Develop Reference

Android "Failed to open APK ", "failed to add asset path" & "java.io.IOException: Failed to load asset path"

Failed to open APK '/data/app/~~Binr6SVO9dmLCUcPgCpAyA==/com.example.newspaper-yFV7fjvEt5i0gI4--yMcTA==/base.apk': I/O error
Failed to open APK '/data/app/~~Binr6SVO9dmLCUcPgCpAyA==/com.example.newspaper-yFV7fjvEt5i0gI4--yMcTA==/base.apk': I/O error
failed to add asset path '/data/app/~~Binr6SVO9dmLCUcPgCpAyA==/com.example.newspaper-yFV7fjvEt5i0gI4--yMcTA==/base.apk'
java.io.IOException: Failed to load asset path /data/app/~~Binr6SVO9dmLCUcPgCpAyA==/com.example.newspaper-yFV7fjvEt5i0gI4--yMcTA==/base.apk
at android.content.res.ApkAssets.nativeLoad(Native Method)
at android.content.res.ApkAssets.(ApkAssets.java:295)
at android.content.res.ApkAssets.loadFromPath(ApkAssets.java:144)
at android.app.ResourcesManager.loadApkAssets(ResourcesManager.java:454)
at android.app.ResourcesManager.access$000(ResourcesManager.java:72)
at android.app.ResourcesManager$ApkAssetsSupplier.load(ResourcesManager.java:168)
at android.app.ResourcesManager.createAssetManager(ResourcesManager.java:530)
at android.app.ResourcesManager.createResourcesImpl(ResourcesManager.java:612)
at android.app.ResourcesManager.findOrCreateResourcesImplForKeyLocked(ResourcesManager.java:664)
at android.app.ResourcesManager.createResources(ResourcesManager.java:1011)
at android.app.ResourcesManager.getResources(ResourcesManager.java:1114)
at android.app.ActivityThread.getTopLevelResources(ActivityThread.java:2414)
at android.app.ApplicationPackageManager.getResourcesForApplication(ApplicationPackageManager.java:1751)
at android.app.ApplicationPackageManager.getResourcesForApplication(ApplicationPackageManager.java:1737)
at android.app.ApplicationPackageManager.getDrawable(ApplicationPackageManager.java:1506)
at android.app.ApplicationPackageManager.loadUnbadgedItemIcon(ApplicationPackageManager.java:3029)
at android.content.pm.PackageItemInfo.loadUnbadgedIcon(PackageItemInfo.java:290)
at com.android.systemui.toast.SystemUIToast.getBadgedIcon(SystemUIToast.java:284)
at com.android.systemui.toast.SystemUIToast.inflateToastView(SystemUIToast.java:198)
at com.android.systemui.toast.SystemUIToast.(SystemUIToast.java:90)
at com.android.systemui.toast.SystemUIToast.(SystemUIToast.java:77)
at com.android.systemui.toast.ToastFactory.createToast(ToastFactory.java:78)
at com.android.systemui.toast.ToastUI.lambda$showToast$0(ToastUI.java:113)
at com.android.systemui.toast.ToastUI.$r8$lambda$w_gPCh3F8Xxn1jN4lkQZoUci71c(Unknown Source:0)
at com.android.systemui.toast.ToastUI$$ExternalSyntheticLambda0.run(Unknown Source:16)
at com.android.systemui.toast.ToastUI.showToast(ToastUI.java:140)
at com.android.systemui.statusbar.CommandQueue$H.handleMessage(CommandQueue.java:1441)
at android.os.Handler.dispatchMessage(Handler.java:106)
at android.os.Looper.loopOnce(Looper.java:201)
at android.os.Looper.loop(Looper.java:288)
at android.app.ActivityThread.main(ActivityThread.java:7842)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:548)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1003)
