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Android Kotlin Volley jsonObjectRequest always invoking VolleyError

Im trying to use Volley to get a JSON object from an API and then display it in a recyclerview using the MVVM Android.
Using Volley jsonObjectRequest Get request in the ModelView (SchoolViewModel) to get my data (JSON Object) parsed through Gson and pass it into my LiveData, then set up an observer in my View (MainFragment) to observe that data and keep updating it in the recycler.
Now the issue is that Volley is only invoking Error, "com.android.volley.ParseError: org.json.JSONException: Value [{"dbn":"02M260","school_name":"Clinton School.... "
I am not sure what is causing the parsing error, as it seems to be retrieving the JSON object as seen following by the error.
Any ideas why it's always jumping to VolleyError?
My View:
class MainFragment : Fragment() {
private lateinit var schoolViewModel: SchoolViewModel
private lateinit var linearLayoutManager: LinearLayoutManager
private var mainRecyclerAdapter: MainRecyclerAdapter = MainRecyclerAdapter()
//private var list: MutableList<MutableLiveData<SchoolsData>> = mutableListOf()
private var schoolsData = MutableLiveData<List<SchoolsData>>()
val API_Schools: String = "https://data.cityofnewyork.us/resource/s3k6-pzi2.json"
val API_SAT: String = "https://data.cityofnewyork.us/resource/f9bf-2cp4.json"
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
}
override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?) : View? {
// Inflate the layout for this fragment
val binding = FragmentMainBinding.inflate(layoutInflater)
schoolViewModel = ViewModelProvider(this).get(SchoolViewModel::class.java)
linearLayoutManager = LinearLayoutManager(context, RecyclerView.VERTICAL,false)
context?.let { schoolViewModel.getData(it) }
schoolViewModel._schoolsData.observe(viewLifecycleOwner, Observer{
mainRecyclerAdapter.setData(it)
} )
binding.recyclerMain.apply {
layoutManager = linearLayoutManager
adapter = mainRecyclerAdapter
}
return binding.root
}
}
ViewModel
class SchoolViewModel: ViewModel() {
private var schoolsData = MutableLiveData<List<SchoolsData>>()
val _schoolsData: LiveData<List<SchoolsData>> = schoolsData
private var satData = MutableLiveData<SATData>()
val _satData: LiveData<SATData> = satData
lateinit var jsonObjectRequest: JsonObjectRequest
val API_Schools: String = "https://data.cityofnewyork.us/resource/s3k6-pzi2.json"
val API_SAT: String = "https://data.cityofnewyork.us/resource/f9bf-2cp4.json"
fun getData(context: Context) {
val requestQueue: RequestQueue = Volley.newRequestQueue(context.applicationContext)
jsonObjectRequest = JsonObjectRequest(Request.Method.GET,API_Schools, null,
{
try {
val gson = Gson()
schoolsData = gson.fromJson(
it.toString(),
MutableLiveData<List<SchoolsData>>()::class.java
)
Log.e("RECEIVED", schoolsData.toString())
}catch (e: JSONException){
Log.e("JSONException", e.toString())
}
}, {
Log.e("ERROR",it.toString())
})
requestQueue.add(jsonObjectRequest)
}
}
Model
import com.google.gson.annotations.SerializedName
data class SchoolsData(
#SerializedName("dbn")
val id: String,
#SerializedName("school_name")
val school_name: String,
#SerializedName("total_students")
val students_num: Int,
#SerializedName("graduation_rate")
val graduation_rate: Float,
#SerializedName("primary_address_line_1")
val street: String,
#SerializedName("city")
val city: String
)

The JSON you are fetching is a JSONArray [{},{}] not a JSONObject, so you need to use JsonArrayRequest instead of JsonObjectRequest. Once you make that change, the volley error will go away, but you also need to update the parsing code - you should deserialize it to a List<SchoolsData>, not a MutableLiveData, like this:
val gson = Gson()
val listType = object : TypeToken<List<SchoolsData>>() {}.type
val schoolList = gson.fromJson<List<SchoolsData>>(
it.toString(),
listType
)
schoolsData.postValue(schoolList)

