无法将 List<Obj>从 Single<List<Obj>> 获取从 ViewModel 切换到 Activity RecyclerView 保持为空原因在哪里？

如何解决无法将 List<Obj>从 Single<List<Obj>> 获取从 ViewModel 切换到 Activity RecyclerView 保持为空原因在哪里？

在道中：

    @Query("SELECT * FROM person_table WHERE status = :statusname ORDER BY RANDOM() LIMIT 1")
Single<List<Person>> getGuyWho(String statusname);

在回购中：

public class PersonRepository {
    private Single<List<Person>> mGuyWho; 
    PersonRepository(Application application) {
        PersonRoomDatabase db = PersonRoomDatabase.getDatabase(application);        
        mPersonDao = db.PersonDao();
        mGuyWho = mPersonDao.getGuyWho("debil"); 
    }
    Single<List<Person>> getGuyWho() {
        return mGuyWho;
    }
}

在视图模型中：

public class PersonViewModel extends AndroidViewModel {
    private PersonRepository mRepository;
    CompositeDisposable composite = new CompositeDisposable();
    private Single<List<Person>> mGuyWho; 
    private List<Person> workList;
    public PersonViewModel(@NonNull Application application) {
        super(application);
        mRepository = new PersonRepository(application);
        workList = new ArrayList<>(); //initializing workList
        mGuyWho = mRepository.getGuyWho();

        mGuyWho.subscribeOn(Schedulers.io())
            .observeOn(AndroidSchedulers.mainThread())
            .subscribe(new SingleObserver<List<Person>>() {
                @Override
                public void onSubscribe(Disposable d) {
                    composite.add(d);
                }

                @Override
                public void onSuccess(List<Person> people) {
                    Log.d(TAG,"onSuccess: called");
                    workList.addAll(people);
                }

                @Override
                public void onError(Throwable e) {
                    Log.d(TAG,"onError: called");
                    Toast.makeText(application,"NO DATA",Toast.LENGTH_SHORT).show();
                }
            });
    }
    public List<Person> getWorkList() {
        return workList;
    }
}

В 活动：

public class MudakActivity extends AppCompatActivity implements CardStackListener {
    List<Person> debilList;
    private PersonViewModel debilViewModel;
    private CardStackView debilCardStackView;
    private MudakAdapter debilAdapter;
    //declaring variables

    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        debilAdapter = new DebilAdapter(new DebilAdapter.PersonDiff(),debilList); 
        debilCardStackView.setLayoutManager(debilCardStackLayoutManager);
        debilCardStackView.setAdapter(debilAdapter);
        //initializing other variables
        debilViewModel = new ViewModelProvider(this,ViewModelProvider.AndroidViewModelFactory.getInstance(this.getApplication()))
                .get(PersonViewModel.class);
        debilList = debilViewModel.getWorkList();
    }
}

recyclerView (cardStackView) 显示为空，尽管具有“debil”状态名称的对象肯定存在（当我使用 LiveData 调用它们时，它们会显示在视图中）。我想我在 ViewModel 中输入了错误的内容，可能不是在适当的地方。找不到。错误可能在哪里以及如何解决？

解决方法

workList 之后会发生变化，并且您在它更新之前正在使用它。最好将 workList 设为 LiveData 并观察变化。当数据设置为列表时，您必须通知适配器进行更改。

public class PersonViewModel extends AndroidViewModel {
    private PersonRepository mRepository;
    CompositeDisposable composite = new CompositeDisposable();
    private Single<List<Person>> mGuyWho;
    public LiveData<List<Person>> workList = new MutableLiveData<>();
    public PersonViewModel(@NonNull Application application) {
        super(application);
        mRepository = new PersonRepository(application);
        workList = new ArrayList<>(); //initializing workList
        mGuyWho = mRepository.getGuyWho();
        mGuyWho.subscribeOn(Schedulers.io())
                .observeOn(AndroidSchedulers.mainThread())
                .subscribe(new SingleObserver<List<Person>>() {
                    @Override
                    public void onSubscribe(Disposable d) {
                        composite.add(d);
                    }
                    @Override
                    public void onSuccess(List<Person> people) {
                        workList.setValue(people);
                    }
                    @Override
                    public void onError(Throwable e) { }
                });
    }
}

观察组件中的 LiveData。

debilViewModel.workList.observe(this,(Observer<List<Person>>) personList -> {
        debilAdapter.submitList(personList);
    });