I followed everything carefully, step by step, but I can't find what the problem is.
Whenever I fill in the name of the movie I intend to search by, the app crashes and it says this:
java.lang.NullPointerException: response.body() must not be null
Does anyone have any idea? Here is the following code.
MovieList.kt
class MovieList {
val imdbID: String
val Title: String
val Year: String
val Plot: String
val Poster: String
constructor(imdbID: String, Title: String, Year: String, Plot: String, Poster: String) {
this.imdbID = imdbID
this.Title = Title
this.Year = Year
this.Plot = Plot
this.Poster = Poster
}
}
OMDbApi.kt
interface OMDbApi {
#GET("t={Title}")
fun getMovieByTitle(#Path("Title") Title: String): Call<MovieList>
}
OMDbApiClient.kt
class OMDbApiClient {
companion object{
private var omdbapi: OMDbApi? = null
fun getOMDbApi(): OMDbApi?{
if(omdbapi == null){
omdbapi = Retrofit.Builder()
.baseUrl("http://www.omdbapi.com/?&apikey=eb73867f")
.addConverterFactory(GsonConverterFactory.create())
.build()
.create(OMDbApi::class.java);
}
return omdbapi
}
}
}
FirstFragment.kt
class FirstFragment : Fragment() {
private lateinit var omdbapiClient: OMDbApi
private lateinit var tvMovieTitle: TextView
private lateinit var ivImagePoster: ImageView
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
return inflater.inflate(R.layout.fragment_first, container, false)
}
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
omdbapiClient = OMDbApiClient.getOMDbApi()!!
val movieId: EditText = view.findViewById<EditText>(R.id.TitleId)
tvMovieTitle = view.findViewById(R.id.MovieTitleId)
ivImagePoster = view.findViewById(R.id.MoviePosterId)
movieId.setOnEditorActionListener { v, actionId, event ->
if(actionId == EditorInfo.IME_ACTION_DONE || actionId == EditorInfo.IME_ACTION_NEXT){
val movietitle: String = movieId.text.toString()
searchMovieByTitle(movietitle)
true
}
else{
Toast.makeText(activity, "Error!", Toast.LENGTH_LONG).show()
false
}
}
}
private fun searchMovieByTitle(movietitle: String) {
omdbapiClient.getMovieByTitle(movietitle).enqueue(object : Callback<MovieList>{
override fun onResponse(call: Call<MovieList>?, response: Response<MovieList>) {
displayData(response.body())
Toast.makeText(activity, "Success!", Toast.LENGTH_LONG).show()
}
override fun onFailure(call: Call<MovieList>?, t: Throwable?) {
Toast.makeText(activity, "Error!", Toast.LENGTH_LONG).show()
}
})
}
private fun displayData(data: MovieList) {
tvMovieTitle.text = data.Title
Glide.with(this).load(data.Poster).into(ivImagePoster)
}
}
I think you are getting an error response and that's why the response.body() is null. You should be handling an error response gracefully, instead of expecting the body to always not be null, but that is another matter.
I think the following lines of code are at fault:
interface OMDbApi {
#GET("t={Title}")
fun getMovieByTitle(#Path("Title") Title: String): Call<MovieList>
}
The 'Title' should be a #Query parameter instead of a #Path parameter, because the &t= part in the API url is a query parameter. When it is a query parameter you also don't specify it as part of the path in #GET.
Your code would then become:
interface OMDbApi {
#GET("")
fun getMovieByTitle(#Query("t") title: String): Call<MovieList>
}
Do this change and see if you still get an error response. You might want to check the log in the 'Logcat' tab to see what error you are getting back from the API.
For that you might have to enable a higher logging level. This is done by adding a logging interceptor when building the Retrofit client.
