使用 livedata 的 Recyclerview 在数据更改后不更新。只有在我旋转屏幕后

Question

我有一个天气应用程序，允许用户保存位置（存储在本地的房间数据库中）并显示所述位置的天气。当用户将城市添加到数据库时，我执行天气 API 调用，然后使用所需信息将城市添加到数据库中。

public class InsertSingleCityWorker extends Worker {

private MyCitiesDatabase citiesDatabase;
private String nickname;
private int zip;

private static final String TAG = "APICallsWorker";


public InsertSingleCityWorker(@NonNull Context context, @NonNull WorkerParameters workerParams) {
    super(context, workerParams);
    citiesDatabase = MyCitiesDatabase.getInstance(getApplicationContext());
    Log.d(TAG, "APICallsWorker: WORK CREATED");
}

@NonNull
@Override
public Result doWork() {
    nickname = getInputData().getString("nickname");
    zip = getInputData().getInt("zip", -1);
    performAPICalls();
    return Result.success();
}

private void performAPICalls() {
    WeatherApi weatherApi = RetrofitService.createService(WeatherApi.class);
    weatherApi.getWeatherWithZip(zip, Constants.API_KEY).enqueue(new Callback<WeatherResponse>() {
        @Override
        public void onResponse(Call<WeatherResponse> call, Response<WeatherResponse> response) {
            if(response.isSuccessful()){
                if(response.body() != null){
                    handleAPIResult(response.body());
                }
            } else{
                Toast.makeText(getApplicationContext(), "Please Enter a valid zip", Toast.LENGTH_SHORT).show();
            }
        }
        @Override
        public void onFailure(Call<WeatherResponse> call, Throwable t) {
            handleError(t);
        }
    });
}

private void handleAPIResult(WeatherResponse weatherResponse) {
    Log.d(TAG, "handleAPIResult: HERE");
    Completable.fromAction(() -> {
        String timestamp = StringManipulation.getCurrentTimestamp();
        int temperature = Integer.valueOf(Conversions.kelvinToFahrenheit(weatherResponse.getMain().getTemp()));
        String locationName = weatherResponse.getName();
        int windSpeed = Math.round(weatherResponse.getWind().getSpeed());
        int humidity = Math.round(weatherResponse.getMain().getHumidity());

        MyCity city = new MyCity(nickname, zip, timestamp, temperature, locationName, windSpeed, humidity);
        citiesDatabase.myCitiesDao().insert(city);
    }).observeOn(AndroidSchedulers.mainThread())
            .subscribeOn(Schedulers.io())
            .subscribe();
}

private void handleError(Throwable t) {
    Log.d(TAG, "handleError: ERROR: " + t.getMessage());
}

}

现在我在 UI 中有一个按钮可以一次更新所有城市（最终我希望它是一个简单的向下滚动来更新或类似的东西）。问题是，当我单击更新所有城市时，工作已执行但 recyclerview 未更新（因为未将新数据传递给它）但如果我更改配置（如旋转屏幕），新数据将显示。

这是我的主要课程：

public class MainActivity extends AppCompatActivity implements AddCityDialog.AddCityDialogListener {

    private static final String TAG = "MainActivity";

    //Widgets
    private Button mAddNewCity;

    private RecyclerView mRecyclerView;
    private WeatherRecyclerAdapter mRecyclerAdapter;

    private ViewAddDeleteCitiesViewModel mViewDeleteViewModel;
    private ViewAddDeleteCitiesViewModelFactory mViewDeleteMyCitiesViewModelFactory;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        initWidgets();
        initViewModel();
        initRecyclerView();
        setupListeners();
    }


    public void initWidgets() {
        mAddNewCity = findViewById(R.id.btn_add_new_city);
    }

    public void initViewModel() {
        mViewDeleteMyCitiesViewModelFactory = new ViewAddDeleteCitiesViewModelFactory(this.getApplication());
        mViewDeleteViewModel = new ViewModelProvider(this, mViewDeleteMyCitiesViewModelFactory).get(ViewAddDeleteCitiesViewModel.class);

        mViewDeleteViewModel.observeAllCities().observe(this, cities -> mRecyclerAdapter.submitList(cities));
    }


    public void setupListeners() {
        mAddNewCity.setOnClickListener(v -> addCityDialog());

        mRecyclerAdapter.setOnItemClickListener(myCity -> Toast.makeText(MainActivity.this, "Item Clicked: ", Toast.LENGTH_SHORT).show());

        new ItemTouchHelper(new ItemTouchHelper.SimpleCallback(0, ItemTouchHelper.LEFT) {
            @Override
            public boolean onMove(@NonNull RecyclerView recyclerView, @NonNull RecyclerView.ViewHolder viewHolder, @NonNull RecyclerView.ViewHolder target) {
                return false;
            }

            @Override
            public void onSwiped(@NonNull RecyclerView.ViewHolder viewHolder, int direction) {
                mViewDeleteViewModel.delete(mRecyclerAdapter.getCityAt(viewHolder.getAdapterPosition()));
                Log.d(TAG, "onSwiped: Deleted");
            }
        }).attachToRecyclerView(mRecyclerView);
    }

    public void addCityDialog() {
        AddCityDialog addCityDialog = new AddCityDialog();
        addCityDialog.show(getSupportFragmentManager(), "Add City Dialog");
    }

    public void initRecyclerView() {
        mRecyclerView = findViewById(R.id.recycler_view);
        mRecyclerAdapter = new WeatherRecyclerAdapter();
        mRecyclerView.setAdapter(mRecyclerAdapter);
        mRecyclerView.setLayoutManager(new LinearLayoutManager(this));
        Log.d(TAG, "initRecyclerView: Recycler View Initialized");
    }

    /**
     * Uses information (@param nickname @param zip) from Dialog to add a new city to the room db
     * by passing the input to the one time worker class.
     * @param nickname
     * @param zip
     */
    @Override
    public void addCity(String nickname, String zip) {
        insertSingleCity(nickname, Integer.valueOf(zip));
        Log.d(TAG, "addCity: CITY ADDED MAIN ACTIVITY");

        updateAllCities(mViewDeleteViewModel.getAllCities());
    }

    public void insertSingleCity(String nickname, int zip) {
        OneTimeWorkRequest oneTimeWorkRequest = new OneTimeWorkRequest.Builder(InsertSingleCityWorker.class)
                .setInputData(DataManipulation.createInputData(nickname, zip))
                .build();

        WorkManager.getInstance(this).enqueue(oneTimeWorkRequest);
    }


    public void updateCities(View v){
        updateAllCities(mViewDeleteViewModel.getAllCities());
    }


    //Stars work to get API when a city is added
    private void updateAllCities(List<MyCity> cities) {
        Log.d(TAG, "startWork: here");
        for (MyCity city : cities) {
            OneTimeWorkRequest oneTimeWorkRequest = new OneTimeWorkRequest.Builder(UpdateAllCitiesWorker.class)
                    .setInputData(DataManipulation.createInputData(city.getId(), city.getNickname(), city.getZipCode()))
                    .build();

            WorkManager.getInstance(this).enqueue(oneTimeWorkRequest);
            Log.d(TAG, "startWork: WORK ENQUEUED");
        }
    }
}

更新所有城市工作者：

    public UpdateAllCitiesWorker(@NonNull Context context, @NonNull WorkerParameters workerParams) {
    super(context, workerParams);
    citiesDatabase = MyCitiesDatabase.getInstance(getApplicationContext());
    Log.d(TAG, "APICallsWorker: WORK CREATED");
}

@NonNull
@Override
public Result doWork() {
    id = getInputData().getLong("id", -1);
    nickname = getInputData().getString("nickname");
    zip = getInputData().getInt("zip", -1);
    performAPICalls();
    return Result.success();
}

private void performAPICalls() {

    WeatherApi weatherApi = RetrofitService.createService(WeatherApi.class);


    weatherApi.getWeatherWithZip(zip, Constants.API_KEY).enqueue(new Callback<WeatherResponse>() {
        @Override
        public void onResponse(Call<WeatherResponse> call, Response<WeatherResponse> response) {
            if (response.isSuccessful()) {
                if (response.body() != null) {
                    handleAPIResult(response.body());
                }
            }
        }

        @Override
        public void onFailure(Call<WeatherResponse> call, Throwable t) {
            handleError(t);
        }
    });


}

private void handleAPIResult(WeatherResponse weatherResponse) {
    Log.d(TAG, "handleAPIResult: HERE");
    Completable.fromAction(() -> {
        String timestamp = StringManipulation.getCurrentTimestamp();
        int temperature = Integer.valueOf(Conversions.kelvinToFahrenheit(weatherResponse.getMain().getTemp()));
        String locationName = weatherResponse.getName();
        int windSpeed = Math.round(weatherResponse.getWind().getSpeed());
        int humidity = Math.round(weatherResponse.getMain().getHumidity());

        MyCity city = new MyCity(nickname, zip, timestamp, temperature, locationName, windSpeed, humidity);
        city.setId(id);
        citiesDatabase.myCitiesDao().update(city);
        Log.d(TAG, "run: city added");
    }).observeOn(AndroidSchedulers.mainThread())
            .subscribeOn(Schedulers.io())
            .subscribe();

}

private void handleError(Throwable t) {
    Log.d(TAG, "handleError: here");
}

}

还有道：

  @Dao
public interface MyCitiesDao {

    @Insert
    void insert(MyCity myCity);

    @Query("SELECT * FROM cities ORDER BY id ASC")
    LiveData<List<MyCity>> observeAllCities();

    @Query("SELECT * FROM cities ORDER BY id ASC")
    List<MyCity> getAllCities();

    @Delete
    void delete(MyCity... city);

    @Update
    void update(MyCity... city);
}

Here is what the app looks like

Answer 1

我认为真正的问题是因为你打电话给submitList，因为根据docs

当您调用 submitList 时，它会提交一个新列表以进行比较和显示。

这就是为什么每当您在前一个（已经提交的列表）上调用 submitList 时，它不会计算 Diff 并且不会通知适配器数据集中的更改。

解决方案可能使用以下方法（我认为不是很花哨），但应该可以工作。

submitList(null);
submitList(cities);

另一种解决方案是在您的适配器类中覆盖 submitList

@Override
public void submitList(final List<MyCity> list) {
    super.submitList(list != null ? new ArrayList<>(list) : null);
}

第三种解决方案是创建如下列表的副本

submitList(new ArrayList(cities))

请查看此 stackoverflow 问题以获取更多信息source