I'm using the News API for my news app. These are the steps until the crash :
Showing a list of news
Click on one of them to show its details into the ArticleFragment
When I click on the floatingactionbutton to save it in the SavedNewsFragment, it crashes with the mentioned error.
The related files :
NewsViewModel
class NewsViewModel(val repo : NewsRepository) : ViewModel()
{
val breakingNews: MutableLiveData<Resource<NewsResponse>> = MutableLiveData()
val breakingNewsPage = 1 // update later
val searchNews: MutableLiveData<Resource<NewsResponse>> = MutableLiveData()
val searchNewsPage = 1 // update later
var savedNews: MutableLiveData<List<Article>> = MutableLiveData()
init {
getBreakingNews()
}
/**For BreakingNewsFragment**/
private fun getBreakingNews(countryString : String = "eg") = viewModelScope.launch {
breakingNews.postValue(Resource.Loading())
val response = repo.getBreakingNews(countryString, breakingNewsPage)
breakingNews.postValue(handleBreakingNewsResponse(response))
}
private fun handleBreakingNewsResponse(response: Response<NewsResponse>) : Resource<NewsResponse>
{
if(response.isSuccessful)
response.body().let {
return Resource.Success(it)
}
else
return Resource.Error(response.message(), response.body())
}
/**For SearchNewsFragment**/
fun searchForNews(text : String) = viewModelScope.launch {
searchNews.postValue(Resource.Loading())
val response = repo.getSearchedNews(text, searchNewsPage)
searchNews.postValue(handleSearchForNewsResponse(response))
}
private fun handleSearchForNewsResponse(response: Response<NewsResponse>) : Resource<NewsResponse>
{
if(response.isSuccessful)
response.body().let {
return Resource.Success(it)
}
else
return Resource.Error(response.message(), response.body())
}
/**Deal with Room**/
fun saveThisArticle(article: Article) = viewModelScope.launch {
repo.addIfNotExist(article)
/*Log.d("NewsViewModel "," => Start saving")
val num = repo.addIfNotExist(article).wait()
Log.d("NewsViewModel => saveThisArticle(article: Article) ", "--------- $num")*/
}
fun getMySavedArticles() = savedNews.postValue(repo.getSavedNews().value)
fun deleteThisArticle(article: Article) = viewModelScope.launch {
repo.deleteArticle(article)
}
class NewsVMFactory(val repo: NewsRepository) : ViewModelProvider.Factory {
override fun <T : ViewModel> create(modelClass: Class<T>): T {
if(modelClass.isAssignableFrom(NewsViewModel::class.java)){
#Suppress("UNCHECKED_CAST")
return NewsViewModel(repo) as T
}
throw IllegalArgumentException("Unknown viewModel class")
}
}
}
NewsRepository
class NewsRepository(val db: ArticleDatabase)
{
/**Remote**/
suspend fun getBreakingNews(country_of_2Letters : String, pageNum : Int) =
RetrofitInstance.newsAPI.getNewsHeadlines()
suspend fun getSearchedNews(text : String, pageNum : Int) =
RetrofitInstance.newsAPI.searchFor(text, pageNum)
/**Local**/
suspend fun addIfNotExist(article : Article) =
withContext(Dispatchers.IO) {
db.newsDatabaseDao.upsert(article)
}
fun getSavedNews() = db.newsDatabaseDao.getAllArticles()
