[Kotlin] Retrofit2 사용해보기

Retrofit?

안드로이드에서 필요한 데이터를 서버와 주고받을 수 있도록 HTTP 통신을 돕는 Third Party Library

📄 build.gradle(Module)

dependencies {
    ...
    
    implementation 'com.squareup.retrofit2:retrofit:2.9.0'
    implementation 'com.squareup.retrofit2:converter-gson:2.9.0'
    implementation 'com.google.code.gson:gson:2.8.6'
}

• Retrofit 라이브러리 추가
  
  
  

📄 AndroidManifest.xml

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.-">

    <uses-permission android:name="android.permission.INTERNET" />
    
    ...
    
</manifest>

• 매니페스트에 인터넷 권한 추가
  
  
  

📄 object ApiClient

object ApiClient {
    private val retrofit = Retrofit.Builder()
        .baseUrl(BASE_URL)
        .addConverterFactory(GsonConverterFactory.create())
        .build()

    val service = retrofit.create(FlatformsService::class.java)
}

• 레트로핏 객체 생성
  
  
  

📄 interface FlatformsService

interface FlatformsService {
    @GET("api/v1/flatforms")
    fun getFlatforms(): Call<FlatformsResponse>
}

📄 JSON 객체와 data class FlatformsResponse

data class FlatformsResponse(
    val code: Int,
    val message: String,
    val data: ArrayList<Flatforms>
)

data class Flatforms(
    val id: Int,
    @SerializedName("title")
    val flatformsName: String
)

//JSON 구조
{
    "code": 200,
    "message": "OK",
    "data": [
        {
            "id": 1,
            "title": "naver"
        },
        {
            "id": 2,
            "title": "daum"
        }
    ]
}

• DTO(Data Transfer Object)
• Json에서 사용된 key의 이름과 안드로이드에서 변수명이 일치하면 @SerializedName 어노테이션을 사용할 필요가 없다
  
  
  
  

📄 MainActivity.kt

class MainActivity : AppCompatActivity() {
    private lateinit var binding: ActivityMainBinding

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        binding = DataBindingUtil.setContentView(this, R.layout.activity_main)

        loadData()
    }

    fun loadData() {
        val service = ApiClient.service

        service.getFlatforms().enqueue(object : Callback<FlatformsResponse> {
            override fun onResponse(
                call: Call<FlatformsResponse>,
                response: Response<FlatformsResponse>
            ) {
                if (response.isSuccessful) {
                   Log.d("isSuccessful", response.body().toString())
                }
            }
        }

            override fun onFailure(call: Call<FlatformsResponse>, t: Throwable) {
                Log.d("onFailure", "$t")
            }
        })
    }
}

📋 패키지 구조

는 이렇게..