// Build a http client with logging enabled
val client = OkHttpClient.Builder()
.addInterceptor(HttpLoggingInterceptor().apply {
// you can also use Level.BODY for even more log information
level = HttpLoggingInterceptor.Level.BASIC
})
.build()
omdbapi = Retrofit.Builder()
.client(client) // add this line to use your http client
.baseUrl("http://www.omdbapi.com/?&apikey=eb73867f")
.addConverterFactory(GsonConverterFactory.create())
.build()
.create(OMDbApi::class.java);
The following code solved my problem.
interface OMDbApi {
#GET("?apikey=[your api key]&")
fun getMovieByTitle(#Query("t") Title: String): Call<MovieList>
}
Related
The question about post requests in android has been asked before, but all the solutions I've tried have not worked properly. On top of that, a lot of them seem to be overly complicated as well. All I wish to do is make a post to a specific sight with a few body parameters. Is there any simple way to do that?
Let me explain my request calling structure using Retrofit.
build.gradle(app)
// Retrofit + GSON
implementation 'com.squareup.okhttp3:logging-interceptor:4.4.0'
implementation "com.squareup.retrofit2:retrofit:2.9.0"
implementation "com.squareup.retrofit2:converter-gson:2.9.0"
ApiClient.kt
object ApiClient {
private const val baseUrl = ApiInterface.BASE_URL
private var retrofit: Retrofit? = null
private val dispatcher = Dispatcher()
fun getClient(): Retrofit? {
val logging = HttpLoggingInterceptor()
if (BuildConfig.DEBUG)
logging.level = HttpLoggingInterceptor.Level.BODY
else
logging.level = HttpLoggingInterceptor.Level.NONE
if (retrofit == null) {
retrofit = Retrofit.Builder()
.client(OkHttpClient().newBuilder().readTimeout(120, TimeUnit.SECONDS)
.connectTimeout(120, TimeUnit.SECONDS).retryOnConnectionFailure(false)
.dispatcher(
dispatcher
).addInterceptor(Interceptor { chain: Interceptor.Chain? ->
val newRequest = chain?.request()!!.newBuilder()
return#Interceptor chain.proceed(newRequest.build())
}).addInterceptor(logging).build()
)
.baseUrl(baseUrl)
.addConverterFactory(GsonConverterFactory.create())
.build()
}
return retrofit
}
}
ApiClient will be used to initialize Retrofit singleton object, also initialize logging interceptors so you can keep track of the requests and responses in the logcat by using the keyword 'okhttp'.
SingleEnqueueCall.kt
object SingleEnqueueCall {
var retryCount = 0
lateinit var snackbar: Snackbar
fun <T> callRetrofit(
activity: Activity,
call: Call<T>,
apiName: String,
isLoaderShown: Boolean,
apiListener: IGenericCallBack
) {
snackbar = Snackbar.make(
activity.findViewById(android.R.id.content),
Constants.CONST_NO_INTERNET_CONNECTION, Snackbar.LENGTH_INDEFINITE
)
if (isLoaderShown)
activity.showAppLoader()
snackbar.dismiss()
call.enqueue(object : Callback<T> {
override fun onResponse(call: Call<T>, response: Response<T>) {
hideAppLoader()
if (response.isSuccessful) {
retryCount = 0
apiListener.success(apiName, response.body())
} else {
when {
response.errorBody() != null -> try {
val json = JSONObject(response.errorBody()!!.string())
Log.e("TEGD", "JSON==> " + response.errorBody())
Log.e("TEGD", "Response Code==> " + response.code())
val error = json.get("message") as String
apiListener.failure(apiName, error)
} catch (e: Exception) {
e.printStackTrace()
Log.e("TGED", "JSON==> " + e.message)
Log.e("TGED", "Response Code==> " + response.code())
apiListener.failure(apiName, Constants.CONST_SERVER_NOT_RESPONDING)
}
else -> {
apiListener.failure(apiName, Constants.CONST_SERVER_NOT_RESPONDING)
return
}
}
}
}
override fun onFailure(call: Call<T>, t: Throwable) {
hideAppLoader()
val callBack = this
if (t.message != "Canceled") {
Log.e("TGED", "Fail==> " + t.localizedMessage)
if (t is UnknownHostException || t is IOException) {
snackbar.setAction("Retry") {
snackbar.dismiss()
enqueueWithRetry(activity, call, callBack, isLoaderShown)
}
snackbar.show()
apiListener.failure(apiName, Constants.CONST_NO_INTERNET_CONNECTION)
} else {
retryCount = 0
apiListener.failure(apiName, t.toString())
}
} else {
retryCount = 0
}
}
})
}
fun <T> enqueueWithRetry(
activity: Activity,
call: Call<T>,
callback: Callback<T>,
isLoaderShown: Boolean
) {
activity.showAppLoader()
call.clone().enqueue(callback)
}
}
SingleEnqueueCall will be used for calling the retrofit, it is quite versatile, written with onFailure() functions and by passing Call to it, we can call an API along with ApiName parameter so this function can be used for any possible calls and by ApiName, we can distinguish in the response that which API the result came from.
