I am using the latest Koin version 3.1.2. I have a basic Fragment that accepts a String parameter to it's constructor.
My Koin setup is as follows:
Activity:
override val scope: Scope by activityScope()
private val fragment by inject<MyFragment> {
parametersOf(intent.getStringExtra(PROJECT_ID_EXTRA))
}
override fun onCreate(savedInstanceState: Bundle?) {
setupKoinFragmentFactory(scope)
super.onCreate(savedInstanceState)
.
.
}
Fragment:
class MyFragment(private val projectId: String?) : BaseFragment() {
}
Koin Module:
scope<MyActivity> {
fragment { (projectId: String) -> MyFragment(projectId) }
}
To simulate activity re-creation, I have turned on Don't keep activities flag in the developer options.
What always happens when activity is re-created, I get the following exception:
Unable to start activity ComponentInfo{com.activity.MyActivity}: org.koin.core.error.InstanceCreationException: Could not create instance for [Factory:'com.fragment.MyFragment',scope:q:'com.activity.MyActivity']
Can't get injected parameter #0 from DefinitionParameters[] for type 'java.lang.String'
Related
i'am using retrofit library to get info from internet api , then i put the data in the repository then get it in viewmodel which it will be instatiate by viewmodelfactory ;
so i'am trying to inject HitViewModelFactory by using Dagger-Hilt in Fragment but it show me an error when to inject it in the fragment
lateinit property hitViewModelFactory has not been initialized
i make an application class and anotate it with #HiltAndroidApp and give the name of application in manifest. and make anotate to activity that host this fragment but the problem not solved
#AndroidEntryPoint
class BaseActivity : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
.......
}
}
i provide all dependencies that i need in the module class :
#Module
#InstallIn(ApplicationComponent::class)
object AppModule {
#Singleton
#Provides
fun provideHitPhotoApi() = Retrofit.Builder()
.baseUrl(BASE_URL)
.addConverterFactory(GsonConverterFactory.create())
.build()
.create(HitApi::class.java)
#Singleton
#Provides
fun provideHitRepository(hitApi: HitApi) = HitRepository(hitApi)
#Singleton
#Provides
fun provideHitViewModelFactory(hitRepository: HitRepository) : HitViewModelFactory = HitViewModelFactory(hitRepository)
}
and try to inject ViewModelFactory in this fragment
#AndroidEntryPoint
class TripsFragment : Fragment() {
#Inject
lateinit var hitViewModelFactory: HitViewModelFactory
lateinit var hitViewModel: HitViewModel
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
hitViewModel = ViewModelProvider(requireActivity(),hitViewModelFactory)[HitViewModel::class.java ]
}
dependency for hilt :
Dagger - Hilt
implementation "com.google.dagger:hilt-android:2.28-alpha"
kapt "com.google.dagger:hilt-android-compiler:2.28-alpha"
implementation "androidx.hilt:hilt-lifecycle-viewmodel:1.0.0-
alpha03"
kapt "androidx.hilt:hilt-compiler:1.0.0"
I also faced same issue earlier. Not sure why this fails but it seems code is correct.
So I have done with different approach.
I created view model like this below. And I inject HitApi directly in viewmodel constructor. Then just initialize like below. It takes care of creating viewmodel instance and hilt takes care of injection.No need of creating factory.
ViewModel:
#HiltViewModel
class HitViewModel #Inject constructor(
var api: HitApi) : ViewModel() {
}
Fragment:
#AndroidEntryPoint
class TripsFragment : Fragment() {
private val viewModel by viewModels<HitViewModel>() //No need of inject annotation.
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
}
}
Make sure you have these dependancies.
