Kotlin 協(xié)程+Retrofit 最優(yōu)雅的網(wǎng)絡請求使用
1.簡介
Retrofit對協(xié)程的支持非常的簡陋。在kotlin中使用不符合kotlin的優(yōu)雅
interface TestServer {
@GET("banner/json")
suspend fun banner(): ApiResponse<List<Banner>>
}
//實現(xiàn)并行捕獲異常的網(wǎng)絡請求
fun oldBanner(){
viewModelScope.launch {
//傳統(tǒng)模式使用retrofit需要try catch
val bannerAsync1 = async {
var result : ApiResponse<List<Banner>>? = null
kotlin.runCatching {
service.banner()
}.onFailure {
Log.e("banner",it.toString())
}.onSuccess {
result = it
}
result
}
val bannerAsync2 = async {
var result : ApiResponse<List<Banner>>? = null
kotlin.runCatching {
service.banner()
}.onFailure {
Log.e("banner",it.toString())
}.onSuccess {
result = it
}
result
}
bannerAsync1.await()
bannerAsync2.await()
}
}
一層嵌套一層键俱，屬實無法忍受峡迷。kotlin應該一行代碼解決問題敞咧，才符合kotlin的優(yōu)雅
使用本框架后
interface TestServer {
@GET("banner/json")
suspend fun awaitBanner(): Await<List<Banner>>
}
//實現(xiàn)并行捕獲異常的網(wǎng)絡請求
fun parallel(){
viewModelScope.launch {
val awaitBanner1 = service.awaitBanner().tryAsync(this)
val awaitBanner2 = service.awaitBanner().tryAsync(this)
//兩個接口一起調(diào)用
awaitBanner1.await()
awaitBanner2.await()
}
}
2.源碼地址
3.查看Retrofit源碼
先看Retrofit create方法
public <T> T create(final Class<T> service) {
validateServiceInterface(service);
return (T)
Proxy.newProxyInstance(
service.getClassLoader(),
new Class<?>[] {service},
new InvocationHandler() {
private final Platform platform = Platform.get();
private final Object[] emptyArgs = new Object[0];
@Override
public @Nullable Object invoke(Object proxy, Method method, @Nullable Object[] args)
throws Throwable {
// If the method is a method from Object then defer to normal invocation.
if (method.getDeclaringClass() == Object.class) {
return method.invoke(this, args);
}
args = args != null ? args : emptyArgs;
return platform.isDefaultMethod(method)
? platform.invokeDefaultMethod(method, service, proxy, args)
: loadServiceMethod(method).invoke(args);//具體調(diào)用
}
});
}
loadServiceMethod(method).invoke(args)進入這個方法看具體調(diào)用
我們查看suspenForResponse中的adapt
@Override
protected Object adapt(Call<ResponseT> call, Object[] args) {
call = callAdapter.adapt(call);//如果用戶不設置callAdapterFactory就使用DefaultCallAdapterFactory
//noinspection unchecked Checked by reflection inside RequestFactory.
Continuation<Response<ResponseT>> continuation =
(Continuation<Response<ResponseT>>) args[args.length - 1];
// See SuspendForBody for explanation about this try/catch.
