android - 使用 Ktor 反序列化 Json 数组的问题

Question

我正在尝试使用 Ktor 和 Kotlinx 序列化从 jsonplaceholder.typicode.com ( here ) 中提取一些虚拟帖子数据并反序列化数组。但是，我收到以下错误:

Error:Expected class kotlinx.serialization.json.JsonObject (Kotlin reflection is not available) as the serialized body of kotlinx.serialization.Polymorphic<List>, but had class kotlinx.serialization.json.JsonArray (Kotlin reflection is not available)

我在代码中的哪个位置指定我期望数据为 JsonObjects 而不是 JsonArrays？这可能是错误，但我没有看到我在代码中指定的位置。

预先感谢您的帮助。

相关代码贴在这里:

LoginRegisterFragment.kt

package com.example.groupupandroid

import android.content.Intent
import android.os.Bundle
import androidx.fragment.app.Fragment
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import androidx.lifecycle.lifecycleScope
import androidx.navigation.Navigation
import androidx.navigation.fragment.findNavController
import com.example.groupupandroid.databinding.ActivityMainBinding
import com.example.groupupandroid.databinding.FragmentLoginRegisterBinding
import data.remote.PostResponse
import data.remote.PostsService
import kotlinx.coroutines.CoroutineScope
import kotlinx.coroutines.GlobalScope
import kotlinx.coroutines.coroutineScope
import kotlinx.coroutines.launch

class LoginRegisterFragment : Fragment(){
    // Getting xml objects
    private var binding: FragmentLoginRegisterBinding? = null
    // Creating service for networking
    private lateinit var service: PostsService

    private var posts: List<PostResponse> = emptyList()

    //@Composable
    override fun onCreateView(
        inflater: LayoutInflater, container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View? {
        binding = FragmentLoginRegisterBinding.inflate(layoutInflater)

        lifecycleScope.launch {getPosts()}

        // Inflate the layout for this fragment
        return binding?.root
    }

    private suspend fun getPosts() {
        service = PostsService.create()
        posts = service.getPosts()
        print(posts)
    }

    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {

        // If register button is tapped make register visible
        binding?.registerToggleButton?.setOnClickListener {
            binding?.registerFields?.visibility = View.VISIBLE
            binding?.loginFields?.visibility = View.GONE
        }

        // If login button is tapped make login visible
        binding?.loginToggleButton?.setOnClickListener {
            binding?.registerFields?.visibility = View.GONE
            binding?.loginFields?.visibility = View.VISIBLE
        }

        // If login button is pushed swap to maps
        binding?.loginButton?.setOnClickListener {
            findNavController().navigate(R.id.loginToHomeScreen)
        }

        // If register button is pushed swap to maps
        binding?.registerButton?.setOnClickListener {
            findNavController().navigate(R.id.loginToHomeScreen)
        }

        binding?.materialButtonToggleGroup?.check(binding?.loginToggleButton!!.id)
    }

    override fun onDestroyView() {
        super.onDestroyView()
        binding = null
    }
}

PostResponse.kt

package data.remote

import kotlinx.serialization.Serializable

@Serializable
data class PostResponse (
    val body: String,
    val title: String,
    val id: Int,
    val userId: Int
)

PostsServiceImplementation.kt

package data.remote

import io.ktor.client.*
import io.ktor.client.call.*
import io.ktor.client.request.*
import io.ktor.client.statement.*
import io.ktor.http.*
import io.ktor.util.*
import java.lang.Exception

class PostsServiceImplementation(private val client: HttpClient): PostsService
 {
    override suspend fun getPosts(): List<PostResponse> {
        return try {
            client.get {url(HttpRoutes.POSTS)}.body()
        } catch(e: Exception){
            println("Error:${e.message}")
            emptyList()
        }
    }

    override suspend fun createPosts(postRequest: PostRequest): PostResponse? {
        return try {
            client.post {
                url(HttpRoutes.POSTS)
                contentType(ContentType.Application.Json)
                setBody(postRequest)
            }.body()
        } catch(e: Exception) {
            println("Error:${e.message}")
            null
        }
    }
}

---

编辑:更多相关代码。

HttpRoutes.kt

package data.remote

object HttpRoutes {

    private const val BASE_URL = "https://jsonplaceholder.typicode.com"

    const val POSTS = "$BASE_URL/posts"
}

PostsService.kt

package data.remote

import io.ktor.client.*
import io.ktor.client.engine.android.*
import io.ktor.client.plugins.contentnegotiation.*
import io.ktor.client.plugins.kotlinx.serializer.*
import io.ktor.client.plugins.logging.*
import io.ktor.client.statement.*
import io.ktor.serialization.kotlinx.json.*

interface PostsService {

    suspend fun getPosts(): List<PostResponse>

    suspend fun createPosts(postRequest: PostRequest): PostResponse?

    companion object {
        fun create():PostsService {
            return PostsServiceImplementation (
                client = HttpClient(Android) {
                    install(Logging) {
                        level = LogLevel.ALL
                    }
                    install(ContentNegotiation) {
                        json()
                    }
                }
            )
        }
    }
}

PostRequest.kt

package data.remote

import kotlinx.serialization.Serializable

@Serializable
data class PostRequest (
    val body: String,
    val title: String,
    val userId: Int
)

Answer 1

我要结束这个问题了。发现我的数据类上显示以下消息:“kotlinx.serialization 编译器插件未应用于该模块，因此不会处理此注释。请确保您已正确设置构建脚本并重新导入项目”。问题是我没有在我的 build.gradle.kts (应用程序)中包含以下行

    kotlin("plugin.serialization") version "1.7.10"

我也使用了 ProGuard，但没有包含对 ProGuard 规则的相关更改(请参阅 here )。