Constants.kt
object Constants {
const val CONST_NO_INTERNET_CONNECTION = "Please check your internet
connection"
const val CONST_SERVER_NOT_RESPONDING = "Server not responding!
Please try again later"
const val USER_REGISTER = "/api/User/register"
}
ApiInterface.kt
interface ApiInterface {
companion object {
const val BASE_URL = "URL_LINK"
}
#POST(Constants.USER_REGISTER)
fun userRegister(#Body userRegisterRequest: UserRegisterRequest):
Call<UserRegisterResponse>
}
UserRegisterRequest.kt
data class UserRegisterRequest(
val Email: String,
val Password: String
)
UserRegisterResponse.kt
data class UserRegisterResponse(
val Message: String,
val Code: Int
)
IGenericCallBack.kt
interface IGenericCallBack {
fun success(apiName: String, response: Any?)
fun failure(apiName: String, message: String?)
}
MyApplication.kt
class MyApplication : Application() {
companion object {
lateinit var apiService: ApiInterface
}
override fun onCreate() {
super.onCreate()
apiService = ApiClient.getClient()!!.create(ApiInterface::class.java)
}
}
MyApplication is the application class to initialize Retrofit at the launch of the app.
AndroidManifest.xml
android:name=".MyApplication"
You have to write above tag in AndroidManifest inside Application tag.
MainActivity.kt
class MainActivity : AppCompatActivity(), IGenericCallBack {
private lateinit var binding: ActivityMainBinding
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
binding = ActivityMainBinding.inflate(layoutInflater)
setContentView(binding.root)
val call = MyApplication.apiService.userRegister(UserRegisterRequest(email, password))
SingleEnqueueCall.callRetrofit(this, call, Constants.USER_REGISTER, true, this)
}
override fun success(apiName: String, response: Any?) {
val model = response as UserRegisterResponse
}
override fun failure(apiName: String, message: String?) {
if (message != null) {
showToastMessage(message)
}
}
}
Firstly, we create a call object by using the API defined in ApiInterface and passing the parameters (if any). Then using SingleEnqueueCall, we pass the call to the retrofit along with ApiName and the interface listener IGenericCallBack by using this. Remember to implement it to respective activity or fragment as above.
Secondly, you will have the response of the API whether in success() or failure() function overriden by IGenericCallBack
P.S: You can differentiate which API got the response by using the ApiName parameter inside success() function.
override fun success(apiName: String, response: Any?) {
when(ApiName) {
Constants.USER_REGISTER -> {
val model = response as UserRegisterResponse
}
}
}
The whole concept is to focus on reusability, now every API call has to create a call variable by using the API's inside ApiInterface then call that API by SingleEnqueueCall and get the response inside success() or failure() functions.
I want to use coroutines in my project only when I use coroutines I get the error :Unable to invoke no-args constructor. I don't know why it's given this error. I am also new to coroutines.