Kotlin Button to Load RecyclerView Data - Needs Two Presses

Firstly apologies for what i'm sure is a newby mistake somewhere. Just started learning Kotlin and likely thrown myself in the deep end, but i've got some understanding of what is happening.
My Context:
I'm using a button to load JSON data from a file on my server, before displaying it into a Recycler View.
The data loads fine into the recycler view list item nicely, but:
My Problem:
In order for the recyclerview to display the JSON data (which i'm getting with Volley), the button needs pressing twice.
On first press, nothing happens. Second press, the data updates.
I change the json on my server, press the button - nothing happens - recyclerview remains unchanged.
Press it again, and the recyclerview updates.
MainClass.kt
class MainActivity : AppCompatActivity() {
private var requestQueue: RequestQueue? = null
val serviceList: ArrayList<Service> = ArrayList()
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
val button: Button = findViewById(R.id.parsebtn)
val recycleradapter = Itemadapter(this, serviceList)
val recyclerview = findViewById<RecyclerView>(R.id.recycler)
recyclerview.adapter = recycleradapter
recyclerview.setHasFixedSize(true)
button.setOnClickListener {
jsonParse()
recycleradapter.notifyDataSetChanged()
}
requestQueue = Volley.newRequestQueue(this)
}
private fun jsonParse() {
val url = "MYSERVERIP/test.json"
val request = JsonObjectRequest(Request.Method.GET, url, null, Response.Listener {
response ->try {
serviceList.clear()
val jsonArray = response.getJSONArray("services")
for (i in 0 until jsonArray.length()) {
val serviceRow = jsonArray.getJSONObject(i)
val serviceOrigin = serviceRow.getString("origin")
val serviceDestination = serviceRow.getString("destination")
val serviceID = serviceRow.getString("train uid")
serviceList.add(Service(serviceOrigin, serviceDestination, serviceID))
}
} catch (e: JSONException) {
e.printStackTrace()
}
}, {
error -> error.printStackTrace()
})
requestQueue?.add(request)
}
}
Any help much appreciated. Thanks.
Adapter Class:
class Itemadapter (private val context: Context, private val dataset: ArrayList<Service>):
RecyclerView.Adapter<Itemadapter.ItemViewHolder>()
{
class ItemViewHolder(private val view: View): RecyclerView.ViewHolder(view){
val txtSOrigin: TextView = view.findViewById(R.id.serviceOrigin)
val txtSDest: TextView = view.findViewById(R.id.serviceDestination)
}
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ItemViewHolder {
val adapterLayout = LayoutInflater.from(parent.context)
.inflate(R.layout.list_item, parent, false)
return ItemViewHolder(adapterLayout)
}
override fun onBindViewHolder(holder: ItemViewHolder, position: Int) {
val item = dataset[position]
holder.txtSOrigin.text = item.sOrigin
holder.txtSDest.text = item.sDest
}
override fun getItemCount() = dataset.size
}
And then the service dataclass:
data class Service(var trainid: String, var sOrigin: String, var sDest: String)

REASON: This happens because the notifyDataSetChanged() is called as sequentially and actually then you don't have any data inside the serviceList, so it is more suitable to call that method after call has completed and a response has received
SOLUTION:
Conceptually, you should understand how asynchronous programming works.You misunderstood asynchronous programming with sequential execution and thus the above mistake
What now?
Move your recycleradapter.notifyDataSetChanged() to the place where you receive the response from the server like so in the Response.Listener interface instance
try {
serviceList.clear()
val jsonArray = response.getJSONArray("services")
for (i in 0 until jsonArray.length()) {
val serviceRow = jsonArray.getJSONObject(i)
val serviceOrigin = serviceRow.getString("origin")
val serviceDestination = serviceRow.getString("destination")
val serviceID = serviceRow.getString("train uid")
serviceList.add(Service(serviceOrigin, serviceDestination, serviceID))
recycleradapter.notifyDataSetChanged() // Here
}
} catch (e: JSONException) {
e.printStackTrace()
}
Also you can show certain kind of progress mechanism like a bar or a shimmer layout when the button is pressed and hide the visibility when the data is received from the server

