Android Kotlin Dagger2 provide gson : Parameter specified as non-null is null

Question

i want to provide a single gson instance, so i provide it in my NetworkModule, when i create retrofit api, gson is non null, but when i use gson instance in retrofit class, it is null..

    @Module
    class NetworkModule {

        @Provides
        @Singleton
        fun provideGson(): Gson {
            return Gson()
        }

        @Provides
        @Singleton
        fun provideMyEnterpriseApi(gson: Gson): MyEnterpriseApi {

            //HERE GSON IS NOT NULL

            return RetrofitMyEnterpriseApi(BuildConfig.API_MYENTERPRISE_URL,
                    BuildConfig.API_MYENTERPRISE_CONNECTION_TIMEOUT,


       BuildConfig.API_MYENTERPRISE_READ_TIMEOUT,
                gson)
    }
}

My retrofit api class :

class RetrofitMyEnterpriseApi(baseUrl: String, connectTimeout: Long, readTimeout: Long, private val gson: Gson)
    : RetrofitApi<RetrofitMyEnterpriseCalls>(baseUrl, connectTimeout, readTimeout, RetrofitMyEnterpriseCalls::class.java) {

    override fun buildRetrofit(baseUrl: String, connectTimeout: Long, readTimeout: Long): Retrofit {
        val builder = Retrofit.Builder()

        builder.baseUrl(baseUrl)
        builder.client(buildClient(connectTimeout, readTimeout))
        builder.addCallAdapterFactory(RxJava2CallAdapterFactory.create())
        builder.addConverterFactory(GsonConverterFactory.create(gson))

        return builder.build()
    }

    private fun buildClient(connectTimeout: Long, readTimeout: Long): OkHttpClient {

        //HERE GSON IS NULL

        return OkHttpClient.Builder()
                .addInterceptor(OAuth2Interceptor(gson, this))
                .addInterceptor(LoggingInterceptor.newInstance())
                .connectTimeout(connectTimeout, TimeUnit.MILLISECONDS)
                .readTimeout(readTimeout, TimeUnit.MILLISECONDS)
                .build()
    }
}

RetrofitApi class:

abstract class RetrofitApi<C>
(baseUrl: String, connectTimeout: Long, readTimeout: Long, callsClass: Class<C>) {

    protected val calls: C

    init {
        val retrofit = buildRetrofit(baseUrl, connectTimeout, readTimeout)

        calls = retrofit.create(callsClass)
    }

    protected abstract fun buildRetrofit(baseUrl: String, connectTimeout: Long, readTimeout: Long): Retrofit
}

So, when i provide it's not null, but when i use it in buildClient method is null, i can't see why, i miss something in Kotlin maybe.

Lyofen Lyofen · Accepted Answer · 2017-11-21T09:47:00

I found answer when i posted \o/

So the problem was gson field in RetrofitMyEnterpriseApi class is instancied after the init of RetrofitApi parent class, i think it's strange because i pass it in parameters but..

I just need to call my buildRetrofit method after init of RetrofitMyEnterpriseApi class, or send gson instance to my parent class.

Android Kotlin Dagger2 provide gson : Parameter specified as non-null is null

1 Answers