Gson

Dependencies

implementation("com.google.code.gson:gson:2.8.9")

Data class

data class Music(
    val cover: String,
    val title: String,
    val url: String
) {
    fun title(): String = title.replace(".mp3", "")
}

Fetch API with Gson

object : TypeToken<List<Music>>() {}.type (provided by gson) is for non-generic type

var data by remember { mutableStateOf<List<Music>>(emptyList()) }

withContext(Dispatchers.IO) {
    val jsonString =
    URL("https://skills-music-api.eliaschen.dev/music").openConnection().let {
        BufferedReader(InputStreamReader(it.getInputStream()))
    }.use { it.readText() }
    val gson = Gson()
    val jsonData = object : TypeToken<List<Music>>() {}.type
    data = gson.fromJson(jsonString, jsonData)
}

Display the data

if(data.isNotEmpty()){
    LazyColumn {
        items(data) {
            Text(it.title())
        }
    }
}

Use @SerializedName for custom JSON keys

data class Todo(
    @SerializedName("user_id") val userId: Int,
    @SerializedName("todo_id") val id: Int,
    @SerializedName("task") val title: String,
    @SerializedName("done") val completed: Boolean
)

Local JSON file

Example: data.json located in assets/

{
  "cities": [
    {"name": "Taipei", "population": 2646204},
    {"name": "Kaohsiung", "population": 2773496},
    {"name": "Taichung", "population": 2815100}
  ]
}

Create a dataclass

data class City(val name: String, val population: Int)
data class CityList(val cities: List<City>)

Parsing data into a list

val inputStream = context.assets.open("data.json").BufferReader.use {it.readText()}
val gson = Gson()
gson.fromJson(reader, CityList::class.java)