使用 livedata 的 Recyclerview 在數據更改后不更新。 只有在我旋轉屏幕之后

Question

我有一個天氣應用程序，允許用戶保存位置（本地存儲在房間數據庫中）並顯示所述位置的天氣。 當用戶將城市添加到數據庫時，我執行天氣 API 調用，然后將城市添加到數據庫中，並提供所需的信息。

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());
}

}

現在我在用戶界面中有一個按鈕可以一次更新所有城市（最終我希望它是一個簡單的向下滾動來更新或類似的東西）。 問題是，當我單擊更新所有城市時，工作已執行但 recyclerview 未更新（因為新數據未傳遞給它）但如果我更改配置（如旋轉屏幕），新數據將顯示。

這是我的主要課程：

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");
        }
    }
}

更新所有城市工人：

    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");
}

}

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);
}

這是應用程序的樣子

Answer 1

我認為真正的問題是因為根據文檔，您正在調用submitList

當您調用 submitList 時，它會提交一個新列表進行比較和顯示。

這就是為什么每當您在前一個（已提交的列表）上調用 submitList 時，它不會計算 Diff 並且不會通知適配器數據集的更改。

解決方案可能是使用以下方法（在我看來不是很花哨）但應該有效。

submitList(null);
submitList(cities);

另一種解決方案是在您的適配器類中覆蓋 submitList

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

第三種解決方案是創建列表的副本，如下所示

submitList(new ArrayList(cities))

請查看此 stackoverflow 問題以獲取更多信息來源