Question

所以我有一个奇怪的情况。我实现了一个具有单个活动和两个片段的应用程序。两个片段都有一个过滤器选项，可以在其中选择一个类别。

基于类别，当前片段将使用新类别刷新和获取数据。

我正在使用ViewModel来获取数据，并使用LiveData来观察更改。

When a button is clicked in the Activity class, this method is called:
public static void replaceFragment(Activity activity,
                                       int navId,
                                       int selectedPosition) {
        Bundle bundle = new Bundle();
        bundle.putInt(INTENT_CATEGORY, selectedPosition);
        Navigation.findNavController(activity, R.id.fragment_nav_host)
                .navigate(navId, bundle, new NavOptions.Builder()
                        .setEnterAnim(R.anim.flip_right_in)
                        .setExitAnim(R.anim.flip_right_out)
                        .setPopEnterAnim(R.anim.flip_left_in)
                        .setPopExitAnim(R.anim.flip_left_out)
                        .build());
    }

我正在使用导航组件。所以奇怪的问题是，当我刷新片段时，LiveData被多次调用。我了解到，重新创建或刷新片段时，viewModel实例仍然相同。但不确定为什么会发生此问题。

如果有人可以帮助解决此问题，将不胜感激。

可以找到整个应用代码here

更新：因此，如果我从以下位置更改InitializeViewModel（）方法：

private void initialiseViewModel() {
    moviesListViewModel = ViewModelProviders.of(this, viewModelFactory).get(MovieListViewModel.class);
    moviesListViewModel.fetchMovies(MENU_MOVIE_ITEM.get(getArguments() == null ? 0: getArguments().getInt(INTENT_CATEGORY)));
    moviesListViewModel.getMoviesLiveData().observe(this, resource -> {
        if(resource.isLoading()) {
            displayLoader();

        } else if(resource.data != null && !resource.data.isEmpty()) {
            handleSuccessResponse(resource.data);

        } else handleErrorResponse();
    });
}

TO

    private void initialiseViewModel() {

        AppDatabase appDatabase = Room.databaseBuilder(getContext(),
                AppDatabase.class, "Entertainment.db")
                .allowMainThreadQueries().build();

        HttpLoggingInterceptor logging = new HttpLoggingInterceptor();
        logging.setLevel(HttpLoggingInterceptor.Level.BODY);

        OkHttpClient.Builder httpClient = new OkHttpClient.Builder();
        httpClient.addInterceptor(logging);
        httpClient.addNetworkInterceptor(new RequestInterceptor());
        httpClient.connectTimeout(30, TimeUnit.SECONDS);
        httpClient.readTimeout(30, TimeUnit.SECONDS);

        MovieApiService movieApiService =
                new Retrofit.Builder()
                        .addConverterFactory(GsonConverterFactory.create(new GsonBuilder().create()))
                        .addCallAdapterFactory(RxJava2CallAdapterFactory.create())
                        .baseUrl(BASE_URL)
                        .client(httpClient.build())
                        .build().create(MovieApiService.class);

//        moviesListViewModel = ViewModelProviders.of(this, viewModelFactory).get(MovieListViewModel.class);
        moviesListViewModel = new MovieListViewModel(appDatabase.movieDao(), movieApiService);
        moviesListViewModel.fetchMovies(MENU_MOVIE_ITEM.get(getArguments() == null ? 0: getArguments().getInt(INTENT_CATEGORY)));
        moviesListViewModel.getMoviesLiveData().observe(this, resource -> {
            if(resource.isLoading()) {
                displayLoader();

            } else if(resource.data != null && !resource.data.isEmpty()) {
                handleSuccessResponse(resource.data);

            } else handleErrorResponse();
        });
    }

然后问题似乎消失了：(。关于为什么的任何指针？

Android-刷新片段时不会取消订阅LiveData

0 个答案: