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添加依賴(lài)

implementation 'com.squareup.retrofit2:retrofit:2.11.0'
implementation 'com.squareup.retrofit2:converter-gson:2.11.0'
implementation 'com.squareup.okhttp3:okhttp:4.12.0'

由于需要對(duì) OKHttpClient 做一些操作和定制，這里添加了 okhttp 的依賴(lài)。實(shí)體類(lèi)的轉(zhuǎn)換使用了 gson，為啥用 gson，問(wèn)就是項(xiàng)目里面就是用的 gson，后面再介紹一下其他的converter。

Gson: com.squareup.retrofit2:converter-gson
Jackson: com.squareup.retrofit2:converter-jackson
Moshi: com.squareup.retrofit2:converter-moshi
Protobuf: com.squareup.retrofit2:converter-protobuf
Wire: com.squareup.retrofit2:converter-wire
Simple XML: com.squareup.retrofit2:converter-simplexml
JAXB: com.squareup.retrofit2:converter-jaxb
Scalars (primitives, boxed, and String): com.squareup.retrofit2:converter-scalars

聲明請(qǐng)求接口

interface MainPageApi{
  @GET("app_interface/home_pag/")
  fun getMainPageInfoWithRow():Call<MainPageInfo>
}

創(chuàng)建 Retrofit 對(duì)象

val retrofit = Retrofit.Builder()
    .baseUrl(BASE_URL)
    .addConverterFactory(GsonConverterFactory.create())
    .build()

發(fā)送請(qǐng)求

val mainPageApi = retrofit.create(MainPageApi::class.java)
mainPageApi.getMainPageInfoWithCall().enqueue(object:retrofit2.Callback<MainPageInfo>{
    override fun onResponse(
        call: Call<MainPageInfo>,
        response: retrofit2.Response<MainPageInfo>
    ) {
        Log.e("KotlinActivity","getMainPageInfoWithCall onResponse")
    }

    override fun onFailure(call: Call<MainPageInfo>, t: Throwable) {
        Log.e("KotlinActivity","getMainPageInfoWithCall onFailure")
    }
})

到這里為止，我們還沒(méi)有使用任何協(xié)程相關(guān)的特性，并且沒(méi)有都得寫(xiě)回調(diào)，和 Java 寫(xiě)起來(lái)也沒(méi)啥差別。

支持協(xié)程

我們對(duì)接口的聲明加上suspend修飾

@GET("app_interface/home_pag/")
suspend fun getMainPageInfoWithRow():Call<MainPageInfo>

這時(shí)候上面直接發(fā)送請(qǐng)求的代碼會(huì)報(bào)錯(cuò)： [圖片上傳失敗...(image-ba426c-1714897564066)] 提示我們需要在協(xié)程中調(diào)用，這也簡(jiǎn)單，kotlin 對(duì) activity 有個(gè)擴(kuò)展的lifecycleScope成員變量，稍微修改一下：

lifecycleScope.launch(Dispatchers.IO) {
  mainPageApi.getMainPageInfoWithCall().enqueue(.....)
}

不習(xí)慣這么寫(xiě)的話，可以將網(wǎng)絡(luò)請(qǐng)求寫(xiě)在 ViewModel 中，通過(guò) LiveData創(chuàng)建一個(gè)可觀察對(duì)象實(shí)現(xiàn)數(shù)據(jù)綁定。

不出意外的出意外了，應(yīng)用崩潰，錯(cuò)誤信息

java.lang.IllegalArgumentException: Suspend functions should not return Call, as they already execute asynchronously.
Change its return type to class com.huangyuanlove.androidtest.kotlin.retrofit.MainPageInfo

意思是在協(xié)程中發(fā)起請(qǐng)求已經(jīng)是異步的了，不需要再返回 Call 對(duì)象了，直接返回對(duì)應(yīng)的實(shí)體即可。簡(jiǎn)單，修改一下接口聲明

@GET("app_interface/home_page/")
suspend fun getMainPageInfoWithRow():MainPageInfo

然后修改一下請(qǐng)求

lifecycleScope.launch(Dispatchers.IO) {
  val mainPageInfo = mainPageApi.getMainPageInfo()
  withContext(Dispatchers.Main) {
    refreshUI(mainPageInfo)
  }
}

