ViewModel /存储库显示为空白

如何解决ViewModel /存储库显示为空白

我正在遵循Github Browser app tutorial来构建我的项目而不使用数据绑定。显示只是空白，仅显示导航视图。我无法弄清楚哪里出了问题。我尝试调试，所有显示的结果都是null。没有错误。

ViewModel.java：

env NODE_ENV=test jest

Repository.java：

public class ListViewModel extends ViewModel {
    private final LiveData<Resource<List<Something>>> repositories;
    private int langID;
    private int categoryID;
    private MutableLiveData<List<Something>> networkInfoObservable = new MutableLiveData<>();
    private static String TAG = "SomethingViewModel";

    @SuppressWarnings("unchecked")
    @Inject
    public ListViewModel(ListRepository listRepository) {
        repositories = Transformations.switchMap(networkInfoObservable,someList ->
                listRepository.loadList(2,1)); // hard-coding values to test)

    }


    @VisibleForTesting
    public void setListArgs(int langID,int categoryID) {
        this.langID = langID;
        this.categoryID = categoryID;
    }

    @VisibleForTesting
    public LiveData<Resource<List<Something>>> getList() {
        return repositories;
    }

}

DAO.java：

@Singleton
public class ListRepository {
    private final SomeDao someDao;
    private final SomeService someService;
    private final AppExecutors appExecutors;
    private static String TAG = "LIST_REPOSITORY";

    @Inject
    ListRepository(AppExecutors appExecutors,SomeDao someDao,SomeService someService) {
        this.someDao = someDao;
        this.someService = someService;
        this.appExecutors = appExecutors;
    }

    public LiveData<Resource<List<Something>>> loadList(int langId,int categoryID) {
        return new NetworkBoundResource<List<Something>,ListWrapper<Something>>(appExecutors) {
            @Override
            protected void saveCallResult(@NonNull ListWrapper<Something> item) {
                for (Something someItem : item.someItems){
                    someItem.lang_id = langId;
                    someItem.cat_id = categoryID;
                    someDao.insertList(someItem);
                }
            }

            @Override
            protected boolean shouldFetch(@Nullable List<Something> data) {
                return data == null;
            }

            @NonNull
            @Override
            protected LiveData<List<Something>> loadFromDb() {
                return someDao.getList(langId,categoryID);
            }

            @NonNull
            @Override
            protected LiveData<ApiResponse<ListWrapper<Something>>> createCall() {
                Log.d(TAG,"Test");
                return someService.getList(langId,categoryID);
            }
        }.asLiveData();
    }
}

APIService.java：

@Dao
public interface SomeDao {
    @Insert(onConflict = OnConflictStrategy.REPLACE)
    public void insertList(Something someList);

    @Query("SELECT * FROM list WHERE langId=:langId AND catId=:catId")
    public LiveData<List<Something>> getList(int langId,int catId);
}

BaseFragment：

public interface SomeService {

        @POST("/getCategoryItem")
        LiveData<ApiResponse<ListWrapper<Something>>> getList(@Query("langId") Integer langId,@Query("catId") Integer category);

}

解决方法

我做了一些研究，发现必须实现一个内部静态类来更新参数：

public class ListViewModel extends ViewModel {
    private final LiveData<Resource<List<Something>>> repositories;
    private final MutableLiveData<ListArgs> listArgs;
    private static String TAG = "SomethingViewModel";

    @SuppressWarnings("unchecked")
    @Inject
    public ListViewModel(ListRepository listRepository) {
       this.listArgs = new MutableLiveData<>();
        repositories = Transformations.switchMap(listArgs,listArg ->
                listRepository.loadList(listArg.langID,listArg.categoryID)); 

    }


     @VisibleForTesting
    public void setListArgs(int langID,int categoryID) {
        ListArgs update = new ListArgs(langID,categoryID);
        if (Objects.equals(listArgs.getValue(),update)) {
            return;
        }
        listArgs.setValue(update);
    }

    @VisibleForTesting
    public LiveData<Resource<List<Something>>> getList() {
        return repositories;
    }

    static class ListArgs {
        final int langID;
        final int categoryID;

        ListArgs(int langID,int categoryID) {
            this.langID = langID;
            this.categoryID = categoryID;
        }
    }



}

,

您的代码是在不创建实例的抽象类内部实现的，因此尚未被调用