Develop Reference

How can I initialize in onResponse function? (Android Kotlin)

I thought when response.body()?.let {} run, enrollBookAdapter (or booklist = it.books as mutableList<book>) would be initialized but, it did not... What am I doing wrong? How can I initailize bookList with Books...
class EnrollBookActivity : AppCompatActivity() {
private lateinit var binding: ActivityEnrollBookBinding
private lateinit var bookService: BookService
private lateinit var bookList:MutableList<Book>
private lateinit var enrollBookAdapter: EnrollBookAdapter
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
binding = ActivityEnrollBookBinding.inflate(layoutInflater)
setContentView(binding.root)
initBookService()
bookServiceLoadBestSellers()
binding.selfBtn.setOnClickListener{
startActivity(Intent(this,SelfWriteActivity::class.java))
}
enrollBookAdapter.setOnBookClickListener(object:EnrollBookAdapter.OnBookClickListener{
override fun onBookClick(position: Int, book: Book) {
val intent = Intent(this#EnrollBookActivity,TalerMain::class.java)
intent.putExtra("title",enrollBookAdapter.bookList[position].title)
intent.putExtra("url",enrollBookAdapter.bookList[position].title)
startActivity(intent)
}
})
}
private fun initBookRecyclerView(bookList: MutableList<Book>) {
enrollBookAdapter = EnrollBookAdapter(bookList)
enrollBookAdapter.setOnBookClickListener(object:EnrollBookAdapter.OnBookClickListener{
override fun onBookClick(position: Int, book: Book) {
val intent = Intent(this#EnrollBookActivity,TalerMain::class.java)
intent.putExtra("title",enrollBookAdapter.bookList[position].title)
intent.putExtra("url",enrollBookAdapter.bookList[position].title)
startActivity(intent)
}
})
binding.bookRv.layoutManager = GridLayoutManager(this,2)
binding.bookRv.adapter = EnrollBookAdapter(bookList)
binding.bookRv.addItemDecoration(DividerItemDecoration(this, LinearLayoutManager.VERTICAL))
}
private fun bookServiceLoadBestSellers() {
bookService.getBestSellerBooks(getString(R.string.interparkAPIKey))
.enqueue(object : Callback<BestSellerDto> {
override fun onResponse(
call: Call<BestSellerDto>,
response: Response<BestSellerDto>
) {
if (response.isSuccessful.not()) {
Log.e(M_TAG, "NOT!! SUCCESS")
return
}
response.body()?.let {
Log.d(M_TAG, it.toString())
it.books.forEach { book ->
Log.d(M_TAG, book.toString())
}
//enrollBookAdapter = EnrollBookAdapter(it.books as MutableList<Book>)
initBookRecyclerView(it.books as MutableList<Book>)
//setRecyclerView(it.books)
}
}
override fun onFailure(call: Call<BestSellerDto>, t: Throwable) {
Log.e(M_TAG, t.toString())
}
})
}
}
Error
"java.lang.RuntimeException: Unable to start activity ComponentInfo{com.clone.practice/com.clone.practice.EnrollBookActivity}: kotlin.UninitializedPropertyAccessException: lateinit property enrollBookAdapter has not been initialized"
I thought when response.body()?.let {} run, enrollBookAdapter (or booklist = it.books as mutableList<book>) would be initialized but, it did not... What am I doing wrong? How can I initialize bookList with Books...

Try to add initBookRecyclerView before enrollBookAdapter.setOnBookClickListener(object:EnrollBookAdapter.OnBookClickListener line in onCreate.
After that uncomment enrollBookAdapter = EnrollBookAdapter(it.books as MutableList<Book>) and comment the next line.

just remove this code from your onCreate method only as you are trying to use enrollBookAdapter variable before initialisation which is causing crash .
And you have already set this method in initBookRecyclerView method so no need in onCreate method
enrollBookAdapter.setOnBookClickListener(object:EnrollBookAdapter.OnBookClickListener{
override fun onBookClick(position: Int, book: Book) {
val intent = Intent(this#EnrollBookActivity,TalerMain::class.java)
intent.putExtra("title",enrollBookAdapter.bookList[position].title)
intent.putExtra("url",enrollBookAdapter.bookList[position].title)
startActivity(intent)
}
})

java.lang.InstantiationException: java.lang.Class<com.example.exampleproject.ExampleActivity> has no zero argument constructor [closed]