suspend fun deleteArticle(article : Article) = db.newsDatabaseDao.deleteArticle(article)
}
interface NewsDao
#Dao
interface NewsDao {
#Insert(onConflict = OnConflictStrategy.REPLACE)
suspend fun upsert(article : Article): Long // TODO ???? Int
#Query("SELECT * FROM articles")
fun getAllArticles(): LiveData<List<Article>> // TODO There will be two tables. one for saved articles and other for cashing.
#Delete
suspend fun deleteArticle(article: Article)
}
ArticleDatabase
#Database(entities = [Article::class], version = 1, exportSchema = false)
#TypeConverters(Converters::class)
abstract class ArticleDatabase : RoomDatabase() {
abstract val newsDatabaseDao: NewsDao
companion object {
#Volatile
var INSTANCE: ArticleDatabase? = null
fun getInstance(context: Context): ArticleDatabase {
synchronized(this) {
return INSTANCE ?: Room.databaseBuilder(
context.applicationContext,
ArticleDatabase::class.java,
"article_database"
)
.fallbackToDestructiveMigration()
.build()
}
}
}
}
The model/data file
data class NewsResponse(
val articles: List<Article>,
val status: String, // ok
val totalResults: Int // 383
)
#Entity(tableName = "articles")
data class Article(
// #PrimaryKey(autoGenerate = true)
// val id : Int? = null, // tried: var, Int, Int = 0, Int?
#ColumnInfo(name = "author")
val author: String? = "",
#ColumnInfo(name = "content")
val content: String? = "",
#ColumnInfo(name = "description")
val description: String? = "",
#ColumnInfo(name = "published_at")
val publishedAt: String,
#ColumnInfo(name = "source")
val source: Source,
#ColumnInfo(name = "title")
val title: String,
#ColumnInfo(name = "url")
val url: String,
#ColumnInfo(name = "url_to_image")
val urlToImage: String?
) : Serializable
{
override fun hashCode(): Int {
var result = id.hashCode()
if(url.isNullOrEmpty()){
result = 31 * result + url.hashCode()
}
return result
}
}
data class Source(
val id: String, // business-insider
val name: String // The Guardian
)
Converters class
class Converters {
// data class Source(
// val id: String,
// val name: String
// )
#TypeConverter
fun fromSource(source: Source): String =
Gson().toJson(source) // set in the database as a string
#TypeConverter
fun toSource(stringSource: String) : Source =
Gson().fromJson(stringSource, Source::class.java) // get it from the database and compose it into its original datatype
}
ArticleFragment
class ArticleFragment : BaseFragment(R.layout.fragment_article) {
lateinit var binding : FragmentArticleBinding
val args : ArticleFragmentArgs by navArgs()
override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View {
binding = FragmentArticleBinding.inflate(inflater)
val data = args.anArticle
binding.webView.apply {
try{
webViewClient = WebViewClient()
loadUrl(data.url)
}
catch (e: Exception){
loadUrl("https://www.google.co.in/")
Toast.makeText(context, "There is a problem in the url", Toast.LENGTH_LONG).show()
}
}
binding.fab.setOnClickListener {
viewModel.saveThisArticle(data)
Toast.makeText(context, "Saved successfully ✅", Toast.LENGTH_SHORT).show()
}
return binding.root
}
override fun onDestroyView() {
super.onDestroyView()
binding.unbind()
}
}

