使用RecyclerView加载不出数据的原因可能有：

一、先检查适配器#####

查看适配器是否有误，
检查getItemCount()方法中是否 return data.size();

public class RecyclerViewAdapter extends RecyclerView.Adapter<RecyclerViewAdapter.ViewHolder> {
    private List<String> data = new ArrayList<>();
    private Context context;
    private LayoutInflater inflater;

    public RecyclerViewAdapter(Context context, List<String> data) {
        this.data = data;
        this.context = context;
        inflater=LayoutInflater.from(context);
    }


    @Override
    public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View view = inflater.inflate(R.layout.recycler_view_item,null);
        ViewHolder   viewHolder = new ViewHolder(view);
        return viewHolder;
    }

    @Override
    public void onBindViewHolder(ViewHolder holder, int position) {
        holder.tv.setText(data.get(position));
    }

    @Override
    public int getItemCount() {
        return data.size();
    }

    class ViewHolder extends RecyclerView.ViewHolder {

        TextView tv;

        public ViewHolder(View view) {
            super(view);
            tv=(TextView) view.findViewById(R.id.tv_item);
        }

    }
}

二、无数据#####

启动发现有错，指向adapter中的getItemCount()方法，并报了一个空指针异常，说明没有数据

           java.lang.NullPointerException: Attempt to invoke interface method 'int java.util.List.size()' on a null object reference
                                                   at wapchief.top.retrofitrxjavatest.RecyclerViewAdapter.getItemCount(RecyclerViewAdapter.java:47)

三、布局管理器配置#####

在onCreate方法中实现：

        //数据源
        datas();
        adapter=new RecyclerViewAdapter(this,data);
        recyclerView.setLayoutManager(new LinearLayoutManager(this));
        recyclerView.setAdapter(adapter);

四、onCreate方法#####

对比两种方法，
如果在onCreate（Bundle savedInstanceState, PersistableBundle persistentState）中使用
需要在AndroidManifest.xml文件下Activity中注册权限：

<activity android:name=".RecyclerViewActivity"
      android:persistableMode="persistAcrossReboots"/>

在onCreate(Bundle savedInstanceState)中则不需要

@Override
    public void onCreate(Bundle savedInstanceState, PersistableBundle persistentState) {
        super.onCreate(savedInstanceState, persistentState);
    }
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);