運(yùn)行一下，一切正常。我們修改一下接口，請(qǐng)求一個(gè)不存在的地址，會(huì)返回404，不出意外，應(yīng)用還是崩潰

retrofit2.HttpException: HTTP 404 
at retrofit2.KotlinExtensions$await$2$2.onResponse(KotlinExtensions.kt:53)
at retrofit2.OkHttpCall$1.onResponse(OkHttpCall.java:164)
at okhttp3.internal.connection.RealCall$AsyncCall.run(RealCall.kt:519)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1167)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:641)
at java.lang.Thread.run(Thread.java:929)
Suppressed: kotlinx.coroutines.internal.DiagnosticCoroutineContextException: [StandaloneCoroutine{Cancelling}@ffa6ad2, Dispatchers.IO]

哦~異常沒(méi)有處理，粗暴點(diǎn)，直接 try-catch，kotlin 中還有runCatching這個(gè)語(yǔ)法糖

val mainPageInfoRow = runCatching { mainPageApi.getMainPageInfoWithRow() }
if (mainPageInfoRow.isFailure) {
    ToastUtils.showToast("請(qǐng)求失敗")
} else if (mainPageInfoRow.isSuccess) {
    ToastUtils.showToast("請(qǐng)求成功")
    withContext(Dispatchers.Main) {
        if (mainPageInfoRow.getOrNull() == null) {
            ToastUtils.showToast("請(qǐng)求結(jié)果為空")
        } else {
            refreshViewWithLaunch(mainPageInfoRow.getOrNull()!!)
        }

    }
}

但是有時(shí)候我們會(huì)用HTTP狀態(tài)碼來(lái)表示一些業(yè)務(wù)上邏輯錯(cuò)誤，并且不同的狀態(tài)碼返回的 JSON 結(jié)構(gòu)還可能不一樣。別問(wèn)為啥要這么搞，應(yīng)該是HTTP 狀態(tài)碼就應(yīng)該表示網(wǎng)絡(luò)請(qǐng)求的狀態(tài)，業(yè)務(wù)狀態(tài)應(yīng)該放在返回的數(shù)據(jù)中約定字段來(lái)處理。問(wèn)就是15年的老代碼，之前就是這么搞的，并且大范圍應(yīng)用，涉及到的部門(mén)、業(yè)務(wù)占半數(shù)以上。這時(shí)候我們需要自定義CallAdapter了

自定義 CallAdapter

這時(shí)候就應(yīng)該翻一下源碼了，在example有個(gè)ErrorHandlingAdapter.java,路徑在samples/src/main/java/com/example/retrofit/ErrorHandlingAdapter.java。我們來(lái)仿寫(xiě)一下，最關(guān)鍵的點(diǎn)在實(shí)現(xiàn)自己的 Call 類(lèi)的時(shí)候，對(duì)callback 的處理。

定義不同的返回狀態(tài)

第一步，創(chuàng)建密閉類(lèi)，來(lái)表示不同的狀態(tài)，這里暫且定義了三種情況

Success:HTTP狀態(tài)碼在[200,300)這個(gè)區(qū)間
NetError:HTTP狀態(tài)碼不在[200,300)這個(gè)區(qū)間
UnknownError:其他錯(cuò)誤

sealed class NetworkResponse<out T : Any, out U : Any> { data class Success(val body: T) : NetworkResponse<T, Nothing>() data class NetError(val httpCode:Int?,val errorMsg:String?,val exception: Throwable?) : NetworkResponse<Nothing, Nothing>() data class UnknownError(val error: Throwable?) : NetworkResponse<Nothing, Nothing>() }

創(chuàng)建自己的Call類(lèi)

這里為了簡(jiǎn)化方便，除了enqueue之外必須重寫(xiě)的方法，都是直接調(diào)用delegate對(duì)應(yīng)的方法

internal class NetworkResponseCall<S : Any, E : Any>(
    private val delegate: Call<S>,
    private val errorConverter: Converter<ResponseBody, E>
) : Call<NetworkResponse<S, E>> {
    override fun clone(): Call<NetworkResponse<S, E>> {
        return NetworkResponseCall(delegate.clone(), errorConverter);
    }

    override fun execute(): Response<NetworkResponse<S, E>> {
        throw UnsupportedOperationException("NetworkResponseCall doesn't support execute")
    }