here is my apiclient class:
class ApiClient {
val retro = Retrofit.Builder()
.baseUrl(Constants.BASE_URL)
.addConverterFactory(GsonConverterFactory.create())
.build()
}
Here is my endpoint class:
#GET("v2/venues/search")
suspend fun get(
#Query("near") city: String,
#Query("limit") limit: String = Constants.limit,
#Query("radius") radius: String = Constants.radius,
#Query("client_id") id: String = Constants.clientId,
#Query("client_secret") secret: String = Constants.clientSecret,
#Query("v") date: String
): Call<VenuesMainResponse>
my Repository class:
class VenuesRepository() {
private val _data: MutableLiveData<VenuesMainResponse?> = MutableLiveData(null)
val data: LiveData<VenuesMainResponse?> get() = _data
suspend fun fetch(city: String, date: String) {
val retrofit = ApiClient()
val api = retrofit.retro.create(VenuesEndpoint::class.java)
api.get(
city = city,
date = date
).enqueue(object : Callback<VenuesMainResponse>{
override fun onResponse(call: Call<VenuesMainResponse>, response: Response<VenuesMainResponse>) {
val res = response.body()
if (response.code() == 200 && res != null) {
_data.value = res
} else {
_data.value = null
}
}
override fun onFailure(call: Call<VenuesMainResponse>, t: Throwable) {
_data.value = null
}
})
}
}
my ViewModel class:
class VenueViewModel( ) : ViewModel() {
private val repository = VenuesRepository()
fun getData(city: String, date: String): LiveData<VenuesMainResponse?> {
viewModelScope.launch {
try {
repository.fetch(city, date)
} catch (e: Exception) {
Log.d("Hallo", "Exception: " + e.message)
}
}
return repository.data
}
}
part of activity class:
class MainActivity : AppCompatActivity(){
private lateinit var venuesViewModel: VenueViewModel
private lateinit var adapter: HomeAdapter
private var searchData: List<Venue>? = null
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
val editText = findViewById<EditText>(R.id.main_search)
venuesViewModel = ViewModelProvider(this)[VenueViewModel::class.java]
venuesViewModel.getData(
city = "",
date = ""
).observe(this, Observer {
it?.let { res ->
initAdapter()
rv_home.visibility = View.VISIBLE
adapter.setData(it.response.venues)
searchData = it.response.venues
println(it.response.venues)
}
})
this is my VenuesMainResponse data class
data class VenuesMainResponse(
val response: VenuesResponse
)
I think the no-args constructor warning should be related to your VenuesMainResponse, is it a data class? You should add the code for it as well and the complete Log details
Also, with Coroutines you should the change return value of the get() from Call<VenuesMainResponse> to VenuesMainResponse. You can then use a try-catch block to get the value instead of using enqueue on the Call.
Check this answer for knowing about it and feel free to ask if this doesn't solve the issue yet :)
UPDATE
Ok so I just noticed that it seems that you are trying to use the foursquare API. I recently helped out someone on StackOverFlow with the foursquare API so I kinda recognize those Query parameters and the Venue response in the code you provided above.
I guided the person on how to fetch the Venues from the Response using the MVVM architecture as well. You can find the complete code for getting the response after the UPDATE block in the answer here.
This answer by me has code with detailed explanation for ViewModel, Repository, MainActivity, and all the Model classes that you will need for fetching Venues from the foursquare API.
Let me know if you are unable to understand it, I'll help you out! :)
RE: UPDATE
So here is the change that will allow you to use this code with Coroutines as well.
Repository.kt
class Repository {
private val _data: MutableLiveData<mainResponse?> = MutableLiveData(null)
val data: LiveData<mainResponse?> get() = _data
suspend fun fetch(longlat: String, date: String) {
val retrofit = Retro()
val api = retrofit.retro.create(api::class.java)
try {
val response = api.get(
longLat = longlat,
date = date
)
_data.value = response
} catch (e: Exception) {
_data.value = null
}
}
}
ViewModel.kt
class ViewModel : ViewModel() {
private val repository = Repository()
val data: LiveData<mainResponse?> = repository.data
fun getData(longLat: String, date: String) {
viewModelScope.launch {
repository.fetch(longLat, date)
}
}
}
api.kt
interface api {
#GET("v2/venues/search")
suspend fun get(
#Query("ll") longLat: String,
#Query("client_id") id: String = Const.clientId,
#Query("client_secret") secret: String = Const.clientSecret,
#Query("v") date: String
): mainResponse
}
MainActivity.kt
private val viewModel by viewModels<ViewModel>()
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
viewModel.getData(
longLat = "40.7,-74",
date = "20210718" // date format is: YYYYMMDD
)
viewModel.data
.observe(this, Observer {
it?.let { res ->
res.response.venues.forEach { venue ->
val name = venue.name
Log.d("name ",name)
}
}
})
}
}
I try to recover the data of a player with the league of legends API however the response to my request is always null and those without an error message in my logcat.