Closed. This question needs debugging details. It is not currently accepting answers.
Edit the question to include desired behavior, a specific problem or error, and the shortest code necessary to reproduce the problem. This will help others answer the question.
Closed 1 year ago.
Improve this question
When i run my app its showing me (InstantiationException:has no zero argument constructor) and ask for create a zero argument constructor, I am new in kotlin please suggest me how i can solve it.
Login Activity:-
class LoginActivity(val ViewModelProvider: Any) : AppCompatActivity(), AuthListenner {
private val listview: ListView? = null
private val progressBar: ProgressBar? = null
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_login)
}
override fun onStarted() {
toast("Login Started")
}
override fun onSuccess(logingResponse: LiveData<String>) {
toast("Login Success")
}
override fun onFailure(message: String) {
toast(message)
}
}
This is my Model Class:-
class AuthViewModel() : ViewModel() {
var username: String? = null
var password:String? = null
var authListenner: AuthListenner? = null
fun onLoginButtonClick(View: View){
authListenner?.onStarted()
if (username.isNullOrEmpty() || password.isNullOrEmpty()){
authListenner?.onFailure("Invalid username or password")
return
}
val logingResponse = UserRepository().userLogin(username!!, password!!)
authListenner?.onSuccess(logingResponse)
}
}
class UserRepository {
fun userLogin(username: String, password: String) : LiveData<String> {
val loginResponse = MutableLiveData<String>()
MyApi().userLogin(username, password)
.enqueue(object : Callback<ResponseBody> {
override fun onFailure(call: Call<ResponseBody>, t: Throwable) {
loginResponse.value = t.message
}
override fun onResponse(call: Call<ResponseBody>, response: Response<ResponseBody>) {
if (response.isSuccessful){
loginResponse.value = response.body()?.string()
}else{
loginResponse.value = response.errorBody()?.string()
}
}
})
return loginResponse
}
}
interface AuthListenner {
fun onStarted()
fun onSuccess(logingResponse: LiveData<String>)
fun onFailure(message: String)
}

Can't add para to the AppCompatActivity, it should be
class LoginActivity: AppCompatActivity(), AuthListenner {
//...
}

onResume does not worked in viewmodel

my data is fetched only when it is created...im using viewmodel...when press back button it doesnt update the previous data..onresume is not working in this...
i refered this but none of those helped--> Reacting to activity lifecycle in ViewModel
i need help
thanks in advance
activity:--
class MyAccount : BaseClassActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.myaccount)
var mActionBarToolbar = findViewById<androidx.appcompat.widget.Toolbar>(R.id.toolbartable);
setSupportActionBar(mActionBarToolbar);
setEnabledTitle()
val resetbutton=findViewById<Button>(R.id.resetpwd)
resetbutton.setOnClickListener {
val i=Intent(applicationContext,
ResetPasswordActivity::class.java)
startActivity(i)
}
val editbutton=findViewById<Button>(R.id.editdetail)
editbutton.setOnClickListener {
val i=Intent(applicationContext, EditProfile::class.java)
startActivity(i)
}
hello()
}
override fun onResume() {
super.onResume()
hello()
}
fun hello(){
val first_name = findViewById<TextView>(R.id.firstname)
val last_name = findViewById<TextView>(R.id.lastname)
val emailuser = findViewById<TextView>(R.id.emailuser)
val phone_no = findViewById<TextView>(R.id.phone_no)
val birthday = findViewById<TextView>(R.id.birthday)
val image=findViewById<ImageView>(R.id.imageprofile)
val model = ViewModelProvider(this)[MyAccountViewModel::class.java]
model.viewmodel?.observe(this, object : Observer<My_account_base_response> {
override fun onChanged(t: My_account_base_response?) {
first_name.setText(t?.data?.user_data?.first_name)
last_name.setText(t?.data?.user_data?.last_name)
emailuser.setText(t?.data?.user_data?.email)
phone_no.setText(t?.data?.user_data?.phone_no).toString()
birthday.setText(t?.data?.user_data?.dob).toString()
Glide.with(applicationContext).load(t?.data?.user_data?.profile_pic)
.diskCacheStrategy(DiskCacheStrategy.ALL)
.placeholder(R.drawable.ic_launcher_foreground)
.into(image)
}
})
}
override fun onOptionsItemSelected(item: MenuItem): Boolean {
return when (item.itemId) {
android.R.id.home -> {
NavUtils.navigateUpFromSameTask(this)
true
}
else -> super.onOptionsItemSelected(item)
}
}}
viewmodel:--
class MyAccountViewModel(context: Application) :AndroidViewModel(context),LifecycleObserver{
private var MyAccountViewModels: MutableLiveData<My_account_base_response>? = null
val viewmodel: MutableLiveData<My_account_base_response>?
get() {
if (MyAccountViewModels == null) {
MyAccountViewModels = MutableLiveData<My_account_base_response>()
loadviewmodel()
}
return MyAccountViewModels
}
private fun loadviewmodel(){
val token :String = SharedPrefManager.getInstance(getApplication()).user.access_token.toString()
RetrofitClient.instance.fetchUser(token)
.enqueue(object : Callback<My_account_base_response> {
override fun onFailure(call: Call<My_account_base_response>, t: Throwable) {
Log.d("res", "" + t)
}
override fun onResponse(
call: Call<My_account_base_response>,
response: Response<My_account_base_response>
) {
var res = response
if (res.body()?.status == 200) {
MyAccountViewModels!!.value = response.body()
} else {
try {
val jObjError =
JSONObject(response.errorBody()!!.string())
Toast.makeText(getApplication(),
jObjError.getString("user_msg"),
Toast.LENGTH_LONG).show()
} catch (e: Exception) {
Log.e("errorrr", e.message)
}
}
}
})
}}

