使用Retrofit+LiveData时的Error/Loading处理

柔光的暖阳◎ 2023-07-02 11:29 7阅读 0赞

目前还有很多项目使用Retrofit2+LiveData进行API请求，LiveData在不像RxJava那样可以方便地进行Error处理，所以想基于LiveData封装一个工具类，对API请求中的Error/Loading等进行统一处理

## HttpManager ##

open class HttpManager<T>(context: Context, serviceClass: Class<T>) {
    
        private val BASE_URL: String = context.getString(R.string.wallet_api_url)
        private var isLoading: MutableLiveData<Boolean>? = null
        private var error: MutableLiveData<ErrorResponse>? = null
    
        private val service = getRetrofit(
                serviceClass,
                BASE_URL,
                getHttpClient(context)
        )
    
        fun init(
                isLoading: MutableLiveData<Boolean>? = null,
                error: MutableLiveData<ErrorResponse>? = null
        ):T {
            this.isLoading = isLoading
            this.error = error
            return service
        }
    
        private fun createHeader(context: Context, request: Request): Request {
            return request.newBuilder()
                    .addHeader("Accept", "application/json")
                    .build()
        }
    
        private fun getHttpClient(context: Context) : OkHttpClient {
            val interceptor = Interceptor { chain ->
                val response =  chain.proceed(createHeader(context, chain.request()))
                if(response.code() != ErrorCode.HTTP_OK_200.httpErrorCode) {
                    try {
                        val source =  response.body()?.source()
                        source?.request(java.lang.Long.MAX_VALUE)
                        val bodyString = source?.buffer?.clone()?.readString(Charset.forName("UTF-8")).toString()
                        val errorBase = Gson().fromJson(bodyString, ErrorBase::class.java)
                        error?.postValue(ErrorResponse(response.code(), errorBase))
                    } catch (e: Exception) {
                        error?.postValue(ErrorResponse(response.code(), ErrorBase("Unknown Error", null)))
                    }
                }
                response
            }
    
            return OkHttpClient.Builder()
                    .addInterceptor(interceptor)
                    .addInterceptor(getLoggingInterceptor())
                    .eventListener(object: EventListener(){
                        override fun callStart(call: Call) {
                            isLoading?.postValue(true)
                            super.callStart(call)
                        }
    
                        override fun callEnd(call: Call) {
                            isLoading?.postValue(false)
                            super.callEnd(call)
                        }
                    })
                    .readTimeout(5, TimeUnit.SECONDS)
                    .connectTimeout(5, TimeUnit.SECONDS)
                    .build()
        }
    
        private fun getLoggingInterceptor(): HttpLoggingInterceptor {
            val logging = HttpLoggingInterceptor()
            if (BuildConfig.DEBUG) {
                logging.level = HttpLoggingInterceptor.Level.BODY
            } else {
                logging.level = HttpLoggingInterceptor.Level.NONE
            }
            return logging
        }
    
        private fun getRetrofit(serviceClass: Class<T>, baseUrl: String, httpClient: OkHttpClient) : T {
            val retrofit: Retrofit = Retrofit.Builder()
                    .baseUrl(baseUrl)
                    .addConverterFactory(getConverter())
                    .addCallAdapterFactory(RxJava2CallAdapterFactory.create())
                    .client(httpClient)
                    .build()
            return retrofit.create(serviceClass)
        }
    
        private fun getConverter() : Converter.Factory {
            return GsonConverterFactory.create(GsonBuilder()
                    .setFieldNamingPolicy(FieldNamingPolicy.LOWER_CASE_WITH_UNDERSCORES)
                    .create())
        }
    }

HttpManager类中主要完成以下工作：

1.  基于apiService创建Retofit，
2.  通过EventListener处理loading状态
3.  通过Interceptor处理Error

## ExampleApi ##

class ExampleApi(context: Context ) : HttpManager< ExampleApi. ExampleService (
        context, ExampleService::class.java) {
        interface ExampleService {
            @POST("/user/setting")
            fun setting(): Call<ExampleResponse>
        }
    
        fun setting(responseLiveData: MutableLiveData<ExampleResponse>, 
                    isLoading: MutableLiveData<Boolean>?, error: MutableLiveData<ErrorResponse>?) {
            GlobalScope.launch {
                init(isLoading, error)
                        .setting()
                        .enqueue(object: Callback<ExampleResponse> {
                            override fun onFailure(call: Call<ExampleResponse>,
                                                     t: Throwable) {
                                 //error处理由HttpManager负责，故此处 nothing to do
                            }
        
                            override fun onResponse(call: Call<ExampleResponse>,
                                                response: retrofit2.Response<ExampleResponse>) {
                                if (response.isSuccessful) {
                                    responseLiveData.postValue(response.body())
                                }
                            }
                        })
            }
        }
    
        data class ExampleResponse(
                val hoge: Boolean,
                val fuga: String
        )
    }

ExampleApi主要工作：

1.  提供API请求的调用方法， 并接受LiveData参数
2.  继承HttpManager，通过Retrofit进行Api请求

## Activity ##

val response = MutableLiveData<ExampleApi.ExampleResponse>()
    val error = MutableLiveData<ErrorResponse>()
    val isLoading = MutableLiveData<Boolean>()
    
    WalletUserApi(this).setting(response, isLoading, error)
    
    response.observeForever { result ->
        Toast.makeText(this, "response: $result", Toast.LENGTH_SHORT ).show()
    }
    
    error.observeForever { result ->
        Toast.makeText(this, "response: $result", Toast.LENGTH_SHORT ).show()
    }
    
    isLoading.observeForever { 
        //プログレスダイアログ出したりDatabindingでいい感じにする
    }

Activity做的事情比较简单，调用Api类并传入LiveData即可。

LIveData可以放入ViewModel管理，在Activity范围内所有的Fragment或者自定义View等可以方便及时地订阅Api请求过程的最新状态。