I have made a simple app that tells the car is a two-wheeler or four-wheeler with the help of dagger2 but an error will occur if I run the app and the error is binding is missing for this I have also used #Named annotation but the error is coming again and again.
MainActivity.kt
class MainActivity : AppCompatActivity() {
#Inject
lateinit var car: Car
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
DaggerCarComp.builder().build().inject(this)
car.tellCarTypes()
}
}
Car.kt
class Car #Inject constructor(
#Named("two") val tw: TW,
val fw: FW
) {
fun tellCarTypes() {
tw.whichCar()
}
}
CarComp.kt
#Component(modules = [CarModule::class])
interface CarComp {
fun inject (mainActivity: MainActivity)
}
CarType.kt
interface CarType {
fun whichCar()
}
class TW #Inject constructor() : CarType {
override fun whichCar() {
Log.d("Type", "whichCar: Two wheeler")
}
}
class FW : CarType {
override fun whichCar() {
Log.d("Type", "whichCar: Four wheeler")
}
}
CarModule.kt
#Module
class CarModule {
#Provides
#Named("two")
fun tellCar(tw: TW) : CarType {
return tw
}
#Provides
#Named("four")
fun tellCar2() : CarType {
return FW()
}
}
Error image
Your class FW does not have the #Inject annotation alongside his constructor. I think it has to be defined this way so Dagger know what to do
class FW #Inject constructor() : CarType {
override fun whichCar() {
Log.d("Type", "whichCar: Four wheeler")
}
}
Also your function tellCar2 should probably be defined in this way :
#Provides
#Named("four"
fun tellCar2(fw: FW) : CartType {
return fw
}
Since you are using an interface, you could also use #Binds in an abstract module and so you can directly bind the correct implementation of the interface regarding your needs. Check this article : https://medium.com/mobile-app-development-publication/dagger-2-binds-vs-provides-cbf3c10511b5 or this : https://dagger.dev/api/2.21/dagger/Binds.html
Related
I am currently learning how to inject into Android apps with Dagger 2. I wrote a very basic code, but it refuses to work. My goals is it to inject the MainActicity as it should be. It builds
My code:
class MainActivity : AppCompatActivity() {
#Inject lateinit var info: Info
override fun onCreate(savedInstanceState: Bundle?) {
AndroidInjection.inject(this)
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
txt_view.text = info.textInformation
}
}
class Info {val textInformation = "You are able to read this" }
#Module
class InfoModule{
#Provides
fun info ():Info{
return Info()
}
}
class CustomApp : Application (),HasActivityInjector{
#Inject
lateinit var dispatchingAndroidInjector: DispatchingAndroidInjector<Activity>
override fun activityInjector(): AndroidInjector<Activity> {
return dispatchingAndroidInjector
}
}
#Component(modules = arrayOf(AndroidInjectionModule::class,
ActivityModule::class))
interface ApplicationComponent{
fun inject(application: CustomApp)
}
#Module
abstract class ActivityModule{
#ContributesAndroidInjector(modules = arrayOf(InfoModule::class))
abstract fun contributeInfoActivityInjector():MainActivity
}
The answer is that I forgot to add this code to the CustomApp class, and .CustomApp to the manifest file
override fun onCreate() {
super.onCreate()
initDi()
}
private fun initDi() {
DaggerApplicationComponent.builder().build().inject(this)
}
I try to learn how to use Dagger 2. Please help with follow exception:
Exception:
UninitializedPropertyAccessException: lateinit property trips has not
been initialized
MainActivityViewModel:
class MainActivityViewModel : ViewModel() {
private lateinit var tripsLiveData: MutableLiveData<List<Trip>>
#Inject
lateinit var trips : List<Trip>
fun getTrips() : LiveData<List<Trip>> {
if (!::tripsLiveData.isInitialized){
tripsLiveData = MutableLiveData()
tripsLiveData.value = trips
}
return tripsLiveData
}
}
TripModule:
#Module
class TripModule{
#Provides
fun provideTrips(): List<Trip> {
var list = ArrayList<Trip>()
list.add(Trip(100,10))
list.add(Trip(200,20))
return list
}
}
AppComponent:
#Singleton
#Component(modules = [
AndroidSupportInjectionModule::class,
ActivityBuilder::class,
TripModule::class])
interface AppComponent{
#Component.Builder
interface Builder {
#BindsInstance
fun application(application: Application): Builder
fun build(): AppComponent
}
fun inject(app: MyApplication)
}
MainActivity:
class MainActivity : AppCompatActivity() {
#Inject
lateinit var tripsAdapter: TripsAdapter
override fun onCreate(savedInstanceState: Bundle?) {
// Inject external dependencies
AndroidInjection.inject(this)
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
setupRecyclerView();
setUpViewModel();
}
private fun setupRecyclerView() {
recycler_view.apply {
layoutManager = LinearLayoutManager(context)
adapter = tripsAdapter
}
}
private fun setUpViewModel(){
val model = ViewModelProviders.of(this).get(MainActivityViewModel::class.java)
model.getTrips().observe(this, Observer { tripsAdapter.trips = it!! })
}
}
If you want your viewmodel's to be part of the dagger graph, you need to do several things - using dagger's multibindings (just once, for newer viewmodels it will be easier). You'd create new viewmodel factory which will take care of instantiating viewmodels. This factory will be part of dagger graph and therefore will have references to anything provided via dagger. You can then have either constructor injection via #Inject constructor(anyParameterFromDagger: Param) or #Inject lateinit var someParam: Param inside the body of viewmodel.
