卡片视图未出现在 RecyclerView 中

Question

我正在构建一个连接到 REST API 并检索数据库中所有员工的应用程序。该应用程序使用 RecyclerView 显示在 CardView 中带回的所有员工。问题是 RecyclerView 中没有出现任何内容，并且有从 REST API 返回的数据。

它是一个 Android 应用程序，使用 Java 构建，操作系统使用 Pie。该项目是使用基本活动模板创建的。

我的活动课

public class ViewAllEmployees extends AppCompatActivity {

    private List<Employee> employees;

    private RecyclerView rcView;

    private EmployeeAdapter adapter;

    private Context context;

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_view_all_employees);

        Toolbar toolbar = findViewById(R.id.toolbar);

        setSupportActionBar(toolbar);

        context = this;

        getSupportActionBar().setDisplayHomeAsUpEnabled(true);

        FetchEmployeesTask async = new FetchEmployeesTask(new AsyncResponse() {

            @Override

            public void processFinished(List<Employee> output) {

                Log.i("Async", "Finished");

            }

        });

        async.execute();

        rcView = findViewById(R.id.rcView);

        adapter = new EmployeeAdapter(context, employees);

        rcView.setAdapter(adapter);

        rcView.setLayoutManager(new LinearLayoutManager(context));

    }

    private class FetchEmployeesTask extends AsyncTask<Void, Void, List<Employee>> {

        public AsyncResponse delegate = null;

        public  FetchEmployeesTask(AsyncResponse asyncResponse){

            delegate = asyncResponse;

        }

        @Override

        protected List<Employee> doInBackground(Void... voids) {

            return new APIHelper().fetchItems();

        }

        @Override

        protected void onPostExecute(List<Employee> items) {

            employees = items;

            delegate.processFinished(items);

        }

    }

    public interface AsyncResponse{

        void processFinished(List<Employee> output);

    }

Answer 1

您必须在填充阵列列表后通知您的适配器。初始化您的员工数组列表变量，然后执行：private class FetchEmployeesTask extends AsyncTask<Void, Void, List<Employee>> {&nbsp; &nbsp; public AsyncResponse delegate = null;&nbsp; &nbsp; public&nbsp; FetchEmployeesTask(AsyncResponse asyncResponse){&nbsp; &nbsp; &nbsp; &nbsp; delegate = asyncResponse;&nbsp; &nbsp; }&nbsp; &nbsp; @Override&nbsp; &nbsp; protected List<Employee> doInBackground(Void... voids) {&nbsp; &nbsp; &nbsp; &nbsp; return new APIHelper().fetchItems();&nbsp; &nbsp; }&nbsp; &nbsp; @Override&nbsp; &nbsp; protected void onPostExecute(List<Employee> items) {&nbsp; &nbsp; &nbsp; &nbsp; employees.addAll(items);&nbsp; &nbsp; &nbsp; &nbsp; adapter.notifyDataSetChanged();&nbsp; &nbsp; &nbsp; &nbsp; delegate.processFinished(items);&nbsp; &nbsp; }}

Answer 2

FetchEmployeesTask async = new FetchEmployeesTask(new AsyncResponse() {&nbsp; &nbsp; @Override&nbsp; &nbsp; public void processFinished(List<Employee> output) {&nbsp; &nbsp; &nbsp; &nbsp; Log.i("Async", "Finished");&nbsp; &nbsp; &nbsp; &nbsp; employees.addAll(items);&nbsp; &nbsp; &nbsp; &nbsp; adapter.notifyDataSetChanged();&nbsp; &nbsp; }});