Java 如何使用房间数据库使进度条影响UI上的数据？

我使用的是一个SQLite数据库。我希望SeekBar的进度能够影响用户界面上检索/显示的数据。我提出了以下解决方案，但担心它不可扩展。我认为，如果seekbar的progress值能够查询数据库本身并返回数据，而不是遍历所有检索到的数据，排除或包含给定条件的数据，那就更好了

public class DetailsFirstTabFragment extends Fragment {

    private DetailsFirstTabViewModel viewModel;
    private RecyclerView recentThings;
    private TextView progressTextView;
    final RecentThings adapter = new RecentThings();
    private List<ThingEntity> thingEntities;

    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        viewModel =
                ViewModelProviders.of(this).get(DetailsFirstTabViewModel.class);
    }

    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container,
                             @Nullable Bundle savedInstanceState) {

        View root = inflater.inflate(R.layout.fragment_first_page_expense_details, container, false);

        recentThings = root.findViewById(R.id.recycler_view_recent_things);
        recentThings.setLayoutManager(new LinearLayoutManager(getContext()));
        recentThings.setHasFixedSize(true);

        recentThings.setAdapter(adapter);

        final float[] totalSum = {0};
        final TextView textViewTotalSum = root.findViewById(R.id.textViewStuffTotalSum);

        SeekBar seekBar = root.findViewById(R.id.seekBarStuffDetails);
        seekBar.setOnSeekBarChangeListener(seekBarChangeListener);

        progressTextView = root.findViewById(R.id.textViewProgress);

        viewModel.getAllThings().observe(this, new Observer<List<ThingEntity>>() {
// I wonder if the progress bar value could be passed here to call my repository
            @Override
            public void onChanged(List<ThingEntity> thingEntities) {
                for (ThingEntity thing : thingEntities) {
                    totalSum[0] = totalSum[0] + thing.getThingAmount();
                }
                textViewTotalSum.setText(String.valueOf(totalSum[0]));
                adapter.setThingEntityList(thingEntities);
                setThingEntities(thingEntities);
            }
        });
        return root;
    }

    @Override
    public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
        Bundle args = getArguments();
    }

    public void setThingEntities(List<ThingsEntity> thingEntities) {
        this.thingEntities = thingEntities;
    }
    SeekBar.OnSeekBarChangeListener seekBarChangeListener = new SeekBar.OnSeekBarChangeListener() {
        int progressValue = 0;

        @Override
        public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {
            String progressText = "Date " + String.valueOf(progress);
            progressValue = progress;
            progressTextView.setText(progressText);
        }

        @Override
        public void onStartTrackingTouch(SeekBar seekBar) {

        }

        @Override
        public void onStopTrackingTouch(SeekBar seekBar) {
// this is the current implementation. It simply loops over every thing queried from database and sends the result to the adapter for drawing on the UI.
            List<ThingEntity> shownThings = new ArrayList<>();
            for (ThingEntity entity : thingEntities) {
                if (entity.getThingAmount() > progressValue) {
                    shownThings.add(entity);
                }
            }
            adapter.setThingEntityList(shownThings);
        }
    };
}

---

将您的

dao

的

getAllThings

更改为接受参数

@Query("SELECT * FROM things_table WHERE thingAmount >:minValue ORDER BY thingDate ASC")
LiveData<List<ThingEntity>> getAllThings(int minValue);

public class DetailsFirstTabViewModel extends AndroidViewModel {
    private MutableLiveData<List<ThingEntity>> things = new MutableLiveData<>();

    ...

    public MutableLiveData<List<ThingEntity>> getThings() {
        return things;
    }

    public void getAllThings(int minValue) {
        things.postValue(repository.getAllThings(minValue).getValue());
    }
}

并通过

onStopTrackingTouch

调用

progressValue

@Override
public void onStopTrackingTouch(SeekBar seekBar) {

    //Just call to fetch content with progressValue and update adapter inside onChanged
    viewModel.getAllThings(progressValue);
}

