将数据从存储库传递到 ViewModel

Question

我需要将速率变量从我的存储库传递到视图模型。 在视图模型中，我有calculateRate方法，单击按钮后我将货币获取到改造问题，然后改造从网络获取数据。在汇率变量中，我有两种货币的兑换，我需要将其传递给视图模型。怎么办？

存储库

public class CurrencyRepository {

private ApiInterface apiInterface;
private  String apiKey = ApiClient.KEY;
private String TAG = "REPOSITORY ";

public CurrencyRepository(Application application) {
   apiInterface = ApiClient.getClient();
}

public LiveData<Currency> getCurrency(String base, final String target, String apiKey) {

    final MutableLiveData<Currency> data = new MutableLiveData<>();
    apiInterface.getCurrentCurrency(base, target, apiKey).enqueue(new Callback<Currency>() {
        @Override
        public void onResponse(Call<Currency> call, Response<Currency> response) {
            data.setValue(response.body());

            String get = data.getValue().getTarget();
            double rate = 0;
            DecimalFormat df = new DecimalFormat("0.00"); //#
            switch (get) {
                case "EUR":
                    rate = data.getValue().getRates().getEUR();
                    break;
                case "PLN":
                    rate = data.getValue().getRates().getPLN();
                    break;
                case "USD":
                    rate = data.getValue().getRates().getUSD();
                    break;
                case "CHF":
                    rate = data.getValue().getRates().getCHF();
                    break;
            }
            Log.d(TAG, String.valueOf(df.format(rate)));
        }

        @Override
        public void onFailure(Call<Currency> call, Throwable t) {

        }
    });
    return data;
}

}

查看模型

public class MainViewModel extends AndroidViewModel {

private CurrencyRepository currencyRepository;
public final ObservableField<String> from = new ObservableField<>();
public final ObservableField<String> to = new ObservableField<>();
public final ObservableFloat value = new ObservableFloat();
public final ObservableField<String> result = new ObservableField<>();


public MainViewModel(Application application) {
   super(application);
   currencyRepository = new CurrencyRepository(application);
}

public void calculateRate() {
    currencyRepository.getCurrency(String.valueOf(from.get()), String.valueOf(to.get()), ApiClient.KEY);
}

}

Answer 1

你可以这样做：

将

rate

定义为

LiveData

字段而不是局部变量：

public class CurrencyRepository {

    private ApiInterface apiInterface;
    private String apiKey = ApiClient.KEY;
    private String TAG = "REPOSITORY ";
    private MutableLiveData<Double> rate = new MutableLiveData(); //or new it in constructor 
    ....

然后在您的服务调用方法中您需要执行以下操作：

public MutableLiveData<Currency> getCurrency(String base, final String target, String apiKey) {

final MutableLiveData<Currency> data = new MutableLiveData<>();
apiInterface.getCurrentCurrency(base, target, apiKey).enqueue(new Callback<Currency>() {
    @Override
    public void onResponse(Call<Currency> call, Response<Currency> response) {
        data.setValue(response.body());

        String get = data.getValue().getTarget();

        DecimalFormat df = new DecimalFormat("0.00"); //#
        switch (get) {
            case "EUR":
                rate.postValue(data.getValue().getRates().getEUR());
                break;
            case "PLN":
                rate.postValue(data.getValue().getRates().getPLN());
                break;
            case "USD":
                rate.postValue(data.getValue().getRates().getUSD());
                break;
            case "CHF":
                rate.postValue(data.getValue().getRates().getCHF());
                break;
        }
        Log.d(TAG, String.valueOf(df.format(rate)));
    }

    @Override
    public void onFailure(Call<Currency> call, Throwable t) {

    }
  });
  return data;
}

在您的存储库中添加

getter

表示速率：

public LiveData<Double> getRate() {
    return rate;
}

在您的

ViewModel

中，您需要一种从存储库获取

rate

的方法：

public class MainViewModel extends ViewModel {
    ...

    public LiveData<Double> getRate(){
         return currencyRepository.getRate();
    }
}

就这样完成了！

您现在可以观察

getRate()

的

View Model

方法，并根据观察者的

onChange()

方法中的值做出反应。

Answer 2

使用 MutableLiveData 并不是将数据从存储库传递到视图模型的好主意，您可以使用回调