Question

我有一个简单的应用程序，其中显示了电影列表。当用户单击一个按钮时，它应该刷新列表，这意味着再次转到翻新并获取新列表。问题是，此刷新无效。当我打开应用程序时，它只会获取一次列表。

public class MoviesViewModel extends AndroidViewModel {
    private MutableLiveData<Resource<List<Movie>>> mLastdMovieListObservable;
    private Repository mRepository;

    public MoviesViewModel(Application application) {
        super(application);
        mRepository = new Repository();
    }

    public LiveData<Resource<List<Movie>>> getMovieListLiveData() {
        if (mLastdMovieListObservable == null) {
            mLastdMovieListObservable = mRepository.getMovieList();
        }
        return mLastdMovieListObservable;
    }
}

和存储库：

public MutableLiveData<Resource<List<Movie>>> getMovieList() {
    final MutableLiveData<Resource<List<Movie>>> data = new MutableLiveData<>();
    data.setValue(Resource.loading(null));

    mInterface.getMovies(.....).enqueue(new Callback<MovieListResponse>() {
        @Override
        public void onResponse(Call<MovieListResponse> call, Response<MovieListResponse> response) {
            if (response.isSuccessful()) {
                data.postValue(Resource.success(response.body().getResult()));
            } else {
                data.postValue(Resource.error(response.message(), null));
            }
        }
        @Override
        public void onFailure(Call<MovieListResponse> call, Throwable t) {
            data.postValue(Resource.error(t.getMessage(), null));
        }
    });

    return data;
}

然后在片段中只是：

mMoviesViewModel.getMovieListLiveData().observe(this, moviesResource -> {
    if (moviesResource.status == Status.SUCCESS) {
       .....
       .....

然后单击按钮部分，当我需要再次获取列表时，我不确定如何实现它。我尝试的任何方法均无效。存储库立即将数据返回为null。

Answer 1

您可以使用重试方法，并且我快速更改了代码以获取重试示例，并检查此源以获取更好的代码。LINK

Transformations.switchMap侦听重试，当它更改时，将再次调用swithMap。并且在UI ViewModel中应按如下所示进行配置，但在按钮中您只需调用重试即可。

mMoviesViewModel.getMovieListLiveData().observe(this, moviesResource -> {
if (moviesResource.status == Status.SUCCESS) {
   .....
   .....

在按钮上：

mMoviesViewModel.retry()

还有ViewModel：

public class MoviesViewModel extends AndroidViewModel {
private MutableLiveData<Resource<List<Movie>>> mLastdMovieListObservable;
private Repository mRepository;
private Boolean mRetry = false;

public MoviesViewModel(Application application) {
    super(application);
    mRepository = new Repository();
    mLastdMovieListObservable = Transformations.switchMap(mRetry){
        mLastdMovieListObservable = mRepository.getMovieList()
    }
}

public LiveData<Resource<List<Movie>>> getMovieListLiveData() {
    return mLastdMovieListObservable;
}

public void retry(){
    mRetry.setValue(true)
}}

Answer 2

电影类型的更改如下：

public class MoviesViewModel extends AndroidViewModel {
private MutableLiveData<Resource<List<Movie>>> mLastdMovieListObservable;
private Repository mRepository;
private Int mMovieType = 0;

public MoviesViewModel(Application application) {
    super(application);
    mRepository = new Repository();
    mLastdMovieListObservable = Transformations.switchMap(mMovieType, type->
        mLastdMovieListObservable = mRepository.getMovieList(type)
    );
}

public LiveData<Resource<List<Movie>>> getMovieListLiveData() {
    return mLastdMovieListObservable;
}

public void setMovieType(Int movieType){
    mMovieType.setValue(movieType)
}

}

使用翻新请求响应刷新实时数据

2 个答案: