在LoadInitial回调之前调用LiveData上的观察者

Question

在我正在工作的一个项目中，我使用了paginglibrary和Reverfit。这是我第一次这么做。

数据正常返回。但是我注意到我的viewmodel（更确切地说是我的LiveData）中的观察者在我的PageKeyedDataSource中的LoadIsitial回调之前被调用。这将使传递给适配器的列表为空。为什么在我回调之前调用Observer？

public GameDataViewModel(){
        GameResponseDataSourceFactory gameResponseViewModelFactory = new GameResponseDataSourceFactory();
        gameListLiveData = gameResponseViewModelFactory.getGameResponseMutableLiveData();

        PagedList.Config config = (new PagedList.Config.Builder())
                .setEnablePlaceholders(false)
                .setPageSize(20)
                .build();

        gameList = new LivePagedListBuilder(gameResponseViewModelFactory, config).build();
    }

final GameListAdapter gameListAdapter = new GameListAdapter();

        GameDataViewModel gameDataViewModel = ViewModelProvider.AndroidViewModelFactory.
                getInstance(this.getApplication()).create(GameDataViewModel.class);

        gameDataViewModel.gameList.observe(this, new Observer<PagedList<GameResponse>>() {
            @Override
            public void onChanged(@Nullable PagedList<GameResponse> gameResponses) {
                gameListAdapter.submitList(gameResponses);
            }
        });

Call<GameListResponse> call = HttpConnectionHandler.getInstance().getTwitchGameApi().getTopGames(CLIENT_ID,  20, null,  null);
        call.enqueue(new Callback<GameListResponse>() {
            @Override
            public void onResponse(Call<GameListResponse> call, Response<GameListResponse> response) {
                //initialLoading.postValue(DataState.SUCCESS);
                //networkState.postValue(DataState.SUCCESS);
                if(response.code() == 200) {
                    GameListResponse gameListResponse = response.body();
                    callback.onResult(gameListResponse.getGamesList(), 0, gameListResponse.getGamesList().size(), null, gameListResponse.getCursor());
                }
                else{
                    try {
                        Log.e("ERROR", response.errorBody().string());
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                }
            }

Answer 1

我最大的愚蠢之处是覆盖getItemCount并返回零。除去它，一切正常。