How to convert a Flow<CustomType> to StateFlow<UIState>? - Android Kotlin

I am learning Android development, and as I saw in many topics, people were talking about that LiveData is not recommended to use anymore. I mean it's not up-to-date, and we should use Flows instead.
I am trying to get data from ROOM database with Flows and then convert them to StateFlow because as I know they are observables, and I also want to add UI states to them. Like when I get data successfully, state would change to Success or if it fails, it changes to Error.
I have a simple app for practicing. It stores subscribers with name and email, and show them in a recyclerview.
I've checked a lot of sites, how to use stateIn method, how to use StateFlows and Flows but didn't succeed. What's the most optimal way to do this?
And also what's the proper way of updating recyclerview adapter? Is it okay to change it all the time in MainActivity to a new adapter?
Here is the project (SubscriberViewModel.kt - line 30):
Project link
If I am doing other stuff wrong, please tell me, I want to learn. I appreciate any kind of help.
DAO:
import androidx.room.*
import kotlinx.coroutines.flow.Flow
#Dao
interface SubscriberDAO {
#Insert
suspend fun insertSubscriber(subscriber : Subscriber) : Long
#Update
suspend fun updateSubscriber(subscriber: Subscriber) : Int
#Delete
suspend fun deleteSubscriber(subscriber: Subscriber) : Int
#Query("DELETE FROM subscriber_data_table")
suspend fun deleteAll() : Int
#Query("SELECT * FROM subscriber_data_table")
fun getAllSubscribers() : Flow<List<Subscriber>>
#Query("SELECT * FROM subscriber_data_table WHERE :id=subscriber_id")
fun getSubscriberById(id : Int) : Flow<Subscriber>
}
ViewModel:
class SubscriberViewModel(private val repository: SubscriberRepository) : ViewModel() {
private var isUpdateOrDelete = false
private lateinit var subscriberToUpdateOrDelete: Subscriber
val inputName = MutableStateFlow("")
val inputEmail = MutableStateFlow("")
private val _isDataAvailable = MutableStateFlow(false)
val isDataAvailable : StateFlow<Boolean>
get() = _isDataAvailable
val saveOrUpdateButtonText = MutableStateFlow("Save")
val deleteOrDeleteAllButtonText = MutableStateFlow("Delete all")
/*
//TODO - How to implement this as StateFlow<SubscriberListUiState> ??
//private val _subscribers : MutableStateFlow<SubscriberListUiState>
//val subscribers : StateFlow<SubscriberListUiState>
get() = _subscribers
*/
private fun clearInput() {
inputName.value = ""
inputEmail.value = ""
isUpdateOrDelete = false
saveOrUpdateButtonText.value = "Save"
deleteOrDeleteAllButtonText.value = "Delete all"
}
fun initUpdateAndDelete(subscriber: Subscriber) {
inputName.value = subscriber.name
inputEmail.value = subscriber.email
isUpdateOrDelete = true
subscriberToUpdateOrDelete = subscriber
saveOrUpdateButtonText.value = "Update"
deleteOrDeleteAllButtonText.value = "Delete"
}
fun saveOrUpdate() {
if (isUpdateOrDelete) {
subscriberToUpdateOrDelete.name = inputName.value
subscriberToUpdateOrDelete.email = inputEmail.value
update(subscriberToUpdateOrDelete)
} else {
val name = inputName.value
val email = inputEmail.value
if (name.isNotBlank() && email.isNotBlank()) {
insert(Subscriber(0, name, email))
}
inputName.value = ""
inputEmail.value = ""
}
}
fun deleteOrDeleteAll() {
if (isUpdateOrDelete) {
delete(subscriberToUpdateOrDelete)
} else {
deleteAll()
}
}
private fun insert(subscriber: Subscriber) = viewModelScope.launch(Dispatchers.IO) {
repository.insert(subscriber)
_isDataAvailable.value = true
}
private fun update(subscriber: Subscriber) = viewModelScope.launch(Dispatchers.IO) {
repository.update(subscriber)
clearInput()
}
private fun delete(subscriber: Subscriber) = viewModelScope.launch(Dispatchers.IO) {
repository.delete(subscriber)
clearInput()
}
private fun deleteAll() = viewModelScope.launch(Dispatchers.IO) {
repository.deleteAll()
//_subscribers.value = SubscriberListUiState.Success(emptyList())
_isDataAvailable.value = false
}
sealed class SubscriberListUiState {
data class Success(val list : List<Subscriber>) : SubscriberListUiState()
data class Error(val msg : String) : SubscriberListUiState()
}
}
MainActivity:
class MainActivity : AppCompatActivity() {
private lateinit var binding: ActivityMainBinding
private lateinit var viewModel: SubscriberViewModel
private lateinit var viewModelFactory: SubscriberViewModelFactory
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
binding = DataBindingUtil.setContentView(this, R.layout.activity_main)
val dao = SubscriberDatabase.getInstance(application).subscriberDAO
viewModelFactory = SubscriberViewModelFactory(SubscriberRepository(dao))
viewModel = ViewModelProvider(this, viewModelFactory)[SubscriberViewModel::class.java]
binding.viewModel = viewModel
binding.lifecycleOwner = this
initRecycleView()
}
private fun initRecycleView() {
binding.recyclerViewSubscribers.layoutManager = LinearLayoutManager(
this#MainActivity,
LinearLayoutManager.VERTICAL, false
)
displaySubscribersList()
}
private fun displaySubscribersList() {
/*
lifecycleScope.launch {
repeatOnLifecycle(Lifecycle.State.STARTED) {
viewModel.subscribers.collect { uiState ->
when (uiState) {
is SubscriberViewModel.SubscriberListUiState.Success -> {
binding.recyclerViewSubscribers.adapter = SubscriberRecyclerViewAdapter(uiState.list) {
subscriber: Subscriber -> listItemClicked(subscriber)
}
}
is SubscriberViewModel.SubscriberListUiState.Error -> {
Toast.makeText(applicationContext,uiState.msg, Toast.LENGTH_LONG).show()
}
}
}
}
}*/
}
private fun listItemClicked(subscriber: Subscriber) {
Toast.makeText(this, "${subscriber.name} is selected", Toast.LENGTH_SHORT).show()
viewModel.initUpdateAndDelete(subscriber)
}
}

