croutine_intro

callback.kt

api.fetchUser(object: Callback{
    fun onResponse(userInfo: UserInfo){
        userTextView.text = userInfo.name
    } 
})

callbacks.kt

api.fetchUser(object: Callback{
    fun onResponse(userInfo: UserInfo){
        api.fetchLastOnlineTime(userInfo.userId, object: Callback{
            fun onResponse(userActivity: UserActivity){
                userTextView.text = userInfo.name
                userLastOnlineTime.text = userActivity.time
            }
        })
    }
})

datasource.kt

suspend fun fetchUser(): UserInfo {
    apiService.fetchUser()
}

suspend fun fetchLastOnlineTime(userId: String) : UserActivity {
    apiService.fetchLastOnlineTime(userId)
}

suspend fun fetchData() = withContext(Dispatcher.IO){
    val userInfo = apiService.fetchUser()
    val userActivity = apiService.fetchLastOnlineTime(userId)
    val mappedData = map(userInfo, userActivity)
    mappedData
}

launch.kt

GlobalScope.launch(Dispatchers.Main) {
    val userInfoAndActivity = fetchData()
    statusTextView.text = userInfoAndActivity.lastOnlineTime
}

rx.kt

api.fetchUser()
    .doOnNext(userInfo -> userNameText.text = userInfo.name)
    .flatMap(userInfo -> api.fetchLastOnlineTime(userInfo.userId))
    .doOnNext(userActivity -> userActivity.text = userActivity.name)
    .subscribeOn(Schedulers.io())
    .observeOn(AndroidSchedulers.mainThread())
    .subscribe()

sequential.kt

val userInfo = api.fetchUser()
val userActivity = api.fetchLastOnlineTime(userInfo.userId)
userTextView.text = userInfo.name
userLastOnlineTime.text = userActivity.time