here is my retrofit call:
public interface LolApiService {
#GET("summoners/by-name/")
Call<SummonerData> getSummonerData (#Query("summonerName")String summonerName, #Query("key") String key);
}
here is my repository:
class LolApiRepository(val application: Application) {
val response = MutableLiveData<SummonerData>()
fun getSummonerID(summonerName: String, key: String): MutableLiveData<SummonerData> {
// val responseData = MutableLiveData<SummonerData>()
val retrofit = Retrofit.Builder()
.baseUrl("https://euw1.api.riotgames.com/lol/summoner/v4/")
.addConverterFactory(GsonConverterFactory.create())
.build()
val service = retrofit.create(LolApiService::class.java)
service.getSummonerData(summonerName, key).enqueue(object : Callback<SummonerData> {
override fun onFailure(call: Call<SummonerData>, t: Throwable) {
Toast.makeText(application, "Error wile accessing the API", Toast.LENGTH_SHORT)
.show()
}
override fun onResponse(call: Call<SummonerData>, resp: Response<SummonerData>) {
Log.d("LolApiRepository", "LolApiRepository:" + resp.body().toString())
if (resp.body() != null) {
Toast.makeText(application, "Success accessing the API", Toast.LENGTH_SHORT)
.show()
response.value = (resp.body() as SummonerData)
} else {
Log.d("LolApiRepository", "LolApiRepository:" + resp.errorBody().toString())
Toast.makeText(application, "Error wile accessing the API", Toast.LENGTH_SHORT)
.show()
}
}
})
return response
}
}
my data model in which I retrieve the result of my query:
class SummonerData {
#SerializedName("id")
#Expose
var id: String? = null
#SerializedName("accountId")
#Expose
var accountId: String? = null
#SerializedName("puuid")
#Expose
var puuid: String? = null
#SerializedName("name")
#Expose
var name: String? = null
#SerializedName("profileIconId")
#Expose
var profileIconId: Int? = null
#SerializedName("revisionDate")
#Expose
var revisionDate: Int? = null
#SerializedName("summonerLevel")
#Expose
var summonerLevel: Int? = null
}
the fragment in which I want to display the data:
class LolStatFragment : Fragment() {
private lateinit var mViewModel: LolApiViewModel
private val apiKey = "api_key=RGAPI-bb27988b-cbb1-4767-b18b-icar8e90c308"
override fun onCreateView(
inflater: LayoutInflater,
container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
val view = inflater.inflate(R.layout.fragment_lol_stat, container, false)
mViewModel = ViewModelProviders.of(this).get(LolApiViewModel::class.java)
return view
}
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
summoner_search.setOnClickListener {
val summonerName = summoner_name.text.toString()
mViewModel.summonerIds(summonerName,apiKey).observe(viewLifecycleOwner,Observer<SummonerData>{
summoner_ID.text = it.id
Log.d("LolStatFragment", "LolStatFragment:" + it.id)
Toast.makeText(context, "zzzzzzzzz ${it.id}", Toast.LENGTH_SHORT).show()
})
}
}
}
here is the result of my retrofit request on a web browser:
{"id":"OR5-q4c9Mw3jKXcPZw2lXul0tT7eLf4dYNadYrGhQ9mG8-w","accountId":"gOb2ZjN51iRLnRmDJuR5GmfILqP3x-T3qfbKWaTZ9k3dYw","puuid":"9TgzR6qdI_X9Z6xFzV0nFndITN0LSGKKeJ5fol2Ii1a01l4duKvFwpYGJQvBeYkBLkvJc96Sr7DZMg","name":"Practice","profileIconId":4353,"revisionDate":1619525378251,"summonerLevel":209}
thank you to all those who will take the time to answer me !
PS:this is my first question on the forum, I hope to have been clear and to have asked my question correctly,If there's any detail that I left out for this question, feel free to ask.