You can convert a Flow type into a StateFlow by using stateIn method.
private val coroutineScope = CoroutineScope(Job())
private val flow: Flow<CustomType>
val stateFlow = flow.stateIn(scope = coroutineScope)
In order to transform the CustomType into UIState, you can use the transformLatest method on Flow. It will be something like below:
stateFlow.transformLatest { customType ->
customType.toUiState()
}
Where you can create an extension function to convert CustomType to UiState like this:
fun CustomType.toUiState() = UiState(
x = x,
y = y... and so on.
)

How can i get one item from Room database?

So, I have two ViewModels and two screens in my app. The first screen is for the presentation of a list of diary item elements, second is for detailed information on diary items. In a second ViewModel, I have an id to get a record from DB but can find it. What can I do to get it?
DAO:
interface DiaryDao {
#Query("SELECT * FROM diaryItems")
fun getAllDiaryPosts(): LiveData<List<DiaryItem>>
#Query("Select * from diaryItems where id = :id")
fun getDiaryPostById(id: Int) : DiaryItem
#Query("Delete from diaryItems where id = :index")
fun deleteDiaryPostByIndex(index : Int)
#Insert(onConflict = OnConflictStrategy.REPLACE)
suspend fun insertDiaryPost(diaryItem: DiaryItem)
#Update
suspend fun updateDiaryPost(diaryItem: DiaryItem)
#Delete
suspend fun deleteDiaryPost(diaryItem: DiaryItem)
#Query("Delete from diaryItems")
suspend fun deleteAllDiaryItems()
}
Repository
class DiaryRepository #Inject constructor(private val diaryDao: DiaryDao) {
val readAllData: LiveData<List<DiaryItem>> = diaryDao.getAllDiaryPosts()
suspend fun getDiaryPostDyIndex(index: Int): DiaryItem {
return diaryDao.getDiaryPostById(index)
}
}
First viewmodel
#HiltViewModel
class PostListViewModel
#Inject
constructor(
private val diaryRepository: DiaryRepository,
) : ViewModel() {
private var allDiaryItems: LiveData<List<DiaryItem>> = diaryRepository.readAllData
}
Second viewmodel
#HiltViewModel
class PostDetailViewModel
#Inject
constructor(
private val savedStateHandle: SavedStateHandle,
private val diaryRepository: DiaryRepository
) : ViewModel() {
sealed class UIState {
object Loading: UIState()
data class Success(val currentPosts: DiaryItem) : UIState()
object Error : UIState()
}
val postDetailState: State<UIState>
get() = _postDetailState
private val _postDetailState = mutableStateOf<UIState>(UIState.Loading)
init {
viewModelScope.launch (Dispatchers.IO) {
try {
val diaryList: DiaryItem = diaryRepository.getDiaryPostDyIndex(2) //it is for test
_postDetailState.value = UIState.Success(diaryList)
} catch (e: Exception) {
withContext(Dispatchers.Main) {
_postDetailState.value = UIState.Error
}
}
}
}
}