There are bunch of things wrong here, so let me provide you refactored code and explanation as much as I would be able to..
Activity:
class MyAccount : BaseClassActivity() {
private val mActionBarToolbar by lazy { findViewById<androidx.appcompat.widget.Toolbar>(R.id.toolbartable) }
private val resetbutton by lazy { findViewById<Button>(R.id.resetpwd) }
private val editbutton by lazy { findViewById<Button>(R.id.editdetail) }
private val first_name by lazy { findViewById<TextView>(R.id.firstname) }
private val last_name by lazy { findViewById<TextView>(R.id.lastname) }
private val emailuser by lazy { findViewById<TextView>(R.id.emailuser) }
private val phone_no by lazy { findViewById<TextView>(R.id.phone_no) }
private val birthday by lazy { findViewById<TextView>(R.id.birthday) }
private val image by lazy { findViewById<ImageView>(R.id.imageprofile) }
lateinit var model: MyAccountViewModel
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.myaccount)
setSupportActionBar(mActionBarToolbar)
setEnabledTitle()
model = ViewModelProvider(this)[MyAccountViewModel::class.java]
resetbutton.setOnClickListener {
val i = Intent(applicationContext, ResetPasswordActivity::class.java)
startActivity(i)
}
editbutton.setOnClickListener {
val i = Intent(applicationContext, EditProfile::class.java)
startActivity(i)
}
model.accountResponseData.observe(this, object : Observer<My_account_base_response> {
override fun onChanged(t: My_account_base_response?) {
first_name.setText(t?.data?.user_data?.first_name)
last_name.setText(t?.data?.user_data?.last_name)
emailuser.setText(t?.data?.user_data?.email)
phone_no.setText(t?.data?.user_data?.phone_no).toString()
birthday.setText(t?.data?.user_data?.dob).toString()
Glide.with(applicationContext)
.load(t?.data?.user_data?.profile_pic)
.diskCacheStrategy(DiskCacheStrategy.ALL)
.placeholder(R.drawable.ic_launcher_foreground)
.into(image)
}
})
}
override fun onResume() {
super.onResume()
model.loadAccountData()
}
override fun onOptionsItemSelected(item: MenuItem): Boolean {
return when (item.itemId) {
android.R.id.home -> {
NavUtils.navigateUpFromSameTask(this)
true
}
else -> super.onOptionsItemSelected(item)
}
}
}
Few notes on your activity class:
You don't need to findViewById everytime, just do it once during onCreate or do it lazily. (FYI consider using kotlin synthetics or view binding or data binding)
Initialize your viewModel during onCreate method only. (That's the best way to do it)
Also observer your LiveData from ViewModel once, it should be also from the onCreate as it's the entry point to the activity and apart from config changes this method called only once. So, it's safe to observe it over there rather than during onResume which will be called multiple times during activity lifecycle. (The main issue your code wasn't working, so as a fix you only call your API method from ViewModel during resume)
ViewModel:
class MyAccountViewModel(context: Application) : AndroidViewModel(context) {
private val _accountResponseData = MutableLiveData<My_account_base_response?>()
val accountResponseData: MutableLiveData<My_account_base_response?>
get() = _accountResponseData
init {
loadAccountData()
}
fun loadAccountData() {
val token: String = SharedPrefManager.getInstance(getApplication()).user.access_token.toString()
RetrofitClient.instance.fetchUser(token)
.enqueue(object : Callback<My_account_base_response> {
override fun onFailure(call: Call<My_account_base_response>, t: Throwable) {
Log.d("res", "" + t)
_accountResponseData.value = null
}
override fun onResponse(
call: Call<My_account_base_response>,
response: Response<My_account_base_response>
) {
var res = response
if (res.body()?.status == 200) {
_accountResponseData.value = response.body()
} else {
try {
val jObjError =
JSONObject(response.errorBody()!!.string())
Toast.makeText(
getApplication(),
jObjError.getString("user_msg"),
Toast.LENGTH_LONG
).show()
} catch (e: Exception) {
Log.e("errorrr", e.message)
}
}
}
})
}
}
Don't make initial API call along with LiveData creation, it's okay to do in most of cases but if you're updating LiveData on response of that call then it's good to make it separately like during init block.
It's good practice not to allow Ui (Activity/Fragments) to modify LiveDatas of ViewModel directly. So, that's good sign you're following such pattern by having private MutableLiveData exposed as public LiveData, but do it correctly as suggested.
Side note: Your view model doesn't need to be LifecycleObserver. LifecycleObserver is used for some custom class/component which needs to be managed by their self by silently observing/depending on activity lifecycle independently. That's not the use case of ViewModel.
The only thing that I found why your code wasn't working correctly is because you were creating & observing ViewModel & LiveData over & over again as new objects from onResume method where you called hello() method.
Let me know if something don't make sense or missing.

How to make synchronous call in Coroutine

I want to make my network request synchronous because the input of second request comes from the output of first request.
override fun onCreate(savedInstanceState: Bundle?) {
retrofit1 =Retrofit.Builder()
.baseUrl("https://jsonplaceholder.typicode.com/").addConverterFactory(GsonConverterFactory.create()).build()
retrofit2 =Retrofit.Builder()
.baseUrl("https://samples.openweathermap.org/").addConverterFactory(GsonConverterFactory.create()).build()
button.setOnClickListener { view ->
CoroutineScope(IO).launch {
fakeApiRequest()
}}
In my fakeApiRequest(),I am making two network request.
private suspend fun fakeApiRequest() {
val result1 :Geo?= getResult1FromApi()
val result2: Long? = getResult2FromApi(result1)}
Since,this is an asynchronous call,I am getting Null Pointer Exception in my getResult2FromApi(result1) method because the argument passed is null.
In order to fix this issue,I had to add delay(1500) in first call.
private suspend fun getResult1FromApi(): Geo? {
val service:CallService = retrofit1!!.create(CallService::class.java)
val call = service.getUsers()
call.enqueue(object : Callback<List<User>> {
override fun onResponse(call: Call<List<User>>, response: Response<List<User>>) {
g = users.get(0).address.geo
}
override fun onFailure(call: Call<List<User>>, t: Throwable) {
}
})
delay(1500)
return g
}
-----------------------------------------------------------
private suspend fun getResult2FromApi(result1: Geo?): Long? {
val service2:CallService = retrofit2!!.create(CallService::class.java)
val call2 = service2.getWeather(result1?.lat!!, result1.lng,"b6907d289e10d714a6e88b30761fae22")
call2.enqueue(object : Callback<WeatherData> {
override fun onResponse(call: Call<WeatherData>, response: Response<WeatherData>) {
}
override fun onFailure(call: Call<WeatherData>, t: Throwable) {
}
})
return dt
}
Is there anyway I can make this synchronous, so that I don't have to pass any delay time.

