暂停协程的执行以等待回调

最近，我将协程应用到我的项目中，看起来一切都很好，但今天遇到了一个问题使用 Coroutine + Retrofit 将文件/图像上传到服务器 https://stackoverflow.com/q/70360995/5856328.

使用协程+Retrofit上传文件似乎没有解决方案，所以必须使用回调进行Retrofit。

//Api interface
interface UploadFileApiKotlin {
    @Multipart
    @POST("/uploadFileApi")
    fun uploadFiles(
        @Part listUri: List<MultipartBody.Part>
    ): Call<Response<List<FileResponse>?>>
}
//ViewModel class
serviceScope.launch {
                //Insert into db
                repository.insertNewExtAct()
                //Send data into server.
                val call = RequestHelper.getUpLoadFilesKotlinRequest().uploadFiles(partList)
                call.enqueue(object : Callback<Response<List<FileResponse>?>> {
                    override fun onResponse(
                        call: Call<Response<List<FileResponse>?>>,
                        response: Response<Response<List<FileResponse>?>>
                    ) {
                        TODO("Not yet implemented")
                    }

                    override fun onFailure(
                        call: Call<Response<List<FileResponse>?>>,
                        t: Throwable
                    ) {
                        TODO("Not yet implemented")
                    }
                })
                //Wait for response from server and do logic
            }

我的问题是：如何暂停协程的执行以等待改造的回调？

您可以使用suspendCoroutine https://kotlinlang.org/api/latest/jvm/stdlib/kotlin.coroutines/suspend-coroutine.html or suspendCancellableCoroutine https://kotlin.github.io/kotlinx.coroutines/kotlinx-coroutines-core/kotlinx.coroutines/suspend-cancellable-coroutine.html使用回调（将回调转换为suspend功能）：

serviceScope.launch {
    //Insert into db
    repository.insertNewExtAct()
    //Send data into server.
    uploadFile()
    //Wait for response from server and do logic
}

suspend fun uploadFile() = suspendCoroutine<Response<List<FileResponse>?>> { continuation ->
    val call = RequestHelper.getUpLoadFilesKotlinRequest().uploadFiles(partList)
    call.enqueue(object : Callback<Response<List<FileResponse>?>> {
        override fun onResponse(
            call: Call<Response<List<FileResponse>?>>,
            response: Response<Response<List<FileResponse>?>>
        ) {
            // Resume coroutine with a value provided by the callback
            continuation.resumeWith(response.data)
        }

        override fun onFailure(
            call: Call<Response<List<FileResponse>?>>,
            t: Throwable
        ) {
            continuation.resumeWithException(t)
        }
    })
}

suspendCoroutine https://kotlinlang.org/api/latest/jvm/stdlib/kotlin.coroutines/suspend-coroutine.html暂停执行它的协程，直到我们决定通过调用适当的方法继续 -Continuation.resume.... suspendCoroutine主要在我们有一些带有回调的遗留代码时使用。

还有suspendCancellableCoroutine https://kotlin.github.io/kotlinx.coroutines/kotlinx-coroutines-core/kotlinx.coroutines/suspend-cancellable-coroutine.html构建器函数，其行为类似于suspendCoroutine具有附加功能 - 提供了一个实现CancellableContinuation到街区。