//For activity
implementation 'androidx.activity:activity-ktx:1.5.1'
//For fragment
implementation 'androidx.fragment:fragment-ktx:1.5.1'
the problem solved when i change the dependency of Hilt to :
implementation "com.google.dagger:hilt-android:2.38.1"
kapt "com.google.dagger:hilt-compiler:2.38.1"
implementation "androidx.hilt:hilt-lifecycle-viewmodel:1.0.0-alpha03"
kapt "androidx.hilt:hilt-compiler:1.0.0"
and for these dependencies it should replace the InstallIn anotation for module class to SingletonComponent::class like
#Module
#InstallIn(SingletonComponent::class)
object AppModule { ... }
I'm trying to instanciate a Room database in my main activity in Android Studio, following codelabs and tutorials, but my app always crash. Here's a part of the code:
My database (AppDatabase.kt):
#Database(entities = [Device::class], version = 1, exportSchema = false)
abstract class AppDatabase : RoomDatabase() {
abstract fun deviceDao(): DeviceDao
companion object {
#Volatile
private var INSTANCE: AppDatabase? = null
fun getDatabase(context: Context): AppDatabase {
return INSTANCE ?: synchronized(this) {
val instance = Room.databaseBuilder(
context.applicationContext,
AppDatabase::class.java,
"item_database"
)
.fallbackToDestructiveMigration()
.build() // <---- The crash occurs here
INSTANCE = instance
return instance
}
}
}
}
And here's the activity from which I'm trying to instantiate it:
class NavigationActivity() : AppCompatActivity() {
private lateinit var binding: ActivityNavigationBinding
private val db by lazy { AppDatabase.getDatabase(this) }
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
binding = ActivityNavigationBinding.inflate(layoutInflater)
setContentView(binding.root)
Log.d("instantiation", "$db") // <----- Called from here
val navView: BottomNavigationView = binding.navView
val navController = findNavController(R.id.nav_host_fragment_activity_navigation)
val appBarConfiguration = AppBarConfiguration(
setOf(
R.id.navigation_devices, R.id.navigation_logs, R.id.navigation_settings
)
)
setupActionBarWithNavController(navController, appBarConfiguration)
navView.setupWithNavController(navController)
}
}
Finally, here's the error message, which doesn't helps me much:
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String java.lang.Package.getName()' on a null object reference
at androidx.room.Room.getGeneratedImplementation(Room.java:82)
at androidx.room.RoomDatabase$Builder.build(RoomDatabase.java:1486)
at AppDatabase$Companion.getDatabase(AppDatabase.kt:24)
I tried a lot of things, including ViewModel, Repository and more, but got the crash systematically, at the same point.
Here's also the part of my build.gradle file where I import Room, maybe I'm wrong in some version or whatever...
plugins {
id 'com.android.application'
id 'org.jetbrains.kotlin.android'
id 'kotlin-android'
id 'kotlin-kapt'
}
[...]
def roomVersion = "2.4.2"
implementation("androidx.room:room-runtime:$roomVersion")
kapt("androidx.room:room-compiler:$roomVersion")
implementation "androidx.room:room-ktx:$roomVersion"
Make sure package declaration on top of the class is declared, for example:
package com.macrosystems.clean.ui.core.view
import android.content.Context
import android.content.Intent
import android.graphics.Color
etc...
I can run Code A in Android Studio, I hope to preview UI when I'm designing, so I added Code B to Code A.
But Code B can't work, why? How can I fix it?
Code A
class MainActivity : ComponentActivity() {
private val handleMeter by viewModels<HandleMeter>()
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContent {
SoundMeterTheme {
Surface(color = MaterialTheme.colors.background) {
Greeting(handleMeter)
}
}
}
}
}
#Composable
fun Greeting(handleMeter: HandleMeter) {
...
}
Code B
#Preview(showBackground = true)
#Composable
fun DefaultPreview() {
SoundMeterTheme {
val handleMeter by viewModels<HandleMeter>()
Greeting(handleMeter)
}
}
Unfortunately, you can't.
Preview does not support creating ViewModels and NavHost yet, for our bad.
But what you can do instead is to use a fake data or a static data into ui, until the design finish and when you are ready to actually run it, replace the static data with the view model data.
You can use dagger and hilt to inject the view model constructor and then call up the hilt view model in the preview e.g.
#HiltViewModel
class DataFieldsViewModel #Inject constructor(
) : ViewModel() {
Then in your preview code for your composable
#Preview(showBackground = true)
#Composable
fun PreviewDataFieldsScreen() {
DataFieldsScreen(
navController = rememberNavController(),
viewModel = hiltViewModel()
)
}
I am struggling to use Live data on an MVVM pattern. The app is supposed to:
Fetch data from an API (which it does correctly)
Store that data in the Live data object from the ViewModel
Then the fragment calls the Observer method to fill the recyclerView.
The problem comes in point 3, it does nothing, and I cannot find the solution.
