当我单击按钮时，我的列表没有显示

Question

实际上，我在这里找不到任何错误。我想我在这里错过了一些东西。该过滤器按钮不起作用。您的帮助将不胜感激。谢谢

这是我的片段。类

    sortByLeastExpensive = rootView.findViewById(R.id.sort_by_least_expensive);
    sortByMostExpensive = rootView.findViewById(R.id.sort_by_most_expensive);
    sortByMostRecent = rootView.findViewById(R.id.sort_by_most_recent);

    applyFiltersBtn = rootView.findViewById(R.id.apply_filters_btn);

    sortByLeastExpensive.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            //set the filter; or call the viewmodel to set the filter?
           mViewModel.sortBy.setValue(getResources().getString(R.string.sort_rooms_ascending));
        }
    });
    sortByMostExpensive.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            mViewModel.sortBy.setValue(getResources().getString(R.string.sort_rooms_descending));
        }
    });
    sortByMostRecent.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
          mViewModel.sortBy.setValue("sort_most_recent");
       }
    });


    return rootView;
}


@RequiresApi(api = Build.VERSION_CODES.O)
@Override
public void onActivityCreated(@Nullable Bundle savedInstanceState) {
    super.onActivityCreated(savedInstanceState);
    mViewModel = ViewModelProviders.of(getActivity()).get(FilterRoomsViewModel.class);

  mViewModel.getSortBy().observe(this, Observer -> {
        Log.i("Viewmodel", "Viewmodel ,sortby: " + mViewModel.sortBy.getValue());
    });


    applyFiltersBtn.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
           FilterRoomsRepository roomsRepository = new FilterRoomsRepository();
           roomsRepository.getFilteredRooms(mViewModel.sortBy.getValue());
           
        }
   });
}

这是viewmodel.class

我已经更新了我的viewmodel.class。现在，它向我显示了fragment.class的另一个错误

public FilterRoomsViewModel(Application application){
    super();

FilterRoomsRepository filterRoomsRepository = new FilterRoomsRepository(application);
}
public MutableLiveData<String> getRooms(){
    if (rooms==null){
        rooms = new MutableLiveData<String>();
    }
return rooms;
}
    public LiveData<String> getSortBy() {
if (sortBy == null){
    sortBy = new MutableLiveData<String>();
}
    return sortBy;
} 

这是repository.class

    if(sortyBy.equals("ascending")){
        Log.i("Sort by", "Rooms sorted in ascending order");
        filterQuery.orderByAscending("roomRentalAmount");
    }else if (sortyBy.equals("descending")){
        Log.i("Sort by", "Rooms sorted in descending order");
        filterQuery.orderByDescending("roomRentalAmount");
    }else {
        filterQuery.orderByDescending("updatedAt");
    }

    filterQuery.findInBackground(new FindCallback<ParseObject>() {
        @Override
        public void done(List<ParseObject> objects, ParseException e) {
            if(e == null){
                //success
                Log.i("Rooms", "Filtered rooms, " + objects.get(0).getObjectId());
                rooms.setValue(objects);
            }else{
                //error, handle accordingly
                Log.e("Error", "Error filtering, " + e.getMessage());
            }
        }
    });
    Log.i("Rooms", "Live data rooms, " + rooms.getValue());
    return rooms;
}

Answer 1

它不显示什么意思？它没有显示在ui或日志中吗？因为当您调用getFilteredRooms时，对结果不执行任何操作。 我的建议是将存储库调用移至viewModel，以便与其在片段中调用getFilteredRooms，而不是像viewModel.getFilteredRooms这样调用sth，然后在viewModel中调用存储库，然后使用结果进行设置实时数据的价值。 然后，在片段中，您只需要观察此变量，然后根据该变量更新ui。通过这样做，您可以将逻辑（视图模型和存储库）与ui部件（片段）分开。

这是一个很好的教程，介绍如何使用mvvm模式进行编码：https://medium.com/@er.ankitbisht/mvvm-model-view-viewmodel-kotlin-google-jetpack-f02ec7754854