java - 我无法使用mvvm在两个存储库之间共享变量

Question

我需要在两个存储库之间共享两个变量。我已经尝试了许多不同的解决方案，但是没有一个可行。简而言之:第一个存储库包含用户的最后一个已知位置(地理纬度和经度)，第二个存储库使用指定的端点(例如地理纬度和经度)调用api。事情是我同意接收那些等于0,0的值。您能给我些提示我应该怎么做吗？我观察到的一件事是，整个程序立即运行，而位置存储库需要几秒钟才能真正获得纬度和经度。因此，程序只是不断调用端点等于0,0的api，如上所述。
位置存储库

    public class LocationRepository {

    private double mLatitude, mLongitude;
    
    public void test(Application application) {
        FusedLocationProviderClient client = LocationServices.getFusedLocationProviderClient(application.getApplicationContext());
        {
            if (ContextCompat.checkSelfPermission(
                    application.getApplicationContext(), Manifest.permission.INTERNET) == PackageManager.PERMISSION_GRANTED &&
                    ContextCompat.checkSelfPermission(application.getApplicationContext(), Manifest.permission.ACCESS_FINE_LOCATION) == PackageManager.PERMISSION_GRANTED &&
                    ContextCompat.checkSelfPermission(application.getApplicationContext(), Manifest.permission.ACCESS_COARSE_LOCATION) == PackageManager.PERMISSION_GRANTED) {

                client.getLastLocation().addOnSuccessListener(new OnSuccessListener<Location>() {
                    @Override
                    public void onSuccess(Location location) {
                        mLongitude = location.getLongitude();
                        mLatitude = location.getLatitude();
                    }
                });
            }
        }
    }
}

预测存储库

public MutableLiveData<ForecastModel> testCall() {
MutableLiveData<ForecastModel> data = new MutableLiveData<>();

mApi.test(mLatitude, mLongitude, "metric", API_KEY).enqueue(new Callback<ForecastModel>() {
    @Override
    public void onResponse(Call<ForecastModel> call, Response<ForecastModel> response) {
        if (!response.isSuccessful()) {
            Log.i(TAG, "onResponse: " + response.code());
        }
        data.setValue(response.body());
    }
    @Override
    public void onFailure(Call<ForecastModel> call, Throwable t) {
        Log.i(TAG, "onFailure: " + t.getMessage());
    }
});
return data;
}

ViewModel

private ForecastRepository mForecastRepository;
private LocationRepository mLocationRepository;

private MutableLiveData<ForecastModel> mForecastData;

public ForecastViewModel(@NonNull Application application) {
    super(application);
    mLocationRepository = new LocationRepository();
    mLocationRepository.test(application);

    mForecastRepository = new ForecastRepository();
    mForecastData = mForecastRepository.testCall();
}

Answer 1

您可以在ViewModel和Transformation.switchMap()中使用两个livadata来跟踪更改。每次mLocationData更改时，mForcastData也会更新。如果您不知道switchMap的工作方式，可以检查How and where to use Transformations.switchMap?。
像这样更改您的ViewModel和LocationRepository。
ViewModel

public class ForecastViewModel extends AndroidViewModel {

    private ForcastRepository mForecastRepository;
    private LocationRepostiory mLocationRepository;

    private LiveData<ForecastModel> mForecastData;
    private LiveData<LocationModel> mLocationData;

    public ForecastViewModel(@NonNull Application application) {
        super(application);
        mLocationRepository = new LocationRepostiory();
        mLocationRepository.test(application);
        mLocationData = mLocationRepository.getMutableLiveData();
        mForecastRepository = new ForcastRepository();

        mForecastData = Transformations.switchMap(mLocationData, location->
                mForecastRepository.testCall(location.getLatitude(), location.getLongitude()));
    }

    public LiveData<ForecastModel> getmForecastData() {
        return mForecastData;
    }
}

位置信息库

class LocationRepostiory {

private LocationModel mLocation;
private MutableLiveData<LocationModel> mutableLiveData = new MutableLiveData();

public void test(Application application) {
    FusedLocationProviderClient client = LocationServices.getFusedLocationProviderClient(application.getApplicationContext());
    {
        if (ContextCompat.checkSelfPermission(
                application.getApplicationContext(), Manifest.permission.INTERNET) == PackageManager.PERMISSION_GRANTED &&
                ContextCompat.checkSelfPermission(application.getApplicationContext(), Manifest.permission.ACCESS_FINE_LOCATION) == PackageManager.PERMISSION_GRANTED &&
                ContextCompat.checkSelfPermission(application.getApplicationContext(), Manifest.permission.ACCESS_COARSE_LOCATION) == PackageManager.PERMISSION_GRANTED) {

            client.getLastLocation().addOnSuccessListener(location -> {
                mLocation = new LocationModel(location.getLongitude(),location.getLatitude());
                mutableLiveData.setValue(mLocation);
            });
        }
    }
}

public MutableLiveData<LocationModel> getMutableLiveData() {
    return mutableLiveData;
}
}

预测存储库

public MutableLiveData<ForecastModel> testCall(double mLatitude, double mLongitude ) {
MutableLiveData<ForecastModel> data = new MutableLiveData<>();

mApi.test(mLatitude, mLongitude, "metric", API_KEY).enqueue(new Callback<ForecastModel>() {
    @Override
    public void onResponse(Call<ForecastModel> call, Response<ForecastModel> response) {
        if (!response.isSuccessful()) {
            Log.i(TAG, "onResponse: " + response.code());
        }
        data.setValue(response.body());
    }
    @Override
    public void onFailure(Call<ForecastModel> call, Throwable t) {
        Log.i(TAG, "onFailure: " + t.getMessage());
    }
});
return data;
}

位置模型

class LocationModel {
    private Double longitude, latitude;

    public LocationModel(Double longitude, Double latitude) {
        this.longitude = longitude;
        this.latitude = latitude;
    }

    public Double getLongitude() {
        return longitude;
    }

    public Double getLatitude() {
        return latitude;
    }
}

如果您不想制作额外的LocationModel类，则也可以将位置数据作为List或Arraylist发送。我只喜欢这个。
编辑:有些错误我已纠正。现在代码正在工作。来自ForcastRepository D/TAG中的testCall()方法的Logcat:testCall:90.3993212,23.7793183