I am sure you are getting errors. because you updating UI State in IO Thread
fun getDairyItem(itemId: Int){
viewModelScope.launch (Dispatchers.IO) {
try {
val diaryList: DiaryItem = diaryRepository.getDiaryPostDyIndex(itemId)
withContext(Dispatchers.Main) {
_postDetailState.value = UIState.Success(diaryList)
}
} catch (e: Exception) {
withContext(Dispatchers.Main) {
_postDetailState.value = UIState.Error
}
}
}
}

Implementing Room with a viewmodel,how to get the return value of a query in DAO. instead of a List<> it just returns "CouroutineJob"

i am implementing Room with a vIewModel, my structure is the following
#DAO,#Entity,#Database,#Repository
#Entity(tableName="dx_table")
class dx_table(
#ColumnInfo(name = "name")
val naxme: String,
#PrimaryKey
#ColumnInfo(name = "phone")
val phone: String,
#ColumnInfo(name = "passx")
val passx: String,
#ColumnInfo(name = "login_fx")
val login_fx: String
)
#Dao
interface dx_dao{
#Query("SELECT * FROM dx_table")
fun get_all():LiveData<List<dx_table>>
#Insert
suspend fun insertTrx(dx_table:dx_table)
#Query("UPDATE dx_table SET login_fx =:login_fx where phone=:phonex")
suspend fun insertFx(login_fx: String,phonex: String)
#Query("SELECT * from dx_table where phone=:phonex")
suspend fun get_name_px(phonex: String):List<dx_table>
#Query("Delete from dx_table")
suspend fun deleteAll()
#Query("Select * from dx_table where login_fx=1")
suspend fun selectFx():List<dx_table>
}
#Database(entities = arrayOf(dx_table::class), version = 1, exportSchema = false)
public abstract class DxDatabase : RoomDatabase() {
abstract fun dxDao(): dx_dao
companion object {
// Singleton prevents multiple instances of database opening at the
// same time.
#Volatile
private var INSTANCE: DxDatabase? = null
fun getDatabase(context: Context): DxDatabase {
val tempInstance = INSTANCE
if (tempInstance != null) {
return tempInstance
}
synchronized(this) {
val instance = Room.databaseBuilder(
context.applicationContext,
DxDatabase::class.java,
"dx_database"
).build()
INSTANCE = instance
return instance
}
}
}
}
class dxRepository(private val dxDao: dx_dao ){
val k_d:LiveData<List<dx_table>> = dxDao.get_all()
suspend fun insert_trx(dx_table: dx_table){
dxDao.insertTrx(dx_table)
}
suspend fun insert_fx(login_fx: String,phonex: String) {
dxDao.insertFx(login_fx,phonex)
}
suspend fun select_fx() {
dxDao.selectFx()
}
suspend fun get_name_px(phonex: String) :List<dx_table> {
return dxDao.get_name_px(phonex) as List<dx_table>
}
}
The viewmodel is
class DxViewModel (application: Application) : AndroidViewModel(application) {
var repository: dxRepository
var k_d: LiveData<List<dx_table>>
init {
// Gets reference to WordDao from WordRoomDatabase to construct
// the correct WordRepository.
val dxDao = DxDatabase.getDatabase(application).dxDao()
repository = dxRepository(dxDao)
k_d = repository.k_d
}
fun insert_trx(dxTable: dx_table) = viewModelScope.launch {
repository.insert_trx(dxTable)
}
fun insert_fx(login_fx: String, phonex: String) = viewModelScope.launch {
repository.insert_fx(login_fx, phonex)
}
fun select_fx() = viewModelScope.launch {
repository.select_fx()
}
fun get_name_px(phonex: String) = viewModelScope.launch {
repository.get_name_px(phonex)
}
}
I can track the live data using observe,its not an issue, the problem i am facing is with the get_name_px(phone)
var mView = ViewModelProviders.of(this).get(DxViewModel::class.java)
var lm = mView.get_name_px(phone)
here lm seems to be job type , i need the return List , how do i get it .

