如何使用android中的可变实时数据将数据存储库的改造响应中继到视图模型？答案

【问题标题】：How to relay retrofit response from data repository to view model using mutable live data in android?如何使用android中的可变实时数据将数据存储库的改造响应中继到视图模型？
【发布时间】：2019-06-13 18:32:36
【问题描述】：

我能够发出网络请求并在我的数据存储库中取回响应，但无法在我的视图模型中获取该响应。

数据存储库：

public class DataRepository {

private APIService apiService;
private static DataRepository INSTANCE = null;

public MutableLiveData<ResponseEntity> loginUser(UserEntity userEntity){

    final MutableLiveData<ResponseEntity> responseEntity = new MutableLiveData<>();
    apiService.loginUser(userEntity)
            .enqueue(new Callback<ResponseEntity>() {
                @Override
                public void onResponse(Call<ResponseEntity> call, Response<ResponseEntity> response) {
                    Log.d(Constants.LOGGER, "from data repository " + response.body());
                    responseEntity.setValue(response.body());
                }

                @Override
                public void onFailure(Call<ResponseEntity> call, Throwable t) {
                    Log.d(Constants.LOGGER, "from data repository: there was an error");
                    responseEntity.setValue(null);
                }
            });
    return responseEntity;
}
}

查看模型：

public class LoginViewModel extends AndroidViewModel {  

private MutableLiveData<ResponseEntity> networkResponse;


public void sendLoginNetworkRequest(UserEntity userEntity){
    networkResponse = mRepository.loginUser(userEntity);
}

public MutableLiveData<ResponseEntity> getResponse(){
    return networkResponse;
}

活动：

public class LoginActivity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    loginViewModel = ViewModelProviders.of(this).get(LoginViewModel.class);
        loginViewModel.getResponse()
            .observe(this, new Observer<ResponseEntity>() {
                @Override
                public void onChanged(@Nullable ResponseEntity responseEntity) {
                    Log.d(Constants.LOGGER, "response entity changed " + responseEntity);
                }
            });
}

    public void loginClicked(View view) {
       loginViewModel.sendLoginNetworkRequest(userEntity);
   }
}

显示来自数据存储库的日志，但没有显示来自活动的日志。我做错了什么？

【问题讨论】：

标签： android retrofit2 android-livedata mutablelivedata

【解决方案1】：

我找到了答案！我必须将我的 DataRepository 类中的 responseEntity MutableLiveData 变量变成一个类变量并创建一个返回该变量的函数，现在它可以工作了！

存储库：

public class DataRepository {

private APIService apiService;
private static DataRepository INSTANCE = null;
final MutableLiveData<ResponseEntity> responseEntity = new MutableLiveData<>();

public void loginUser(UserEntity userEntity){

    apiService.loginUser(userEntity)
            .enqueue(new Callback<ResponseEntity>() {
                @Override
                public void onResponse(Call<ResponseEntity> call, Response<ResponseEntity> response) {
                    Log.d(Constants.LOGGER, "from data repository " + response.body());
                    responseEntity.setValue(response.body());
                }

                @Override
                public void onFailure(Call<ResponseEntity> call, Throwable t) {
                    Log.d(Constants.LOGGER, "from data repository: there was an error");
                    responseEntity.setValue(null);
                }
            });
}
public MutableLiveData<ResponseEntity> getLiveResponses(){
        return responseEntity;
    }
}

视图模型：

public class LoginViewModel extends AndroidViewModel {      

public void sendLoginNetworkRequest(UserEntity userEntity){
    mRepository.loginUser(userEntity);
}

public MutableLiveData<ResponseEntity> getResponse(){
    return mRepository.getLiveResponse;
} 
}

【讨论】：