You haven't implemented the suspendable function correctly. You must use suspendCoroutine:
suspend fun getResult1FromApi(): Geo? = suspendCoroutine { continuation ->
val service = retrofit1!!.create(CallService::class.java)
service.getUsers().enqueue(object : Callback<List<User>> {
override fun onResponse(call: Call<List<User>>, response: Response<List<User>>) {
continuation.resume(response.result.getOrNull(0)?.address?.geo)
}
override fun onFailure(call: Call<List<User>>, t: Throwable) {
continuation.resumeWithException(t)
}
})
}
Now your function is synchronous and returns a Geo object.

How to get a variable from another class in kotlin?

I want to get a variable from an activity and use it in another class.
This variable will be filled by an user in a editText that is called editTextSerie
override fun searchSeries(listener: OnDataListener) {
val retrofit = Retrofit.Builder().addConverterFactory(GsonConverterFactory.create())
.baseUrl("http://api.themoviedb.org/3/")
.build()
val client = retrofit.create(MovieDBApiInterface::class.java)
val objetoClasse1 = SearchActivity()
var nomeS = objetoClasse1.editTextSerie.text.toString().trim()
val responseCall = client.searchSeries("API_KEY", "pt-BR", nomeS)
responseCall.enqueue(object : Callback<AllSeriesResponse> {
override fun onResponse(call: Call<AllSeriesResponse>?, response1: Response<AllSeriesResponse>?) {
listener.onSuccess(response1!!.body()!!.results)
}
override fun onFailure(call: Call<AllSeriesResponse>?, t: Throwable?) {
listener.onFailure(t!!.message.toString())
}
})
}
This function "searchSeries" is from the class "Series".
I want to get the "editTextSerie" from another class called "Search Activity",
so i created the variable "nomeS" to receive the value of it.
class SearchActivity : AppCompatActivity() {
var botaoSearch: AppCompatImageButton? = null
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_search)
botaoSearch = findViewById(R.id.btn_search)
botaoSearch?.setOnClickListener {
var nomeSerie = editTextSerie.text.toString().trim()
}
}
}
I want to receive this value (value of editTextSerie comes from the XML of SearchActivity ) and use it at responseCall with the "nomeS" variable

What is OnDataListener? Not really sure it is interface or abstract class, so I' ll write some pseudo code.
First change your function searchSeries's params to
searchSeries(text: String, listener: OnDataListener)
So in the class Series, you can get the data in your function searchSeries:
override fun searchSeries(text: String, listener: OnDataListener) {
// ...
// you can get the "text" string
}
Then edit your SearActivity's listener:
class SearchActivity : AppCompatActivity() {
var botaoSearch: AppCompatImageButton? = null
// create class "Series"
val series = Series()
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_search)
botaoSearch = findViewById(R.id.btn_search)
botaoSearch?.setOnClickListener {
var nomeSeries = editTextSerie.text.toString().trim()
searchSeries(nomeSeries)
}
}
private fun searchSeries(text: String) {
series.searchSeries(text, object : OnDataListener {
override onSuccess(a0: ...) {
}
override onFailure(message: String) {
}
})
}
}
If OnDataListener is a abstract class:
series.searchSeries(text, object : OnDataListener() {
override onSuccess(a0: ...) {
}
override onFailure(message: String) {
}
})