In your viewModel function select_fx() return a job, because launch does not return result, so you have to either:
1) Use async and await
fun get_name_px(phonex: String) = viewModelScope.async {
repository.get_name_px(phonex)
}.await()
2) Not use launch viewModel, use it in Activity/Fragment
suspend fun get_name_px(phonex: String) = repository.get_name_px(phonex)
class CardFragment : Fragment() {
fun get() {
// launch in Dispatchers.Main
lifecycleScope.launch {
var lm = mView.get_name_px(phone)
}
// launch in background thread
lifecycleScope.launch(Dispatchers.Default) {
var lm = mView.get_name_px(phone)
}
}
}

Send a parameter to Kotlin retrofit call

I am a beginner in Kotlin. I need to send a variable parameter from my Activity to a Retrofit call.
This is my call in on Create of Detail Activity
override fun onCreate(savedInstanceState: Bundle?) {
//...
val id = intent.getStringExtra("id")
// Get the ViewMode
val mModel = ViewModelProviders.of(this).get(myObjectViewModel::class.java)
//Create the observer which updates the UI.
val myObjectByIdObserver = Observer<MyObject> { myObject->
//...
}
//Observe the LiveData, passing in this activity as the LifecycleOwner and the observer.
mModel.getObjectById.observe(this, myObjectByIdObserver)
}
Here I insert value hardcode, I need the parameter received from the previous Activity.
class MyObjectViewModel : ViewModel() {
//this is the data that we will fetch asynchronously
var myObject: MutableLiveData<MyObject>? = null
val getMyObjectById: LiveData<MyObject>
get() {
if (myObject == null) {
myObject = MutableLiveData()
loadMyObjectById()
}
return myObject as MutableLiveData<MyObject>
}
private fun loadMyObjectById() {
val retrofit = Retrofit.Builder()
.baseUrl(Api.BASE_URL)
.addConverterFactory(GsonConverterFactory.create())
.build()
val api = retrofit.create(Api::class.java)
val call = api.myObjectById(100)
call.enqueue(object : Callback<MyObject> {
override fun onResponse(call: Call<MyObject>, response: Response<MyObject>) {
myObject!!.value = response.body()
}
override fun onFailure(call: Call<MyObject>, t: Throwable) {
var tt = t
}
})
}
My API:
interface Api {
companion object {
const val BASE_URL = "https://.../"
}
#GET("myObjects/{id}")
fun myObjectById(#Path("id") id: Int?): Call<MyObject>
}

You can do this by ``#Query``` annotation.
interface Api {
companion object {
const val BASE_URL = "https://.../"
}
#GET("myObjects/{id}")
fun myObjectById(#Path("id") id: Int?, #Query("a_param") aParam: String?): Call<MyObject>
}
Edited. I completely misread your intension.
What you need seems to be ViewModelProvider.NewInstanceFactory like
class MyObjectViewModel(val id: Int): ViewModel() {
class Factory(val id: Int) : ViewModelProvider.NewInstanceFactory() {
override fun <T : ViewModel?> create(modelClass: Class<T>): T {
return MyObjectViewModel(id) as T
}
}
}
then
val myViewModel = ViewModelProviders
.of(this, MyObjectViewModel.Factory(id))
.get(MyObjectViewModel::class.java)