I'm new in Android Development and I'm trying to fetch json data from DarkSky API, using OkHttp and GSon. Problem is that I need to somehow return response from onResponse method but it's always null.
Here is my code:
class DarkSky : Callback {
private var url: String? = null
private var forecast: Forecast? = null
fun fetchJson(lat: Double, long: Double): Forecast? {
this.url = "${Constants.DARK_SKY_BASE_URL}/${Constants.DARK_SKY_KEY}/$lat,$long?exclude=hourly,flags,offset"
val request = Request.Builder().url(url!!).build()
val client = OkHttpClient()
client.newCall(request).enqueue(this)
return this.forecast // when I debug this its NULL
}
override fun onFailure(call: Call, e: IOException) {
println("error")
}
override fun onResponse(call: Call, response: Response) {
if (response.isSuccessful) {
val body = response.body()?.string()
val gson = GsonBuilder().create()
val forecast = gson.fromJson(body, Forecast::class.java)
parse(forecast)
}
}
private fun parse(response: Forecast) {
this.forecast = response //when I debug this, it contains data I need.
}
}
EDIT:
Made it work with BlockingQueue. But don't know. Is it a good idea?
class DarkSky {
private var url: String? = null
private var forecast: Forecast? = null
fun fetchJson(lat: Double, long: Double): ArrayBlockingQueue<Forecast>? {
this.url = "${Constants.DARK_SKY_BASE_URL}/${Constants.DARK_SKY_KEY}/$lat,$long?exclude=hourly,flags,offset"
val request = Request.Builder().url(url!!).build()
val blockingQueue: ArrayBlockingQueue<Forecast> = ArrayBlockingQueue(1) // <<<
val client = OkHttpClient()
client.newCall(request).enqueue(object : Callback {
override fun onFailure(call: Call, e: IOException) {
println("error")
}
override fun onResponse(call: Call, response: Response) {
if (response.isSuccessful) {
val body = response.body()?.string()
val gson = GsonBuilder().create()
val forecast = gson.fromJson(body, Forecast::class.java)
blockingQueue.add(forecast) // <<<
}
}
})
return blockingQueue
}
}
Don't want to learn bad practices.
That is because
client.newCall(request).enqueue(this)
will execute asynchronously in the background thread. So, by the time you are returning, it doesn't actually have a value assigned.
Solution:
You probably need to pass an object of a class which conforms certain interface and invokes a method of that interface.
Here are changes you need to do
class DarkSky : CallBack {
private var url: String? = null
private var forecast: Forecast? = null
private var onRequestCompleteListener : OnRequestCompleteListener? =null
fun fetchJson(lat: Double, long: Double,callback : OnRequestCompleteListener) {
this.onRequestCompleteListener = callback
this.url = "${Constants.DARK_SKY_BASE_URL}/${Constants.DARK_SKY_KEY}/$lat,$long?exclude=hourly,flags,offset"
val request = Request.Builder().url(url!!).build()
val client = OkHttpClient()
client.newCall(request).enqueue(this)
}
override fun onFailure(call: Call, e: IOException) {
onRequestCompleteListener?.onError()
println("error")
}
override fun onResponse(call: Call, response: Response) {
if (response.isSuccessful) {
val body = response.body()?.string()
val gson = GsonBuilder().create()
val forecast = gson.fromJson(body, Forecast::class.java)
parse(forecast)
}
onRequestCompleteListener?.onSuccess(forecast)
}
private fun parse(response: Forecast) {
this.forecast = response //when I debug this, it contains data I need.
}
}
interface OnRequestCompleteListener{
fun onSuccess(forcast :Forecast)
fun onError()
}