Making HTTP request with Volley is asynchronous, so there is a big probability that the list of services is populated after notifying the adapter. So, you should refresh the RecyclerView when you actully got the result from the server:
response ->try {
serviceList.clear()
val jsonArray = response.getJSONArray("services")
for (i in 0 until jsonArray.length()) {
val serviceRow = jsonArray.getJSONObject(i)
val serviceOrigin = serviceRow.getString("origin")
val serviceDestination = serviceRow.getString("destination")
val serviceID = serviceRow.getString("train uid")
serviceList.add(Service(serviceOrigin, serviceDestination, serviceID))
}
runOnUiThread {
recycleradapter.notifyDataSetChanged()
}
} catch (e: JSONException) {
e.printStackTrace()
}

RecyclerView - notifyDataSetChanged() - Kotlin - Not Working

I am having an issue with reloading data in RecyclerView after the data is updated with a separate URL call. The FristFragment calls LoadDataFromUrl and displays the data in the Recycler View. Each Recycler's view item has a button with OnSetClickListener that calls another URL to update item's name data. After the user updates the item's name and a successful response is received, then the original myResponse data is updated with the new item's name. When the data is updated, I need to reload data in the Recycer View` but I can not figure it out. I spent two days trying to fix it but I can't get it running. Any help would be greatly appreciated!
Data Model:
DataModel.kt
class MyResponse (var Status: String = "", val items: List<Items> = emptyList())
class Items(var ItemId: String = "", var ItemName: String = "")
Code for Recycler View:
Adapter.kt
var recyclerView: RecyclerView? = null
class MainAdapter(val myResponse: MyResponse): RecyclerView.Adapter<CustomViewHolder>(){
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): CustomViewHolder {
val layoutInflater = LayoutInflater.from(parent?.context)
val cellForRow = layoutInflater.inflate(R.layout.my_custom_cell, parent,false)
return CustomViewHolder(cellForRow)
}
override fun onBindViewHolder(holder: CustomViewHolder, position: Int) {
val item = myResponse.items.get(position)
//there is a button for each item in the list that will call a function ButtonPressed from Frist Fragment
holder.view.button.setOnClickListener {
val firstFragment = FirstFragment()
firstFragment.ButtonPressed(item.ItemId,item.ItemName, position)
}
holder.view.textView_ItemID = item.itemId
holder.view.textView_Item_Name = item.itemName
}
class CustomViewHolder(val view: View, var Items: Item? = null): RecyclerView.ViewHolder(view){
}
}
Then I have a fragment Fragment.kt
FirstFragment.kt
class FirstFragment : Fragment() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
}
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
val rootView = inflater.inflate(R.layout.first_fragment, container, false)
return rootView
}
override fun onActivityCreated(savedInstanceState: Bundle?) {
super.onActivityCreated(savedInstanceState)
LoadDataFromUrl()
recyclerView.layoutManager = LinearLayoutManager(this.context,
LinearLayoutManager.HORIZONTAL, false)
}
//this function loads data on create view
fun LoadDataFromUrl(){
val url = "some_url"
val payload = "some_data_to_send"
val requestBody = payload.toRequestBody()
val request = Request.Builder()
.method("POST",requestBody)
.url(url)
.build()
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) {
val body = response?.body?.string()
val gson = GsonBuilder().create()
myResponse = gson.fromJson(body, MyResponse::class.java)
activity?.runOnUiThread {
if (myResponse.Status== "200"){
recyclerView.adapter = MainAdapter(myResponse)
}
}
}
})
}
fun ButtonPressed(itemId: String, itemName: String, position: Int){
val url = "some_another_url"
val payload = "some_another_data_to_send"
val requestBody = payload.toRequestBody()
val request = Request.Builder()
.method("POST",requestBody)
.url(url)
.build()
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) {
val body = response?.body?.string()
val gson = GsonBuilder().create()
val buttomPressedResponse = gson.fromJson(body, ButtonPressedResponse::class.java)
if (buttonPressedResponse.Status== "200") {
myResponse.response[position].Status = buttomPressedResponse.Status //will update existing object myResponse with a new item's name
//this is where I have a problem
recyclerView.adapter.notifyDataSetChanged()
}
}
}
}
I tried the following changes but I still get an error.
//I get this error: Fatal Exception: OkHttp Dispatcher Process. recyclerView must not be null. Then the app crashes and the view reloads. If I clcik the Button again I get an error saying: RecyclerView: No adapter atatched. Skipping layout.
activity?.runOnUiThread {
myResponse.response[position].Status = checkInOutResponse.Status //will update existing object myResponse with updated data
recyclerView.adapter?.notifyDataSetChanged()
}
I also tried to run on it runOnUiTHread but nothing happens with this code
activity?.runOnUiThread {
myResponse.response[position].Status = checkInOutResponse.Status //will update existing object myResponse with updated data
recyclerView.adapter?.notifyDataSetChanged()
}