try {
return KotlinExtensions.awaitResponse(call, continuation);
} catch (Exception e) {
return KotlinExtensions.suspendAndThrow(e, continuation);
}
}
}
后面直接交給協(xié)程去調(diào)用call。具體的okhttp調(diào)用在DefaultCallAdapterFactory障般「苛或者用戶自定義的callAdapterFactory中
因此我們這邊可以自定義CallAdapterFactory在調(diào)用后不進行網(wǎng)絡請求的訪問棘幸，在用戶調(diào)用具體方法時候再進行網(wǎng)絡請求訪問。
4.自定義CallAdapterFactory
Retrofit在調(diào)用后直接進行了網(wǎng)絡請求倦零，因此很不好操作够话。我們把網(wǎng)絡請求的控制權放在我們手里蓝翰，就能隨意操作。
class ApiResultCallAdapterFactory : CallAdapter.Factory() {
override fun get(returnType: Type, annotations: Array<Annotation>, retrofit: Retrofit): CallAdapter<*, *>? {
//檢查returnType是否是Call<T>類型的
if (getRawType(returnType) != Call::class.java) return null
check(returnType is ParameterizedType) { "$returnType must be parameterized. Raw types are not supported" }
//取出Call<T> 里的T女嘲，檢查是否是Await<T>
val apiResultType = getParameterUpperBound(0, returnType)
// 如果不是 Await 則不由本 CallAdapter.Factory 處理 兼容正常模式
if (getRawType(apiResultType) != Await::class.java) return null
check(apiResultType is ParameterizedType) { "$apiResultType must be parameterized. Raw types are not supported" }
//取出Await<T>中的T 也就是API返回數(shù)據(jù)對應的數(shù)據(jù)類型
// val dataType = getParameterUpperBound(0, apiResultType)
return ApiResultCallAdapter<Any>(apiResultType)
}
}
class ApiResultCallAdapter<T>(private val type: Type) : CallAdapter<T, Call<Await<T>>> {
override fun responseType(): Type = type
override fun adapt(call: Call<T>): Call<Await<T>> {
return ApiResultCall(call)
}
}
class ApiResultCall<T>(private val delegate: Call<T>) : Call<Await<T>> {
/**
* 該方法會被Retrofit處理suspend方法的代碼調(diào)用畜份，并傳進來一個callback,如果你回調(diào)了callback.onResponse，那么suspend方法就會成功返回
* 如果你回調(diào)了callback.onFailure那么suspend方法就會拋異常
*
* 所以我們這里的實現(xiàn)是回調(diào)callback.onResponse,將okhttp的call delegate
*/
override fun enqueue(callback: Callback<Await<T>>) {
//將okhttp call放入AwaitImpl直接返回欣尼，不做網(wǎng)絡請求爆雹。在調(diào)用AwaitImpl的await時才真正開始網(wǎng)絡請求
callback.onResponse(this@ApiResultCall, Response.success(delegate.toResponse()))
}
}
internal class AwaitImpl<T>(
private val call : Call<T>,
) : Await<T> {
override suspend fun await(): T {
return try {
call.await()
} catch (t: Throwable) {
throw t
}
}
}
通過上面自定義callAdapter后，我們延遲了網(wǎng)絡請求愕鼓，在調(diào)用Retrofit后并不會請求網(wǎng)絡钙态，只會將網(wǎng)絡請求所需要的call的放入await中。
@GET("banner/json")
suspend fun awaitBanner(): Await<List<Banner>>
我們拿到的Await<List>并沒有做網(wǎng)絡請求菇晃。在這個實體類中包含了okHttp的call册倒。
這時候我們可以定義如下方法就能捕獲異常
suspend fun <T> Await<T>.tryAsync(
scope: CoroutineScope,
onCatch: ((Throwable) -> Unit)? = null,
context: CoroutineContext = SupervisorJob(scope.coroutineContext[Job]),
start: CoroutineStart = CoroutineStart.DEFAULT
): Deferred<T?> = scope.async(context, start) {
try {
await()
} catch (e: Throwable) {
onCatch?.invoke(e)
null
}
}
同樣并行捕獲異常的請求，就可以通過如下方式調(diào)用磺送，優(yōu)雅簡潔了很多
/**
* 并行 async
*/
fun parallel(){
viewModelScope.launch {
val awaitBanner1 = service.awaitBanner().tryAsync(this)
val awaitBanner2 = service.awaitBanner().tryAsync(this)
//兩個接口一起調(diào)用
awaitBanner1.await()
awaitBanner2.await()
}
}
這時候我們發(fā)現(xiàn)網(wǎng)絡請求成功了驻子，解析數(shù)據(jù)失敗。因為我們在數(shù)據(jù)外面套了一層await估灿〕绾牵肯定無法解析成功。
本著哪里錯誤解決哪里的思路馅袁，我們自定義Gson解析
5.自定義Gson解析
class GsonConverterFactory private constructor(private var responseCz : Class<*>,var responseConverter : GsonResponseBodyConverter, private val gson: Gson) : Converter.Factory() {
override fun responseBodyConverter(
type: Type, annotations: Array<Annotation>,
retrofit: Retrofit
): Converter<ResponseBody, *> {
var adapter : TypeAdapter<*>? = null
//檢查是否是Await<T>
if (Utils.getRawType(type) == Await::class.java && type is ParameterizedType){
//取出Await<T>中的T
val awaitType = Utils.getParameterUpperBound(0, type)
if(awaitType != null){
adapter = gson.getAdapter(TypeToken.get(ParameterizedTypeImpl[responseCz,awaitType]))
}
}
//不是awiat正常解析域慷，兼容正常模式
if(adapter == null){
adapter= gson.getAdapter(TypeToken.get(ParameterizedTypeImpl[responseCz,type]))
}
return responseConverter.init(gson, adapter!!)