    override fun isExecuted(): Boolean {
        return delegate.isExecuted;
    }

    override fun cancel() {
        delegate.cancel()
    }

    override fun isCanceled(): Boolean {
        return delegate.isCanceled
    }

    override fun request(): Request {
        return delegate.request()
    }

    override fun timeout(): Timeout {
        return delegate.timeout();
    }
}

下面是關(guān)鍵的enqueue方法,在這里面，將所有的請(qǐng)求都用Response.success返回，不再走Response.error.并且根據(jù)不同的 HTTP 狀態(tài)碼，返回的數(shù)據(jù)等條件轉(zhuǎn)成一開(kāi)始定義的密閉類(lèi)。


override fun enqueue(callback: Callback<NetworkResponse<S, E>>) {
    return delegate.enqueue(object : Callback<S> {
        override fun onResponse(call: Call<S>, response: Response<S>) {
            val body = response.body()
            val code = response.code()
            val error = response.errorBody()

            if (response.isSuccessful) {
                if (body != null) {
                    callback.onResponse(
                        this@NetworkResponseCall,
                        Response.success(NetworkResponse.Success(body))
                    )
                } else {
                    
                    callback.onResponse(
                        this@NetworkResponseCall,
                        Response.success(NetworkResponse.UnknownError(null))
                    )
                }
            } else {
                val errorBody = when {
                    error == null -> null
                    error.contentLength() == 0L -> null
                    else -> NetworkResponse.NetError(code, error.toString(), null)
                }
                if (errorBody != null) {
                    callback.onResponse(
                        this@NetworkResponseCall,
                        Response.success(errorBody)
                    )
                } else {
                    callback.onResponse(
                        this@NetworkResponseCall,
                        Response.success(NetworkResponse.UnknownError(null))
                    )
                }
            }


        }

        override fun onFailure(call: Call<S>, t: Throwable) {
            val networkResponse = when (t) {
                is Exception -> NetworkResponse.NetError(null,null,t)
                else -> NetworkResponse.UnknownError(t)
            }
            callback.onResponse(this@NetworkResponseCall, Response.success(networkResponse))
        }

    })
}

創(chuàng)建 CallAdapter

class NetworkResponseAdapter<S : Any, E : Any>(
    private val successType: Type,
    private val errorBodyConverter: Converter<ResponseBody, E>
) : CallAdapter<S, Call<NetworkResponse<S, E>>> {

    override fun responseType(): Type = successType

    override fun adapt(call: Call<S>): Call<NetworkResponse<S, E>> {
        return NetworkResponseCall(call, errorBodyConverter)
    }
}

創(chuàng)建CallAdapterFactory

class  NetworkResponseAdapterFactory:CallAdapter.Factory(){
    override fun get(
        returnType: Type,
        annotations: Array<out Annotation>,
        retrofit: Retrofit
    ): CallAdapter<*, *>? {
        // suspend functions wrap the response type in `Call`
        if(Call::class.java != getRawType(returnType)){
            return null
        }
        check(returnType is ParameterizedType){
            "return type must be parameterized as Call<NetworkResponse<<Foo>> or Call<NetworkResponse<out Foo>>"
        }
        // get the response type inside the `Call` type
        val responseType = getParameterUpperBound(0,returnType)
        // if the response type is not ApiResponse then we can't handle this type, so we return null
        if(getRawType(responseType) != NetworkResponse::class.java){
            return null
        }


        // the response type is ApiResponse and should be parameterized
        check(responseType is ParameterizedType) { "Response must be parameterized as NetworkResponse<Foo> or NetworkResponse<out Foo>" }

        val successBodyType = getParameterUpperBound(0, responseType)
        val errorBodyType = getParameterUpperBound(1, responseType)

        val errorBodyConverter =
            retrofit.nextResponseBodyConverter<Any>(null, errorBodyType, annotations)

        return NetworkResponseAdapter<Any, Any>(successBodyType, errorBodyConverter)
    }
}

構(gòu)建 Retrofit 實(shí)例時(shí)添加該 Factory

val retrofit = Retrofit.Builder()
    .baseUrl(BASE_URL)
    .addCallAdapterFactory(NetworkResponseAdapterFactory())
    .addConverterFactory(GsonConverterFactory.create())
    .build()