I finally found the answer to my problem, the url of the network call was not formatted well. here is the code used to retrieve my call url api in my OnResponse method and compare it to that of the browser:
Log.d("LolApiRepository", "LolApiRepository:" + resp.toString())
this is what I had to change in my LolApiService interface :
public interface LolApiService {
#GET("summoners/by-name/{summonerName}?")
Call<SummonerData> getSummonerData (#Path("summonerName") String summonerName, #Query("api_key") String key);
}
I am trying to call an API using Retrofit in an Android application using Kotlin. The API requires a
a header and body similar to the following sample input:
Sample Input
Header:
loginName: 65848614-6697-4cf7-a64a-e0b9374c4aee
Body:
clientId: DKOKTrykIQ987yQcLNehT8SWJRMyQLdP
secret: 6Jt1ENlDn9gxPu5f
The content type has to be passed as application/x-www-form-urlencoded.
Currently, I am using the following classes:
YodleeService.kt
interface YodleeService {
#Headers(
"loginName: de5559cc-5375-4aca-8224-990343774c08_ADMIN",
"Api-Version: 1.1",
"Content-Type: application/x-www-form-urlencoded"
)
#POST("auth/token")
fun generateLoginToken(
#Body postBody: PostBody
) : Call<LoginToken>
}
AccountRetriever.kt
class AccountRetriever {
private val service: YodleeService
companion object {
const val BASE_URL = "https://sandbox.api.yodlee.com:443/ysl/"
}
init {
val retrofit = Retrofit.Builder()
.baseUrl(BASE_URL)
.addConverterFactory(GsonConverterFactory.create())
.build()
service = retrofit.create(YodleeService::class.java)
}
fun login(callback: Callback<LoginToken>) {
val postBody = PostBody("TG86ljAk6lt28GYZlRTQWssaLmGpS6jV", "A2P9ZPEqB4uos1nv")
val call = service.generateLoginToken(postBody)
call.enqueue(callback)
}
}
PostBody
data class PostBody(
val clientId: String?,
val secret: String?
)
MainActivity
class MainActivity : AppCompatActivity() {
private val accountRetriever = AccountRetriever()
private val loginCallback = object : Callback<LoginToken> {
override fun onFailure(call: Call<LoginToken>, t: Throwable) {
Log.e("MainActivity", "Problem calling Yodlee API {${t.message}")
}
override fun onResponse(call: Call<LoginToken>?, response: Response<LoginToken>?) {
response?.isSuccessful.let {
Log.i("MainActivity", "errorBody - Content = ${response?.raw()}")
val loginToken = LoginToken(
response?.body()?.accessToken ?: "",
response?.body()?.expiresIn ?: "",
response?.body()?.issuedAt ?: "")
}
}
}
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
accountsList.layoutManager = LinearLayoutManager(this)
if (isNetworkConnected()) {
accountRetriever.login(loginCallback)
} else {
AlertDialog.Builder(this).setTitle("No Internet Connection")
.setMessage("Please check your internet connection and try again")
.setPositiveButton(android.R.string.ok) { _, _ -> }
.setIcon(android.R.drawable.ic_dialog_alert).show()
}
}
private fun isNetworkConnected(): Boolean {
val connectivityManager =
getSystemService(Context.CONNECTIVITY_SERVICE) as ConnectivityManager
val activeNetwork = connectivityManager.activeNetwork
val networkCapabilities = connectivityManager.getNetworkCapabilities(activeNetwork)
return networkCapabilities != null &&
networkCapabilities.hasCapability(NetworkCapabilities.NET_CAPABILITY_INTERNET)
}
}
When I debug my application, I am getting a response of [size=213 text=\n {\n "errorCode": "Y303",\n …]. The documentation for the API says that this error code means the clientId or secret is missing.
When I dig through the debugger, I am seeing that the raw call reads as
Request {
method = POST, url = https: //sandbox.api.yodlee.com/ysl/auth/token,
tags = {
class retrofit2.Invocation =
com.example.budgettracker.api.YodleeService.generateLoginToken()[PostBody(
clientId = TG86ljAk6lt28GYZlRTQWssaLmGpS6jV, secret = A2P9ZPEqB4uos1nv)]
}
}
I cannot determine why the API is not seeing the POST body contents.