1) Create qualifier for view model classes
#MustBeDocumented
#Target(AnnotationTarget.FUNCTION)
#Retention(AnnotationRetention.RUNTIME)
#MapKey
annotation class ViewModelKey(val value: KClass<out ViewModel>)
2) create viewmodel factory which takes values from dagger's multibindings
#Singleton
class DaggerViewModelFactory #Inject constructor(
private val creators: Map<Class<out ViewModel>, #JvmSuppressWildcards Provider<ViewModel>>
) : ViewModelProvider.Factory {
#Suppress("UNCHECKED_CAST")
override fun <T : ViewModel> create(modelClass: Class<T>): T {
var creator: Provider<out ViewModel>? = creators[modelClass]
if (creator == null) {
for ((key, value) in creators) {
if (modelClass.isAssignableFrom(key)) {
creator = value
break
}
}
}
if (creator == null) {
throw IllegalArgumentException("unknown model class $modelClass")
}
try {
return creator.get() as T
} catch (e: Exception) {
throw RuntimeException(e)
}
}
}
3) have dagger module which will provide the factory (from point 2) and then your viewmodels
abstract class YourDaggerModuleWhichThenNeedToBePartOfYourGraphAsIncluded {
#Binds
abstract fun bindViewModelFactory(factory: DaggerViewModelFactory): ViewModelProvider.Factory // this needs to be only one for whole app (therefore marked as `#Singleton`)
#Binds
#IntoMap
#ViewModelKey(MainActivityViewModel::class)
abstract fun bindMainActivityViewModel(vm: MainActivityViewModel): ViewModel // for every viewmodel you have in your app, you need to bind them to dagger
}
4) in your activity, when you get your viewmodel, you need to use the factory from dagger: (places changed marked as // TODO in the code below)
class MainActivity : AppCompatActivity() {
#Inject
lateinit var tripsAdapter: TripsAdapter
#Inject
lateinit var viewModelFactory: ViewModelProvider.Factory // TODO this was added to the activity
override fun onCreate(savedInstanceState: Bundle?) {
// Inject external dependencies
AndroidInjection.inject(this)
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
setupRecyclerView();
setUpViewModel();
}
private fun setupRecyclerView() {
recycler_view.apply {
layoutManager = LinearLayoutManager(context)
adapter = tripsAdapter
}
}
private fun setUpViewModel(){
val model = ViewModelProviders.of(this, viewModelFactory)[MainActivityViewModel::class.java] // TODO this was changed
model.getTrips().observe(this, Observer { tripsAdapter.trips = it!! })
}
}
I didn't provide the code for including module to dagger component as I hope this is something you already did.
You can read more about this e.g. in this medium article (I'm not author of the article):
#Provides
fun provideTrips(): List<Trip> {
I'm a bit wary of this in the sense that I doubt that it's really Dagger's job to provide this for you directly, but I'll just take that for granted and ignore that for now.
