通过 mvvm android 进行异常处理

Question

我在 android studio 中使用 MVVM 架构通过改造来访问 Web 服务。在我看来，我已经处理了服务的响应 class。但是我面临的问题是如何处理异常并将它们传递给我的视图class。一种方法是在我的 Bean class 中创建构造函数并将响应和错误都传递给它并更新 UI。但我想要更优化的方式来处理 UI.

中的异常

这是我的存储库代码：

final MutableLiveData<MyBeanClass> myBeanClass = new MutableLiveData<>();
   ApiInterface apiInterface = ApiClient.getClientAuthentication().create(ApiInterface.class);
    Call<MyBeanClass> call = apiInterface.getData(id);
    call.enqueue(new Callback<MyBeanClass>() {
        @Override
        public void onResponse(Call<MyBeanClass> call, Response<MyBeanClass> response) {
            if(response.body()!=null) {
                myBeanClass.setValue(response.body());
            }
        }

        @Override
        public void onFailure(Call<MyBeanClass> call, Throwable t) {
         //How to handle exceptions here and pass the exception to UI without making constructor in bean class
        }
    });

    return myBeanClass;

Answer 1

查看如何从您的存储库代码中完成：

//Take it globally in your repository class, and provide getter for it.
final MutableLiveData<MyBeanClass> myBeanClass = new MutableLiveData<>();
final MutableLiveData<Throwable> error = new MutableLiveData<>();

public void someApiCallMethod() {
    // In your method call for API
    ApiInterface apiInterface = 
    ApiClient.getClientAuthentication().create(ApiInterface.class);
    Call<MyBeanClass> call = apiInterface.getData(id);
    call.enqueue(new Callback<MyBeanClass>() {
        @Override
        public void onResponse(Call<MyBeanClass> call, Response<MyBeanClass> response) {
            if(response.body()!=null) {
                myBeanClass.setValue(response.body());
            }
            // Even you can handle your response error if it's in your response.
        }

        @Override
        public void onFailure(Call<MyBeanClass> call, Throwable t) {
            //Set your error live data from here
            error.setValue(t);
        }
    });
}

从你的 ViewModel Class，创建一个调用你的 repo API 方法的方法，另一个提供你的实时数据以在你的 UI 上观察的方法。

希望对您有所帮助！

Answer 2

而不是创建两个 Mutable 类。您可以只为错误和成功状态甚至加载状态创建一个包装器对象

data class Resource<out T>(val status: Status, val data: T?, val message: String?) {
    companion object {
        fun <T> success(data: T?): Resource<T> {
            return Resource(SUCCESS, data, null)
        }

        fun <T> error(msg: String, data: T?): Resource<T> {
            return Resource(ERROR, data, msg)
        }

        fun <T> loading(data: T?): Resource<T> {
            return Resource(LOADING, data, null)
        }
    }
}

然后使用 MutableLive 数据作为这种类型

final MutableLiveData<Resource<MyBeanClass>> myBeanClass = new MutableLiveData<>();
           ApiInterface apiInterface = ApiClient.getClientAuthentication().create(ApiInterface.class);
            Call<MyBeanClass> call = apiInterface.getData(id);
            call.enqueue(new Callback<MyBeanClass>() {
                @Override
                public void onResponse(Call<MyBeanClass> call, Response<MyBeanClass> response) {
                    if(response.body()!=null) {
                    myBeanClass.setValue(Resource<MyBeanClass>.success(response.body));
                    }
                }

                @Override
                public void onFailure(Call<MyBeanClass> call, Throwable t) {
     myBeanClass.setValue(Resource<MyBeanClass>.error(t.getLocalizedMessage()));
                }
            });

            return myBeanClass;

您可以查看此 google 示例 https://github.com/googlesamples/android-architecture-components/tree/master/GithubBrowserSample

Answer 3

您可以在此处进行交互。从 onFailure 调用接口方法并从 UI 端提供该接口的实现，因此无论何时出错，yiu 都会在您的 UI 端

Answer 4

这里是带有错误处理的 mvvm 的完整实现。首先用 UI 状态和资源创建一个 class。

public class Resource<T> {

    @NonNull public final Status status;
    @Nullable public final T data;
    @Nullable public final String message;

    private Resource(@NonNull Status status, @Nullable T data,
                     @Nullable String message) {
        this.status = status;
        this.data = data;
        this.message = message;
    }

    public static <T> Resource<T> success(@NonNull T data) {
        return new Resource<>(Status.SUCCESS, data, null);
    }

    public static <T> Resource<T> error(String msg, @Nullable T data) {
        return new Resource<>(Status.ERROR, data, msg);
    }

    public static <T> Resource<T> loading(@Nullable T data) {
        return new Resource<>(Status.LOADING, data, null);
    }


    public enum Status { SUCCESS, ERROR, LOADING }
}

在你的存储库上class做

public LiveData<Resource<MyBeanClass>> getDetail(String movieId) {
        final MutableLiveData<Resource<MyBeanClass>> myBeanClass = new MutableLiveData<>();
        ApiInterface apiInterface = new ApiClient().getClient().create(ApiInterface.class);

   Call<MyBeanClass> call = apiInterface.getData(id);
        call.enqueue(new Callback<MyBeanClass>() {

            @Override
            public void onResponse(Call<MyBeanClass> call, Response<MyBeanClass> response) {
                if (response.body() != null) {
                    MyBeanClass body = response.body();
                    myBeanClass.setValue(Resource.success(body));
                }
            }

            @Override
            public void onFailure(Call<MyBeanClass> call, Throwable t) {
                myBeanClass.setValue(Resource.error(t.getMessage(),null));
            }
        });

        return myBeanClass;
    }

在你的 viewModel 上 class

public class MyViewModel extends ViewModel {

    private LiveData<Resource<MyBeanClass>> myLiveData;

    public void init(String id) {
        movieLiveData = new MyRepository().getInstance().getDetail(id);

    }

    
    public LiveData<Resource<MyBeanClass>> getMyLiveData() {
        return myLiveData;
    }
}

还有你的 Activity class

final MyViewModel viewModel =
                ViewModelProviders.of(this).get(MyViewModel.class);
        viewModel.init(id);
        viewModel.getMyLiveData().observe(this, finalData -> {

            switch (finalData.status) {
                case SUCCESS:
                    loadDetail(finalData.data);
                    break;
                case LOADING:
                    break;
                case ERROR:
                    Toast.makeText(this, "no Internet", Toast.LENGTH_SHORT).show();
                    break;
            }

        });

如果有帮助，别忘了投票哦。快乐编码

Answer 5

public MutableLiveData<String> responseMessage = new MutableLiveData<>();
public MutableLiveData<String> errorMessage = new MutableLiveData<>();                                           ApiInterface apiInterface = ApiClient.getClientAuthentication().create(ApiInterface.class);
Call<MyBeanClass> call = apiInterface.getData(id);
call.enqueue(new Callback<MyBeanClass>() {
    @Override
    public void onResponse(Call<MyBeanClass> call, Response<MyBeanClass> response) {
        if(response.body()==null) {
          //pick server error message
          JSONObject jObjError = new JSONObject(response.errorBody().string());
          Log.d("Error",jObjError.getString("message"))
        }else{
        myBeanClass.setValue(Resource<MyBeanClass>.success(response.body));
        }
    }

    @Override
    public void onFailure(Call<MyBeanClass> call, Throwable t) {
     Log.d("Error", t.getMessage());
     errorMessage.setValue(t.getMessage());
    }
});

只需使用两个 MutableLiveData，一个用于成功响应，另一个用于错误响应，并根据这些响应更新您的 UI。

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