Create var myResponse: MyResponse variable in Adapter
Adapter.kt
var recyclerView: RecyclerView? = null
class MainAdapter(val myResponseInit: MyResponse): RecyclerView.Adapter<CustomViewHolder>(){
var myResponse: MyResponse
myResponse = myResponseInit
fun submitMyResponse(data: MyResponse) {
myResponse = data
}
//Rest of the code onCreateViewHolder etc.
}
Call submitMyResponse() function and notifyDataSetChanged() on adapter everytime you receive response.

RecyclerView make endless scrolling with JSON

I'm trying to make my Android App (I'm only experienced in iOS).
I created a RecyclerView that gets the data from a web. I tried everything to implement endless scrolling to load more items, but when I call the function to get the items, the entire RecyclerView loads again and no attach the new results on the bottom.
This is my code:
ConversationUser.kt
data class ConversationUser(
val message_nickname: String,
val message_image_thumb: String,
val message_large_thumb: String,
val message_modified: String,
val message_status: String,
val message_unread: Int,
val conv_id: String,
val message_dest: String) {
}
ConversacionesActivity.kt
class ConversacionesActivity : AppCompatActivity() {
// MARK: Variables
var user_token = ""
var user_id = ""
override fun onCreate(savedInstanceState: Bundle?) {
// User Defaults
val sharedPreferences = getSharedPreferences("Preferences", Context.MODE_PRIVATE)
user_token = sharedPreferences.getString("user_token", "")!!
user_id = sharedPreferences.getString("user_id", "")!!
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_conversaciones)
recyclerConv.addItemDecoration(DividerItemDecoration(this, LinearLayoutManager.VERTICAL))
getConversationsData()
recyclerConv.setLoadingListener(object : LoadingListener {
override fun onRefresh() {
//refresh data here
}
override fun onLoadMore() {
// load more data here
getConversationsData()
}
})
}
fun getConversationsData() {
val httpAsync = "https://mywebsite.com/conversations/${user_token}"
.httpPost()
.responseString { request, response, result ->
when (result) {
is Result.Failure -> {
val ex = result.getException()
println(ex)
}
is Result.Success -> {
val data = result.get()
runOnUiThread {
val conversaciones = processJson(data)
show(conversaciones)
return#runOnUiThread
}
}
}
}
httpAsync.join()
}
fun processJson(json: String): List<ConversationUser> {
val gson: Gson = GsonBuilder().create()
val conversaciones: List<ConversationUser> = gson.fromJson(
json,
Array<ConversationUser>::class.java
).toList()
return conversaciones
}
fun show(conversaciones: List<ConversationUser>) {
recyclerConv.layoutManager = LinearLayoutManager(this, LinearLayoutManager.VERTICAL, false)
recyclerConv.adapter = AdaptadorConv(conversaciones, this, user_token, user_id)
}
AdaptadorConv.kt
class AdaptadorConv(
val conversaciones: List<ConversationUser> = ArrayList(),
val context: Context,
val user_token: String,
val user_id: String) : RecyclerView.Adapter<AdaptadorConv.ConvViewHolder>() {
override fun onBindViewHolder(holder: ConvViewHolder, position: Int) {
holder.convName.text = conversaciones[position].message_nickname
holder.convTime.text = conversaciones[position].message_modified
}
override fun getItemCount(): Int {
return conversaciones.size - 1
}
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ConvViewHolder {
val view: View = LayoutInflater.from(parent.context).inflate(
R.layout.conversaciones,
parent,
false
)
return ConvViewHolder(view)
}
class ConvViewHolder(vista: View): RecyclerView.ViewHolder(vista) {
val convImg: ImageView = itemView.findViewById(R.id.convImg)
val convStatus: ImageView = itemView.findViewById(R.id.convStatus)
val convName: TextView = itemView.findViewById(R.id.convName)
val convUnread: TextView = itemView.findViewById(R.id.convUnread)
val convTime: TextView = itemView.findViewById(R.id.convTime)
}
Thanks for any help or hint.

