如何解决与 retrofit2 相关的 NullPointerException。DefaultCallAdapterFactory$ExecutorCallbackCall

问：

我正在尝试制作一个 Pokedex 应用程序，该应用程序使用 retrofit2 从 API 获取口袋妖怪数据。 当我尝试运行它时，它会记录以下错误：

FATAL EXCEPTION: main                                                                                                
Process: com.example.pokemonapp, PID: 10766                                                                                            
java.lang.NullPointerException: Parameter specified as non-null is null: method com.example.pokemonapp.PokeAdapter.<init>, parameter pokes                                                                                      
    at com.example.pokemonapp.PokeAdapter.<init>(Unknown Source:7)                                                                                          
    at com.example.pokemonapp.MainActivity$getPokemon$1.onResponse(MainActivity.kt:31)                                                                                          
    at retrofit2.DefaultCallAdapterFactory$ExecutorCallbackCall$1.lambda$onResponse$0$retrofit2-DefaultCallAdapterFactory$ExecutorCallbackCall$1(DefaultCallAdapterFactory.java:89)                                                                                             
    at retrofit2.DefaultCallAdapterFactory$ExecutorCallbackCall$1$$ExternalSyntheticLambda0.run(Unknown Source:6)                                                                                               
    at android.os.Handler.handleCallback(Handler.java:958)                                                                                                  
    at android.os.Handler.dispatchMessage(Handler.java:99)                                                                                                      
    at android.os.Looper.loopOnce(Looper.java:205)                                                                                                          
    at android.os.Looper.loop(Looper.java:294)                                                                                                              
    at android.app.ActivityThread.main(ActivityThread.java:8177)                                                                                                                    
    at java.lang.reflect.Method.invoke(Native Method)                                                                                                                       
    at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:552)                                                                                                                            
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:971)

MainActivity.kt （英语）

class MainActivity : AppCompatActivity() {
    lateinit var adapter: PokeAdapter
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        getPokemon()
    }

    private fun getPokemon() {
            val pokeball: Call<PokeApiResponse> = PokeInterface.ApiService.pokeInstance.getPokemonList()
            pokeball.enqueue(object: Callback<PokeApiResponse> {
                override fun onResponse(
                    call: Call<PokeApiResponse>,
                    response: Response<PokeApiResponse>
                ) {
                    val pokedex = response.body()
                    if(pokedex!= null)
                    {
                        Log.d("CHECK", pokeball.toString())
                        adapter = PokeAdapter(this@MainActivity, pokedex.pokemons)
                        val pokeList = findViewById<RecyclerView>(R.id.pokemonList)
                        pokeList.adapter = adapter
                        pokeList.layoutManager = LinearLayoutManager(this@MainActivity)
                    }
                }


                override fun onFailure(call: Call<PokeApiResponse>, t: Throwable) {
                    Log.d("CHECK", "Error in fetching Pokemon", t)
                }
            })
        }
    }

ApiService.kt 接口

const val BASE_URL = "https://raw.githubusercontent.com/Biuni/PokemonGO-Pokedex/master/"

interface PokeInterface{
    @GET("pokedex.json")
    fun getPokemonList() : Call<PokeApiResponse>

    //https://raw.githubusercontent.com/Biuni/PokemonGO-Pokedex/master/pokedex.json

    object ApiService{
        val pokeInstance: PokeInterface
        init{
            val retrofit = Retrofit.Builder()
                .baseUrl(BASE_URL)
                .addConverterFactory(GsonConverterFactory.create())
                .build()
            pokeInstance = retrofit.create(PokeInterface::class.java)
        }
    }
}

PokeApiResponse.kt （英语）

data class PokeApiResponse(
    val pokemons: List<Poke>
)

戳.kt

data class Poke(
    val name: String,
    val img: String
)

PokeAdapter.kt （英语）

class PokeAdapter(val context: Context, val pokes: List<Poke>): RecyclerView.Adapter<PokeAdapter.PokemonViewHolder>() {


    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): PokemonViewHolder {
        val view = LayoutInflater.from(context).inflate(R.layout.item_layout, parent, false)
        return PokemonViewHolder(view)
    }

    override fun getItemCount(): Int {
        return pokes.size
    }

    override fun onBindViewHolder(holder: PokemonViewHolder, position: Int) {
        val pokemon = pokes[position]
        holder.pokeTitle.text = pokemon.name
    }

    class PokemonViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {
        var pokeImage = itemView.findViewById<ImageView>(R.id.pokeImage)
        var pokeTitle = itemView.findViewById<TextView>(R.id.pokeName)
    }
}

build.gradle

implementation ("com.squareup.retrofit2:retrofit:2.9.0")
implementation ("com.squareup.retrofit2:converter-gson:2.9.0")

在 MainActivity.kt 中，我尝试记录使用标签“CHECK”获取的数据，它记录了以下消息：

改造2.DefaultCallAdapterFactory$ExecutorCallbackCall@6d104a9

早些时候，当我没有实现时，改造可以正确获取数据，并且获取的数据也正确记录在标签“CHECK”下，但是现在它一直在给出消息。RecyclerViewDefaultCallAdapterFactory$ExecutorCallbackCall

我花了几个小时试图在网上找到解决方案，但没有任何效果。 在这方面的任何帮助将不胜感激。