出现错误：尝试在空对象引用上调用虚拟方法“void androidx.recyclerview.widget.RecyclerView.setLayoutManager”

Question

面临的问题：

我尝试在 Recylerview 中添加值来显示数据

代码：

'''

  public void apiCallBackOverRideMethodObj(Response< Object > response, JSONObject objResponse, String method, int position, String success) throws JSONException, IOException {
        if (response != null) {
            JSONObject object = new JSONObject( new Gson().toJson( response.body() ) );
            System.out.println( "response : " + object );
            responsePojo = new Gson().fromJson( object.toString(), new TypeToken< ResponsePojo >() {
            }.getType() );
            if (responsePojo.getItemData() != null) {
                itemData.clear();
                itemData.addAll( responsePojo.getItemData() );
                for (int i = 0; i < itemData.size(); i++) {
                    itemlist.add( datalist.get( i ).getItemName() );
                    ArrayAdapter< String > adapter = new ArrayAdapter<>( MaterialDetails.this, R.layout.spinner_item, itemlist );
                    spinner.setAdapter( adapter );
                }
            }
        }
    }
'''
I am facing error in below Recylerview Lines

'''
      recyclerView = findViewById( R.id.recycler_view_data );
        materialAdapter = new MaterialAdapter( this, datalist );
        recyclerView.setLayoutManager( new LinearLayoutManager( MaterialDetails.this ) );
        recyclerView.setAdapter( materialAdapter );

'''

如果有人有同样的问题请提出！！

Answer 1

recyclerView = findViewById( R.id.recycler_view_data );
        materialAdapter = new MaterialAdapter( this, datalist );
        recyclerView.setLayoutManager( new LinearLayoutManager( MaterialDetails.this ) );
        recyclerView.setAdapter( materialAdapter );

在fragment的onViewCreated()或Activity的onCreate()中调用上面的代码。