Have you used the Retrofit library for API interaction in your projects?

Yes, the Retrofit library is widely used in Flutter projects for interacting with REST APIs, especially if the project involves platform-specific code on Android (Java/Kotlin). In pure Flutter (Dart), Retrofit itself is not used directly, but there are similar libraries, such as dio with code generators, inspired by Retrofit.

If we talk about native Android development, Retrofit allows convenient description of HTTP requests via interfaces and annotations, and automatically parses JSON into objects.

Example of Retrofit usage in Android:

interface ApiService {
    @GET("users/{id}")
    suspend fun getUser(@Path("id") id: Int): User
}

val retrofit = Retrofit.Builder()
    .baseUrl("https://api.example.com/")
    .addConverterFactory(GsonConverterFactory.create())
    .build()

val api = retrofit.create(ApiService::class.java)

In Flutter, for API interaction, packages like http or dio are more commonly used.