---

添加您的

viewModel

和

Dao

implementation@Md.Asaduzzaman添加了viewModel和Dao。应该可以正常工作。在查询中未发现任何问题。您是否也可以发布

ThingEntity

和

存储库

？

public LiveData<List<ThingEntity>> getSpecifiedThings(int minValue) {
    specifiedThings = thingDao.getSpecificThings(minValue);
    Log.d(TAG, "getSpecifiedThings: " + specifiedThings.getValue()); // returns null
    return specifiedThings;
}

private MutableLiveData<List<ThingEntity>> thingsList = new MutableLiveData<>();

public MutableLiveData<List<ThingEntity>> getThingsList() {
    return thingsList;
}

public void getSpecifiedThings(int minValue) {
    thingsList.postValue(repository.getSpecifiedThings(minValue).getValue());
}

public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container,
                             @Nullable Bundle savedInstanceState) {

        ....

        Log.d(TAG, "onStopTrackingTouch: " + viewModel.getAllThings().getValue()); // returns null
        viewModel.getSpecifiedThings(1); //this should retrieve every entity in my database

        viewModel.getThingsList().observe(this, new Observer<List<ThingEntity>>() {
            @Override
            public void onChanged(List<ThingEntity> thingEntities) {
                if (thingEntities != null) { // returns null
                    adapter.setThingEntityList(thingEntities);
                }
                Log.d(TAG, "onChanged: " + thingEntities); // returns null
            }
        });
    ....
}

@Entity(tableName = "things_table")
public class ThingEntity {
    @PrimaryKey(autoGenerate = true)
    private int id;

    private Date thingDate;
    private float thingAmount;
    private String classification;
    private String category;
    private String subcategory;
    private String placeName;
    private int placeCode;

    public ThingEntity(Date thingDate, float thingAmount, String classification,
                             String category, String subcategory, String placeName, int placeCode) {
        this.thingDate = thingDate;
        this.thingAmount = thingAmount;
        this.classification = classification;
        this.category = category;
        this.subcategory = subcategory;
        this.placeName = placeName;
        this.placeCode = placeCode;
    }

    public void setId(int id) {
        this.id = id;
    }

    public int getId() {
        return id;
    }

    public Date getThingDate() {
        return thingDate;
    }

    public float getThingAmount() {
        return thingAmount;
    }

    public String getClassification() {
        return classification;
    }

    public String getCategory() {
        return category;
    }

    public String getSubcategory() {
        return subcategory;
    }

    public String getPlaceName() {
        return placeName;
    }

    public int getPlaceCode() {
        return placeCode;
    }
}

@Query("SELECT * FROM things_table WHERE thingAmount >:minValue ORDER BY thingDate ASC")
LiveData<List<ThingEntity>> getAllThings(int minValue);

public class DetailsFirstTabViewModel extends AndroidViewModel {
    private MutableLiveData<List<ThingEntity>> things = new MutableLiveData<>();

    ...

    public MutableLiveData<List<ThingEntity>> getThings() {
        return things;
    }

    public void getAllThings(int minValue) {
        things.postValue(repository.getAllThings(minValue).getValue());
    }
}

@Override
public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container,
                         @Nullable Bundle savedInstanceState) {

    View root = inflater.inflate(R.layout.fragment_first_page_expense_details, container, false);

    ....

    //Observe things and update data accordingly 
    viewModel.getThings().observe(this, new Observer<List<ThingEntity>>() {
        // I wonder if the progress bar value could be passed here to call my repository
        @Override
        public void onChanged(List<ThingEntity> thingEntities) {

            //check null here and skip
            if(thingEntities != null) {
                for (ThingEntity thing : thingEntities) {
                    totalSum[0] = totalSum[0] + thing.getThingAmount();
                }
                textViewTotalSum.setText(String.valueOf(totalSum[0]));
                adapter.setThingEntityList(thingEntities);
                setThingEntities(thingEntities);
            }
        }
    });

    //Initially call with default min 0
    viewModel.getAllThings(0);

    return root;
}

@Override
public void onStopTrackingTouch(SeekBar seekBar) {

    //Just call to fetch content with progressValue and update adapter inside onChanged
    viewModel.getAllThings(progressValue);
}