}
}
class MyGsonResponseBodyConverter : GsonResponseBodyConverter() {
override fun convert(value: ResponseBody): Any {
val jsonReader = gson.newJsonReader(value.charStream())
val data = adapter.read(jsonReader) as ApiResponse<*>
val t = data.data
val listData = t as? ApiPagerResponse<*>
if (listData != null) {
//如果返回值值列表封裝類，且是第一頁并且空數(shù)據(jù) 那么給空異常 讓界面顯示空
if (listData.isRefresh() && listData.isEmpty()) {
throw ParseException(NetConstant.EMPTY_CODE, data.errorMsg)
}
}
// errCode 不等于 SUCCESS_CODE汗销，拋出異常
if (data.errorCode != NetConstant.SUCCESS_CODE) {
throw ParseException(data.errorCode, data.errorMsg)
}
return t!!
}
}
6.本框架使用
添加依賴
maven central 1.1.0
implementation "io.github.cnoke.ktnet:api:?"
寫一個網(wǎng)絡請求數(shù)據(jù)基類
open class ApiResponse<T>(
var data: T? = null,
var errorCode: String = "",
var errorMsg: String = ""
)
實現(xiàn)com.cnoke.net.factory.GsonResponseBodyConverter
class MyGsonResponseBodyConverter : GsonResponseBodyConverter() {
override fun convert(value: ResponseBody): Any {
val jsonReader = gson.newJsonReader(value.charStream())
val data = adapter.read(jsonReader) as ApiResponse<*>
val t = data.data
val listData = t as? ApiPagerResponse<*>
if (listData != null) {
//如果返回值值列表封裝類犹褒，且是第一頁并且空數(shù)據(jù) 那么給空異常 讓界面顯示空
if (listData.isRefresh() && listData.isEmpty()) {
throw ParseException(NetConstant.EMPTY_CODE, data.errorMsg)
}
}
// errCode 不等于 SUCCESS_CODE，拋出異常
if (data.errorCode != NetConstant.SUCCESS_CODE) {
throw ParseException(data.errorCode, data.errorMsg)
}
return t!!
}
}
進行網(wǎng)絡請求
interface TestServer {
@GET("banner/json")
suspend fun awaitBanner(): Await<List<Banner>>
}
val okHttpClient = OkHttpClient.Builder()
.addInterceptor(HeadInterceptor())
.addInterceptor(LogInterceptor())
.build()
val retrofit = Retrofit.Builder()
.client(okHttpClient)
.baseUrl("https://www.wanandroid.com/")
.addCallAdapterFactory(ApiResultCallAdapterFactory())
.addConverterFactory(GsonConverterFactory.create(ApiResponse::class.java,MyGsonResponseBodyConverter()))
.build()
val service: TestServer = retrofit.create(TestServer::class.java)
lifecycleScope.launch {
val banner = service.awaitBanner().await()
}
異步請求同步請求弛针，異常捕獲參考如下try開頭的會捕獲異常化漆，非try開頭不會捕獲。
fun banner(){
lifecycleScope.launch {
//單獨處理異常 tryAwait會處理異常钦奋，如果異常返回空
val awaitBanner = service.awaitBanner().tryAwait()
awaitBanner?.let {
for(banner in it){
Log.e("awaitBanner",banner.title)
}
}
/**
* 不處理異常 異常會直接拋出，統(tǒng)一處理
*/
val awaitBannerError = service.awaitBanner().await()
}
}
/**
* 串行 await
*/
fun serial(){
lifecycleScope.launch {
//先調(diào)用第一個接口await
val awaitBanner1 = service.awaitBanner().await()
//第一個接口完成后調(diào)用第二個接口
val awaitBanner2 = service.awaitBanner().await()
}
}
/**
* 并行 async
*/
fun parallel(){
lifecycleScope.launch {
val awaitBanner1 = service.awaitBanner().async(this)
val awaitBanner2 = service.awaitBanner().async(this)
//兩個接口一起調(diào)用
awaitBanner1.await()
awaitBanner2.await()
}
}