使用typealias簡(jiǎn)化返回類(lèi)型(可選)

data class HttpError(val httpCode:Int,val errorMsg:String?,val exception: Throwable?)
// before
interface DemoApiService {
    suspend fun mainPageInfo(): NetworkResponse<MainPageInfo, HttpError>
}
// after
typealias GenericResponse<S> = NetworkResponse<S, HttpError>

interface ApiService {
    suspend fun mainPageInfo(): GenericResponse<MainPageInfo>
}

使用

在 Activity 中直接使用lifecycleScope啟動(dòng)協(xié)程。

lifecycleScope.launch(Dispatchers.IO) {
    Log.e("KotlinActivity", "lifecycleScope.launch -->>" + Thread.currentThread().name);
    val mainPageInfo = mainPageApi.getMainPageInfo()

    withContext(Dispatchers.Main) {
        Log.e(
            "KotlinActivity",
            "withContext(Dispatchers.Main) -->>" + Thread.currentThread().name
        );
        when(mainPageInfo){

            is NetworkResponse.NetError -> Log.e("KotlinActivity",
                "NetError->$mainPageInfo"
            )
            is NetworkResponse.Success ->  refreshViewWithLaunch(mainPageInfo.body)
            is NetworkResponse.UnknownError -> Log.e("KotlinActivity","UnknownError->" + mainPageInfo.error)
        }
    }
}

或者在 ViewModel 中借助 LiveData 將返回值轉(zhuǎn)化為可觀察對(duì)象

class MainPageInfoViewModel:ViewModel() {
    private val _mainPageInfo  = MutableLiveData<MainPageInfo>()
    val mainPageInfo: LiveData<MainPageInfo> get() = _mainPageInfo
    fun getMainPageInfo(){
        viewModelScope.launch(Dispatchers.IO){
            val result = mainPageApi.getMainPageInfo()
            withContext(Dispatchers.Main){
                when(result){
                    is NetworkResponse.NetError -> Log.e("MainPageInfoViewModel",
                        "NetError->$result"
                    )
                    is NetworkResponse.Success ->  _mainPageInfo.value =  result.body
                    is NetworkResponse.UnknownError -> Log.e("MainPageInfoViewModel","UnknownError->" + result.error)
                }

            }
        }
    }

}

在 Activity 中使用

mainPageInfoModel = ViewModelProvider(this).get(MainPageInfoViewModel::class.java)
mainPageInfoModel.mainPageInfo.observe(this, Observer {
    if (it != null) {
        Log.e("KotlinActivity", "viewmodel獲取結(jié)果成功")
        refreshViewWithViewModelResult(it);
    } else {
        Log.e("KotlinActivity", "viewmodel獲取結(jié)果為空")
    }
})
mainPageInfoModel.getMainPageInfo()

暫時(shí)先這樣吧，基本上夠用了

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在kotlin協(xié)程中使用自定義CallAdapter處理錯(cuò)誤

在kotlin協(xié)程中使用自定義CallAdapter處理錯(cuò)誤

添加依賴(lài)

聲明請(qǐng)求接口

創(chuàng)建 Retrofit 對(duì)象

發(fā)送請(qǐng)求

支持協(xié)程

自定義 CallAdapter

定義不同的返回狀態(tài)

創(chuàng)建自己的Call類(lèi)

創(chuàng)建 CallAdapter

創(chuàng)建CallAdapterFactory

構(gòu)建 Retrofit 實(shí)例時(shí)添加該 Factory

使用typealias簡(jiǎn)化返回類(lèi)型(可選)

使用

推薦閱讀更多精彩內(nèi)容

三个男躁一个女,国精产品一区一手机的秘密,麦子交换系列最经典十句话,欧美 国产 综合 欧美 视频

在kotlin協(xié)程中使用自定義CallAdapter處理錯(cuò)誤

添加依賴(lài)

聲明請(qǐng)求接口

創(chuàng)建 Retrofit 對(duì)象

發(fā)送請(qǐng)求

支持協(xié)程

自定義 CallAdapter

定義不同的返回狀態(tài)

創(chuàng)建自己的Call類(lèi)

創(chuàng)建 CallAdapter

創(chuàng)建CallAdapterFactory

構(gòu)建 Retrofit 實(shí)例時(shí)添加該 Factory

使用typealias簡(jiǎn)化返回類(lèi)型(可選)

使用

推薦閱讀更多精彩內(nèi)容

三个男躁一个女,国精产品一区一手机的秘密,麦子交换系列最经典十句话,欧美国产综合欧美视频