基于用户输入的过滤器-LiveData，Recycler，RoomView

Question

我有一个用于Android应用程序的SQLite数据库。数据库在每个属性中都有一个用于[[properties的table和另一个用于repairs的表。

表维修

：

@Entity(tableName = "repairs",
        indices = {@Index(value = "repairID", unique = true), @Index("repairPropID")})

public class MYRepairs
{
    @PrimaryKey(autoGenerate = true)
    @ColumnInfo(name = "repid")
    public int id;

    @ColumnInfo(name = "repairID")
    @NonNull
    public String repairID;

    @ColumnInfo(name = "repairPropID")
    public int repairPropID;
}

...
然后是
RepairsDao.java

 @Dao
    public interface MyRepairsDao
    {
        @Query("SELECT * FROM repairs WHERE repid = :repid LIMIT 1")
        MYRepairs findRepairById(String repid);


        @Query("SELECT * FROM repairs WHERE repairPropID = :repairPropID")
        MYRepairs findRepairByPropID(int repairPropID);


        @Query("SELECT * FROM repairs ORDER BY repairPropID ASC")
        LiveData<List<MYRepairs>> getAllRepairs();

 @Query("SELECT * FROM repairs WHERE repairPropID = :repairPropID")
    LiveData<List<MYRepairs>> getPropertyRepairs(int repairPropID);

    }

在
ViewModel

：中

   public class repairViewModel extends AndroidViewModel
    {
        private MyRepairsDao myRepairDao;
        private LiveData<List<MYRepairs>> repairLiveData;
        private LiveData<List<MYRepairs>> repairPropertyLiveData;
        private LiveData<String> filterLiveData = new MutableLiveData<String>();

        public repairViewModel(@NonNull Application application)
        {
            super(application);
            myRepairDao = DogwoodDatabase.getDatabase(application).repairDao();
            repairLiveData = myRepairDao.getAllRepairs();
            repairPropertyLiveData = myRepairDao.getPropertyRepairs(propertyID);
        }

        public LiveData<List<MYRepairs>> getAllRepairs()
        {
            return repairLiveData;
        }

        public LiveData<List<MYRepairs>> getPropertyRepairs(int propertyID) 
        { 
            return repairPropertyLiveData; 
        }

并且在
RecyclerView.Adapter

：中

public class repairListAdapter extends RecyclerView.Adapter<repairListAdapter.RepairViewHolder>
{
@NonNull
        @Override
        public repairListAdapter.RepairViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType)
        {
            final View itemView = layoutInflater.inflate(R.layout.repaircontent, parent, false);
            return new repairListAdapter.RepairViewHolder(itemView);
        }

在
repairFragment

中-我们只想查看用户选择的属性的修复。 repairFragement接收到属性代码propertyID。 initData（（）是已知的

   public class repairFragment extends Fragment
    {

        private repairListAdapter repairListAdapter;
        private repairViewModel repairViewModel;

        public void onCreate(@Nullable Bundle savedInstanceState)
        {
            super.onCreate(savedInstanceState);
            propertyID = getArguments().getString("ARG_PROPNUM_ID");
            propNumID = Integer.parseInt(propertyID);
            initData();
        }



     private void initData()
        {
            Log.e ("INIT", "ID is " + propertyID);

            repairViewModel = new 
                   ViewModelProvider(this).get(repairViewModel.class);


repairViewModel.getPropertyRepairs(propertyID).observe(this, new Observer<List<MYRepairs>>()
            {
                @Override
                public void onChanged(@Nullable List<MYRepairs> MYRepairs)
                {
                    repairListAdapter.setMYRepairList(MYRepairs);
                }
            });

        }

此返回无记录。在理想的世界中，我的财产无法修复，但我不住在那个世界中！ 
我已搜寻此板寻求过滤方面的帮助。 
您能如何帮助我[仅修复用户选择的属性（propertyID）。 
感谢Rachael

Answer 1

在repairViewModel中：

public LiveData<List<MYRepairs>> getPropertyRepairs(int propertyID)
    {

        repairPropertyLiveData = myRepairDao.getPropertyRepairs(propertyID);
        return repairPropertyLiveData;
    }

Answer 2

public LiveData<List<MYRepairs>> getPropertyRepairs() { 
    return repairPropertyLiveData; 
}

和

private MutableLiveData<String> selectedPropertyId = new MutableLiveData<>();

private final repairPropertyLiveData = Transformations.switchMap(selectedPropertyId, (id) -> {
    return myRepairDao.getPropertyRepairs(id);
});

public void updateSelectedProperty(String propertyId) {
    selectedPropertyId.setValue(propertyId);
}

这样，您不会得到新的订阅，如果以后要选择其他属性ID，新订阅将不会被正确取消。