android - 改造 2.6.0 异常 : java. lang.IllegalArgumentException : Unable to create call adapter for kotlinx. coroutines.Deferred

Question

我有一个使用 Kotlin 协程和 Retrofit 的项目。

我有这些依赖项:

implementation 'com.squareup.retrofit2:retrofit:2.5.0'
implementation 'com.squareup.retrofit2:converter-gson:2.5.0'
implementation 'com.jakewharton.retrofit:retrofit2-kotlin-coroutines-adapter:0.9.2'

今天我把项目中的Retrofit更新到了2.6.0。在 https://github.com/JakeWharton/retrofit2-kotlin-coroutines-adapter据记载，它现在已被弃用。在 https://github.com/square/retrofit/blob/master/CHANGELOG.md#version-260-2019-06-05据记载，Retrofit 目前支持suspend。

因此，我删除了 retrofit2-kotlin-coroutines-adapter:0.9.2 并在 Retrofit 客户端中更改了这些行:

        retrofit = Retrofit.Builder()
            .baseUrl(SERVER_URL)
            .client(okHttpClient)
            .addConverterFactory(MyGsonFactory.create(gson))
            //.addCallAdapterFactory(CoroutineCallAdapterFactory()) - removed it.
            .build()

运行时，第一个请求捕获异常:

java.lang.IllegalArgumentException: Unable to create call adapter for kotlinx.coroutines.Deferred<com.package.model.response.UserInfoResponse>
    for method Api.getUserInfo

据我所知，我可以使用 CallAdapter.Factory() 而不是 CoroutineCallAdapterFactory()，但它是抽象的。

如果在 Api 类中，我更改了一个在开头添加 suspend 的请求:

@FormUrlEncoded
@POST("user/info/")
suspend fun getUserInfo(@Field("token") token: String): Deferred<UserInfoResponse>

override suspend fun getUserInfo(token: String): Deferred<UserInfoResponse> =
    service.getUserInfo(token)

我得到这个异常:

java.lang.RuntimeException: Unable to invoke no-args constructor for kotlinx.coroutines.Deferred<com.package.model.response.UserInfoResponse>. Registering an InstanceCreator with Gson for this type may fix this problem.

Answer 1

阅读 https://github.com/square/retrofit/blob/master/CHANGELOG.md#version-260-2019-06-05我看到了:

New: Support suspend modifier on functions for Kotlin! This allows you to express the asynchrony of HTTP requests in an idiomatic fashion for the language.

@GET("users/{id}") suspend fun user(@Path("id") long id): User

Behind the scenes this behaves as if defined as fun user(...): Call and then invoked with Call.enqueue. You can also return Response for access to the response metadata.

Currently this integration only supports non-null response body types. Follow issue 3075 for nullable type support.

我这样更改了请求:添加了 suspend 并删除了 Deferred:

@FormUrlEncoded
@POST("user/info/")
suspend fun getUserInfo(@Field("token") token: String): UserInfoResponse


override suspend fun getUserInfo(token: String): UserInfoResponse =
    service.getUserInfo(token)

然后在交互器中(或者只是在调用方法 getUserInfo(token) 时)移除 await():

override suspend fun getUserInfo(token: String): UserInfoResponse =
    // api.getUserInfo(token).await() - was before.
    api.getUserInfo(token)

更新

有一次我遇到下载PDF文件需要去掉Api类中的suspend的情况。参见 How to download PDF file with Retrofit and Kotlin coroutines? .