Network Requests with Retrofit in Android

Jun 5 2024 · Kotlin 1.9.22, Android 14, Android Studio Hedgehog | 2023.1.1

Lesson 03: Make a Request With Retrofit

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00:04To start, open MovieDiaryApiService.kt and replace the code inside with the following:

@POST("user/register")
fun registerUser(@Body body: RequestBody): Call<ResponseBody>

@POST("user/login")
fun loginUser(@Body body: RequestBody): Call<ResponseBody>

@GET("user")
fun getProfile(): Call<ResponseBody>

@GET("sampleMovies")
fun getMovies(): Call<ResponseBody>

@POST("movies")
fun postReview(@Body body: RequestBody): Call<ResponseBody>

00:37With the service methods ready, navigate to MovieDiaryApi.kt and delete the old registerUser method. You’ll implement it again to work with Retrofit. To start, add the following code:

fun registerUser(
  username: String,
  email: String,
  password: String,
  onResponse: (String?, Throwable?) -> Unit,
) {}
val jsonBody = JSONObject().apply {
  put("username", username)
  put("email", email)
  put("password", password)
}.toString()
val body = RequestBody.create(MediaType.parse("application/json"), jsonBody)
apiService.registerUser(body).enqueue(object : Callback<ResponseBody> {
  override fun onResponse(call: Call<ResponseBody>, response: Response<ResponseBody>) {

  }

  override fun onFailure(call: Call<ResponseBody>, error: Throwable) {

  }
})
onResponse(null, error)
val message = response.body()?.string()
if (message == null) {
  val error = response.errorBody()?.string()
  onResponse(null, Throwable(error))
  return
} else {
  onResponse(message, null)
}

03:38Implement loginUser in the same way as registerUser. Remove the suspend modifier from the method and update loginUser with the following:

fun loginUser(username: String, password: String, onResponse: (String?, Throwable?) -> Unit) {
  val jsonBody = JSONObject().apply {
    put("username", username)
    put("password", password)
  }.toString()

  val body = RequestBody.create(MediaType.parse("application/json"), jsonBody)

  apiService.loginUser(body).enqueue(object : Callback<ResponseBody> {
    override fun onResponse(call: Call<ResponseBody>, response: Response<ResponseBody>) {
      val message = response.body()?.string()
      if (message == null) {
        val error = response.errorBody()?.string()
        onResponse(null, Throwable(error))
        return
      } else {
        
      }
    }

    override fun onFailure(call: Call<ResponseBody>, error: Throwable) {
      onResponse(null, error)
    }
  })
}
JSONObject(message).run {
  val token = getString("token")
  onResponse(token, null)
}

05:09Navigate back to MovieDiaryApi.kt and scroll down to getMovies. Replace the comment with the following code:

apiService.getMovies().enqueue(object : Callback<ResponseBody> {
  override fun onResponse(call: Call<ResponseBody>, response: Response<ResponseBody>) {

  }

  override fun onFailure(call: Call<ResponseBody>, error: Throwable) {
    onResponse(null, error)
  }
})
if (response.isSuccessful) {
  val movieReviews = mutableListOf<MovieReview>()
  JSONArray(response.body()?.string()).also { array ->
    for (i in 0 until array.length()) {
      array.getJSONObject(i).run {
        MovieReview(
          title = getString("title"),
          description = getString("description"),
          comment = getString("comment")
        ).also { movieReviews.add(it) }
      }
    }
  }
  onResponse(movieReviews, null)
}
else {
  onResponse(null, Throwable(response.errorBody()?.string()))
}
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