Here is the relevant code. (If I'm missing something, I will try to answer as quickly as possible)
Main Activity:
class MainActivity : AppCompatActivity() {
private lateinit var binding: ActivityMainBinding
private val viewModel: SharedViewModel by viewModels()
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
binding = ActivityMainBinding.inflate(layoutInflater)
setContentView(binding.root)
// Custom button to fetch data from api and log the Live Data value.
binding.refreshFab.setOnClickListener {
viewModel.fetchPlayerData()
Log.d("gabs", "${viewModel.livePlayerlist.value}")
}
}
}
ViewModel:
class SharedViewModel(app: Application): AndroidViewModel(app) {
// val playerDao = LaRojaDB.getDatabase(app).playerDao()
lateinit var playerList: Players
val livePlayerlist: MutableLiveData<MutableList<Players.PlayersItem>> by lazy {
MutableLiveData<MutableList<Players.PlayersItem>>()
}
fun fetchPlayerData() {
CoroutineScope(Dispatchers.IO).launch {
val response = MyService.getLaRojaService().getAllPlayers()
withContext(Dispatchers.Main) {
if (response.isSuccessful) {
val body = response.body()
if(!body.isNullOrEmpty()){
playerList = body
val playerArrayList = mutableListOf<Players.PlayersItem>()
playerList.forEach {
playerArrayList.add(it)
}
livePlayerlist.value = playerList
}
}
}
}
}
}
The fragment that displays the recycler view: (Fragment is already showing, I set up a textView as a title to make sure since I'm new using fragments as well.)
class PlayerListFragment : Fragment() {
private var _binding: FragmentPlayerListBinding? = null
private val binding get() = _binding!!
private val model: SharedViewModel by viewModels()
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
_binding = FragmentPlayerListBinding.inflate(inflater, container, false)
binding.rvPlayerList.layoutManager = LinearLayoutManager(activity)
----> // This is the observer that does not update the UI** <----
model.livePlayerlist.observe( viewLifecycleOwner, {
binding.rvPlayerList.adapter = PlayerAdapter(it)
})
// Inflate the layout for this fragment
return inflater.inflate(R.layout.fragment_player_list, container, false)
}
}
Thank you all in advance, hope I can finally learn what is causing the issue!
I think you don't need to switch Coroutine contexts. A few changes I'd expect if I were reviewing this code:
This should all be in the same IO context. You then postValue to your liveData.
fun fetchPlayerData() {
viewModelScope.launch(Dispatchers.IO) {
val xx = api.fetch()
...
_playerState.postValue(xx) //see below
}
}
Additionally, it's preferred not to expose mutable state, so your ViewModel should not expose the MutableLiveData (which shouldn't really be lazy). But it's also better to encapsulate the state in a sealed class:
//delete this
val livePlayerlist: MutableLiveData<MutableList<Players.PlayersItem>> by lazy {
MutableLiveData<MutableList<Players.PlayersItem>>()
}
Should be: (names are just pseudo code, I have no idea what this code is about)
sealed class PlayerDataState {
data class ListAvailable(data: List<Players.PlayersItem>>): PlayerDataState
object Loading(): PlayerDataState
}
And your new LiveData:
private val _playerState = MutableLiveData<PlayerDataState>()
val playerState: LiveData<PlayerDataState>() get() = _playerState
Finally when observing from the UI, you just...
model.playerState.observe(viewLifecycleOwner, {
when (it) {
is Loading -> ...
is ListAvailable -> binding.rvPlayerList.adapter = PlayerAdapter(it.data)
}
}
I'm using the Realm database in my kotlin project.
I use MVVM architecture so I created a repository class which contains codes bellow:
class DatabaseRepository {
private val database = Realm.getDefaultInstance()
fun addOrUpdateUser(user: JSONObject) {
database.executeTransactionAsync{
database.createOrUpdateObjectFromJson(UserModel::class.java, user)
}
}
}
also, I have created my ViewModel class like this:
class DatabaseViewModel(private val database:DatabaseRepository) : ViewModel() {
fun addUser(information: JSONObject) {
database.addOrUpdateUser(information)
}
}
and my View ModelFactory class is like this:
class ViewModelFactory(private val databaseRepository:DatabaseRepository):ViewModelProvider.Factory {
override fun <T : ViewModel?> create(modelClass: Class<T>): T {
return modelClass.getConstructor(DatabaseRepository::class.java).newInstance(databaseRepository)
}
}
so I create the instance of them in my MainActivity like this:
val databaseRepo=DatabaseRepository()
val factory=ViewModelFactory(databaseRepo)
database = ViewModelProviders.of(this,factory).get(DatabaseViewModel::class.java)
the problem is that while I'm trying to add some data to Database using 'addUser' function in ViewModel class I get this error:
Realm objects can only be accessed on the thread they were created.
what have I done wrong?
the only problem was because of executeTransactionAsync, so I changed from:
executeTransactionAsync
to
executeTransaction
and it worked!