对于那些在片段中使用RecyclerView并从其他视图中扩展它的人:当扩展整个片段视图时，确保将RecyclerView绑定到它的根视图。

我为适配器正确地连接和做了所有事情，但我从未进行绑定。 @Prateek Agarwal的回答已经为我提供了一切，但这里有更详细的说明。

科特林

    override fun onCreateView(inflater: LayoutInflater?, container: ViewGroup?, savedInstanceState: Bundle?): View? {

    val rootView =  inflater?.inflate(R.layout.fragment_layout, container, false)
    recyclerView = rootView?.findViewById(R.id.recycler_view_id)
    // rest of my stuff
    recyclerView?.setHasFixedSize(true)
    recyclerView?.layoutManager = viewManager
    recyclerView?.adapter = viewAdapter
    // return the root view
    return rootView
}

Java

  @Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {

    View rootView= inflater.inflate(R.layout.fragment_layout,container,false);
    recyclerview= rootView.findViewById(R.id.recycler_view_id);
    return rootView;
}

 override fun onCreateView(...  ): View? 
   {
        val rootview = inflater.inflate(R.layout.fragment_menu, 
        container,false)

        val recycler_menu_list = 
         rootview.findViewById(R.id.recycler_menu_list) as RecyclerView

        recycler_menu_list.layoutManager = LinearLayoutManager(activity)

        val data =  ...

        foodCardAdapter = FoodCardAdapter()

        recycler_menu_list.adapter=foodCardAdapter

        foodCardAdapter.submitList(data)      

       //make sure that the return view is one declared above up and is 
       //not the default 'inflater.inflate(R.layout.fragment_menu,         
       //container,false)' created by the ide

        return rootview    
    }

这些行必须在OnCreate中:

mmAdapter = new Adapter(msgList);
mrecyclerView.setAdapter(mmAdapter);

ArtistArrayAdapter adapter = new ArtistArrayAdapter(this, artists);
recyclerView = (RecyclerView) findViewById(R.id.cardList);
recyclerView.setHasFixedSize(true);
recyclerView.setLayoutManager(new LinearLayoutManager(this));
recyclerView.setAdapter(adapter);

只要用这个替换上面的代码，它就应该工作了。你所做的错误是在调用布局管理器之前调用了setAdapter(适配器)。

当你在创建阶段没有设置适配器时，会发生这种情况:

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity);
    mRecyclerView.setLayoutManager(new LinearLayoutManager(this));
    ....
}

public void onResume() {
    super.onResume();
    mRecyclerView.setAdapter(mAdapter);
    ....
}

只需移动设置适配器到onCreate与一个空数据，当你有数据调用:

mAdapter.notifyDataSetChanged();

在Kotlin，我们遇到了一个奇怪的不合逻辑的问题。

这并没有起作用:

 mBinding.serviceProviderCertificates.apply {
            adapter = adapter
            layoutManager =  LinearLayoutManager(activity)
        }

虽然这是有效的:

mBinding.serviceProviderCertificates.adapter = adapter
mBinding.serviceProviderCertificates.layoutManager = LinearLayoutManager(activity)

工作之余，我也会分享更多的真知灼见。