Any help would be greatly appreciated.
I am trying to fetch data from the server using retrofit get request, in the ViewModel, I initiate the request, OnResponse method of the request shows the data successfully being retrieved from the server but the observer in the fragment doesn't get updated. I am sharing the code below.
RETROFIT API CALL
fun getGenres(application: Context,callback:(List<Genre>)->Unit){
val baseURL = "https://listen-api.listennotes.com/"
var genreList: MutableLiveData<List<Genre>> =MutableLiveData()
val logging = HttpLoggingInterceptor()
// set your desired log level
logging.level = HttpLoggingInterceptor.Level.BODY
val httpClient = OkHttpClient.Builder()
// add your other interceptors …
// add logging as last interceptor
httpClient.addInterceptor(logging)
val gson = GsonBuilder()
.setLenient()
.create()
val retrofit = Retrofit.Builder()
.baseUrl(baseURL)
.addConverterFactory(GsonConverterFactory.create(gson))
.client(httpClient.build())
.build()
val api: ApiFunctions = retrofit.create(ApiFunctions::class.java)
val call: Call<PodcastGetCategoryResponse> = api.getGenres()
call.enqueue(object : Callback<PodcastGetCategoryResponse> {
override fun onFailure(call: Call<PodcastGetCategoryResponse>, t: Throwable) {
Toast.makeText(application, "failure" + t.stackTrace, Toast.LENGTH_SHORT).show()
}
override fun onResponse(
call: Call<PodcastGetCategoryResponse>,
response: Response<PodcastGetCategoryResponse>
) {
response.body().apply {
callback(this?.genres!!) }
Toast.makeText(application, "success: ${response.body()?.genres?.size}", Toast.LENGTH_SHORT).show()
}
})
return genreList;
}
This runs successfully and retrieves a list of Genres from the server.
VIEWMODEL CLASS
class CategoryViewModel(application: Application) : AndroidViewModel(application) {
private val rootJob = SupervisorJob()
private val coroutineContext: CoroutineContext
get() = Dispatchers.Main + rootJob
var listOfCategory: MutableLiveData<List<Genre>> = MutableLiveData()
init {
getistOfCategory()
}
// this method is responsible for retrieving data from the result of the API call method using a coroutine.
fun getistOfCategory() {
CoroutineScope(coroutineContext).launch() {
ApiFunctions.getGenres(getApplication<Application>(), { l -> listOfCategory.value = l } )
listOfCategory.postValue(listOfCategory.value)
}
}
I assume that issue lies in this class but I can't figure it out.
**FRAGMENT Class **
class MainFragment : Fragment() {
private lateinit var viewModel: CategoryViewModel
private lateinit var binding: FragmentMainBinding
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
viewModel = ViewModelProviders.of(this).get(CategoryViewModel::class.java)
viewModel.getistOfCategory()
}
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
binding =DataBindingUtil.inflate(inflater, R.layout.fragment_main, container, false)
var myView: View = binding.root
viewModel.listOfCategory.observe(this,
Observer { list ->
Toast.makeText(
context,
"Data Changed" + list?.size,
Toast.LENGTH_LONG
).show()
})
return myView
}
What I want is that when new values are retrieved from the server it should be saved in LiveData in ViewModel class and the fragment should successfully observe them.
according to your current implementation the value of listOfCategory keeps changing with each update. this means when your list is updated the observers are not being notified cause they're observing another LiveData object (which was assigned to your reference before the update occurred)
You need to make sure that you instantiate the liveData object only once and update its value whenever you get an update.
Your code should look something like this
fun getGenres(application: Context, callback:(List<Genre>)->Unit){
...
response.body().apply {
callback(this?.genres!!)
}
...
}
fun getistOfCategory(): {
CoroutineScope(coroutineContext).launch() {
ApiFunctions.getGenres(getApplication<Application>(), l -> listOfCategory.value = l)
}
}