefreshHeaderView.setLayoutParams(layoutParams);
return new XJJBaseRvHolder(context, pullToRefreshHeaderView);
}
if (headerView != null && viewType == TYPE_HEADER) {//如果是正常头
DisplayMetrics dm = new DisplayMetrics();
WindowManager wm = (WindowManager) context.getSystemService(Context.WINDOW_SERVICE);
wm.getDefaultDisplay().getMetrics(dm);
LinearLayout.LayoutParams layoutParams = new LinearLayout.LayoutParams(dm.widthPixels, ViewGroup.LayoutParams.WRAP_CONTENT);
headerView.setLayoutParams(layoutParams);
return new XJJBaseRvHolder(context, headerView);
}
if (loadMoreFooterView != null && viewType == TYPE_FOOTER) {
DisplayMetrics dm = new DisplayMetrics();
WindowManager wm = (WindowManager) context.getSystemService(Context.WINDOW_SERVICE);
wm.getDefaultDisplay().getMetrics(dm);
LinearLayout.LayoutParams layoutParams = new LinearLayout.LayoutParams(dm.widthPixels, ViewGroup.LayoutParams.WRAP_CONTENT);
loadMoreFooterView.setLayoutParams(layoutParams);
return new XJJBaseRvHolder(context, loadMoreFooterView);
}
View view = LayoutInflater.from(context).inflate(layoutId, parent, false);
XJJBaseRvHolder holder = new XJJBaseRvHolder(context, view);
return holder;
}
@Override
public void onBindViewHolder(final XJJBaseRvHolder holder, int position) {
if (getItemViewType(position) == TYPE_HEADER || getItemViewType(position) == TYPE_PULL_TO_REFRESH_HEADER) {//如果是头部，不做数据填充
return;
} else if (getItemViewType(position) == TYPE_FOOTER) {
return;
} else {
if (itemDataListener == null) {
return;
}
itemDataListener.setItemData(holder, datas.get(getRealPosition(holder)));
}
}
@Override
public int getItemCount() {
if (pullToRefreshHeaderView == null) {
if (headerView == null) {
return loadMoreFooterView == null ? datas.size() : datas.size() + 1;
} else {
return loadMoreFooterView == null ? datas.size() + 1 : datas.size() + 2;
}
} else {
if (headerView == null) {
return loadMoreFooterView == null ? datas.size() + 1 : datas.size() + 2;
} else {
return loadMoreFooterView == null ? datas.size() + 2 : datas.size() + 3;
}
}
}
public interface ItemDataListener {
void setItemData(XJJBaseRvHolder holder, T t);
}
} 用法：
XJJBaseRvAdapter adapter = new XJJBaseRvAdapter(this, R.layout.item_rcv, mdatas);//传入item布局
adapter.setItemDataListener(new XJJBaseRvAdapter.ItemDataListener() {
@Override
public void setItemData(final XJJBaseRvHolder holder, Integer integer) {
TextView textView = holder.getView(R.id.item_index_tv);//初始化控件
textView.setText(String.valueOf(integer));
}
}); 很简单的，初始化adapter时传入item的布局即可，然后实现接口在里面做数据处理即可。
如果大家有不懂的可以留言或者看鸿洋大神的相关博客，他那里比较详细，我这里需要是为了给后面的文章（万能的下拉刷新、上拉加载更多）做个铺垫，因为后面的跟这个万能adapter配合用的，以后用起来都方便。有不当之处还望见谅。