RecyclerView.Adapter通用性

对于一个写代码有洁癖、始终重复的写同样而不简洁的代码，是无法忍受的。

一个APP中，RecyclerView和ListView的使用会比较频繁。需要的时候，都会重复的写Adapter。这样使得不够通用，不够简洁。下面就针对RecyclerView.Adapter展开来写。

RecyclerView是由多个item组成的，这里我们可以把每一项item看成一个DataHolder, DataHolder的代码如下：

public abstract class DataHolder {    private Object   mData          = null;    private int mType;    public DataHolder(Object data, int type){        mData = data;        mType = type;    }    public abstract GenericViewHolder onCreateView(Context context);    public abstract void onBindView(Context context, GenericViewHolder holder, int position, Object data);    public Object getData()    {        return mData;    }    public int getType() {        return mType;    }}

1.构造函数中两个参数，第一个参数data是一个实体类(界面上需要展示的数据)，第二个参数type是item的布局类型(Adapter中可以有多种不同类型的布局)

2.两个抽象方法onCreateView()和onBindView()是不是很眼熟。没错，就是仿照Adapter的onCreateViewHolder()和onBindViewHolder()写的，用法大致相同，前者初始化布局，后者设置数据。

RecyclerView中使用ViewHolder来缓存布局，避免多次实例化，也仿照写了GenericViewHolder，如下：

public class GenericViewHolder extends RecyclerView.ViewHolder {    protected View[] mParams = null;    protected Object mTag    = null;    public GenericViewHolder(View itemView,View... params) {        super(itemView);        mParams = params;    }    public void setParams(View... params)    {        mParams = params;    }    public View[] getParams()    {        return mParams;    }    public void setTag(Object tag)    {        mTag = tag;    }    public Object getTag()    {        return mTag;    }}

1.构造函数中itemView就是onCreateView()中初始化的布局，params就是初始化的控件

2.getParams();获取初始化的控件

最重要的Adapter来了，GenericAdapter继承RecyclerView.Adapter，如下：

public class GenericAdapter extends RecyclerView.Adapter<GenericViewHolder> {    private Context mContext = null;    private List<DataHolder> mHolders = null;    public GenericAdapter(Context context){        mContext = context;        mHolders = new ArrayList<>();    }    public Context getContext(){        return mContext;    }    public void addDataHolder(DataHolder holder)    {        mHolders.add(holder);//        notifyDataSetChanged();    }    public void addDataHolder(int location, DataHolder holder)    {        mHolders.add(location, holder);        notifyDataSetChanged();    }    public void addDataHolders(List<DataHolder> holders)    {        mHolders.addAll(holders);        notifyDataSetChanged();    }    public void addDataHolders(int location, List<DataHolder> holders)    {        mHolders.addAll(location, holders);        notifyDataSetChanged();    }    public void removeDataHolder(int location)    {        mHolders.remove(location);        notifyDataSetChanged();    }    public void removeDataHolder(DataHolder holder)    {        mHolders.remove(holder);        notifyDataSetChanged();    }    public void removeDataHolders(int start){        int size = mHolders.size();        if(start >=0 && start < size){            while(start < size){                mHolders.remove(size - 1);                size = mHolders.size();            }        }        notifyDataSetChanged();    }    public void clearDataHolders(boolean isNotify){        mHolders.clear();        if(isNotify)notifyDataSetChanged();    }    public List<DataHolder> getData(){        return mHolders;    }    /**     * 根据布局类型查DataHolder     * @param viewType     * @return     */    public DataHolder queryDataHolder(int viewType)    {        int size = mHolders.size();        for(int i = 0 ; i < size;i++){            DataHolder holder = mHolders.get(i);            if(viewType == holder.getType()){                return holder;            }        }        return null;    }    @Override    public GenericViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {        DataHolder holder = queryDataHolder(viewType);        return holder.onCreateView(mContext);    }    @Override    public final void onBindViewHolder(GenericViewHolder viewHolder, int position) {        DataHolder holder = mHolders.get(position);        holder.onBindView(mContext,viewHolder,position,holder.getData());    }    @Override    public final int getItemCount() {        return mHolders.size();    }    @Override    public int getItemViewType(int position) {        return mHolders.get(position).getType();    }    @Override    public final long getItemId(int position) {        return super.getItemId(position);    }}

1.重写onCreateViewHolder，该方法中调用了queryDataHolder()方法，此方法是根据布局类型，找出对应该类型的DataHolder；找到对应的DataHolder后，在调用不同类型布局的onCreateView(),分别进行实例化。

2.重写onBindViewHolder，该方法会执行DataHolder中的onBindView()，用来设置数据

3.addDataHolder()方法,向Adapter中添加item

4.addDataHolders()方法,向Adapter中添加数据集的item

demo地址:https://github.com/SimpleWei00/GenericAdapter