Please check your show () method, you are creating new Adapter every time with the new dataset. You have to append the new items to the adapter's list and adapter should be set to list once. Helpful tutorial can be found at here.

How to wait and execute code after AsyncHttpClient() Done?

I want to take data from API using AsyncHttpClient(), after that, I show the data to recycle view. but when trying to debug my code is run show the data to recycle view which is no data because not yet finish setData using AsyncHttpClient(). my question is how to run setData recycle view adapter after my setLeague is finish getting data? Sorry, I am a newbie and I put my code below. Please help, I already try using async-await but doesn't work.
This is my ViewModel Class
val footballLeagueList = MutableLiveData<ArrayList<league>>()
internal fun setLeague(){
val client = AsyncHttpClient()
val client2 = AsyncHttpClient()
val listItems = ArrayList<league>()
val leagueListUrl = "https://www.thesportsdb.com/api/v1/json/1/all_leagues.php"
val leagueDetailUrl = "https://www.thesportsdb.com/api/v1/json/1/lookupleague.php?id="
client.get(leagueListUrl, object : AsyncHttpResponseHandler(){
override fun onSuccess(
statusCode: Int,
headers: Array<out Header>?,
responseBody: ByteArray?
) {
try{
val result = String(responseBody!!)
val responseObject = JSONObject(result)
for(i in 0 until 10){
val list = responseObject.getJSONArray("leagues")
val leagues = list.getJSONObject(i)
val leaguesItems = league()
val detailUrl = leagueDetailUrl + leagues.getString("idLeague")
leaguesItems.id = leagues.getString("id")
leaguesItems.name = leagues.getString("strLeague")
leaguesItems.badgeUrl = leagues.getString( "https://www.thesportsdb.com/images/media/league/badge/dqo6r91549878326.png")
listItems.add(leaguesItems)
}
footballLeagueList.postValue(listItems)
}catch (e: Exception){
Log.d("Exception", e.message.toString())
}
}
override fun onFailure(
statusCode: Int,
headers: Array<out Header>?,
responseBody: ByteArray?,
error: Throwable?
) {
Log.d("Failed", "On Failure")
}
})
}
internal fun getLeague(): LiveData<ArrayList<league>> {
return footballLeagueList
}
And this is my MainActivity
class MainActivity : AppCompatActivity() {
private lateinit var mainViewModel: MainViewModel
private lateinit var adapterLeague: leagueAdapter
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
adapterLeague = leagueAdapter()
adapterLeague.notifyDataSetChanged()
verticalLayout {
lparams(matchParent, matchParent)
recyclerView {
layoutManager = GridLayoutManager(context, 2)
adapter = adapterLeague
}
}
mainViewModel = ViewModelProvider(this, ViewModelProvider.NewInstanceFactory())
.get(MainViewModel::class.java)
mainViewModel.setLeague()
mainViewModel.getLeague().observe(this, Observer { leaguesItems ->
if(leaguesItems != null){
adapterLeague.setData(leaguesItems)
}
})
}
}