Your code should be:
class MainActivityViewModel #Inject constructor(
trips: List<Trip>
): ViewModel() {
private val tripsLiveData: MutableLiveData<List<Trip>> = MutableLiveData()
init {
tripsLiveData.setValue(trips)
}
fun getTrips() : LiveData<List<Trip>> = tripsLiveData
}
#Module
class TripModule{
#Provides
// #Singleton // <-- possibly should be here?
fun provideTrips(): List<Trip> = listOf(
Trip(100,10),
Trip(200,20)
)
}
#Singleton
#Component(modules = [
AndroidSupportInjectionModule::class,
ActivityBuilder::class,
TripModule::class
])
interface AppComponent{
#Component.Builder
interface Builder {
#BindsInstance
fun application(application: Application): Builder
fun build(): AppComponent
}
fun inject(app: MyApplication)
}
class MainActivity : AppCompatActivity() {
#Inject
lateinit var viewModelProvider: Provider<MainActivityViewModel>
// this is specifically not marked with `#Inject`
lateinit var viewModel: MainActivityViewModel
private val tripsAdapter = TripsAdapter()
override fun onCreate(savedInstanceState: Bundle?) {
// Inject external dependencies
AndroidInjection.inject(this)
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
setupRecyclerView();
setUpViewModel();
}
private fun setupRecyclerView() {
recycler_view.apply {
layoutManager = LinearLayoutManager(context)
adapter = tripsAdapter
}
}
private fun setUpViewModel(){
viewModel = ViewModelProviders.of(this, object: ViewModelProvider.Factory {
override fun <T : ViewModel?> create(modelClass: Class<T>): T {
if(modelClass == MainActivityViewModel::class.java) {
#Suppress("UNCHECKED_CAST")
return viewModelProvider.get() as T
}
throw IllegalArgumentException("Unexpected argument: $modelClass")
}
}).get(MainActivityViewModel::class.java)
viewModel.getTrips().observe(this, Observer {
val trips = it ?: return#observe
tripsAdapter.trips = trips
})
}
}
Aka you should use constructor injection, use the Provider<T> to only get the ViewModel from Dagger when you actually need it, and otherwise initialize it via a ViewModelProviders.Factory so that you actually get the ViewModel from Dagger.
I am new to unit testing in Android and have gone through several tutorials to get myself familiar with mockito and robolectric.
My app is using Dagger 2 to inject my EventService into my MainActivity. For my MainActivityUnitTest, I have set up a TestServicesModule to provide a mocked version of EventService so that I can use Robolectric to run unit tests against my MainActivity
I'm having an issue getting the ServiceCallback on my EventService.getAllEvents(callback: ServiceCallback) to execute in the unit test. I have verified in the #Setup of my MainActivityUnitTest class that the EventService is being injected as a mocked object. I have gone through several tutorials and blog posts and as far as I can tell, I am doing everything correctly. The refreshData() function in MainActivity is getting called successfully, and I can see that the call to eventsService.getAllEvents(callback) is being executed. But the doAnswer {} lambda function is never getting executed.
Here's my relevant code:
AppComponent.kt
#Singleton
#Component(modules = [
AppModule::class,
ServicesModule::class,
FirebaseModule::class
])
interface AppComponent {
fun inject(target: MainActivity)
}
ServicesModule.kt
#Module
open class ServicesModule {
#Provides
#Singleton
open fun provideEventService(db: FirebaseFirestore): EventsService {
return EventsServiceImpl(db)
}
}
EventsService.kt
interface EventsService {
fun getAllEvents(callback: ServiceCallback<List<Event>>)
fun getEvent(id: String, callback: ServiceCallback<Event?>)
}
MainActivity.kt
class MainActivity : AppCompatActivity() {
#Inject lateinit var eventsService: EventsService
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
(application as App).appComponent.inject(this)
...
}
override fun onStart() {
super.onStart()
refreshData()
}
eventsService.getAllEvents(object: ServiceCallback<List<Event>> {
override fun onCompletion(result: List<Event>) {
viewModel.allEvents.value = result
loading_progress.hide()
}
})
}
Now we get into the tests:
TestAppComponent.kt
#Singleton
#Component(modules = [
TestServicesModule::class
])
interface TestAppComponent : AppComponent {
fun inject(target: MainActivityUnitTest)
}
TestServicesModule.kt
#Module
class TestServicesModule {
#Provides
#Singleton
fun provideEventsService(): EventsService {
return mock()
}
}
MainActivityUnitTest.kt
#RunWith(RobolectricTestRunner::class)
#Config(application = TestApp::class)
class MainActivityUnitTest {
#Inject lateinit var eventsService: EventsService
#Before
fun setup() {
val testComponent = DaggerTestAppComponent.builder().build()
testComponent.inject(this)
}
#Test
fun givenActivityStarted_whenLoadFailed_shouldDisplayNoEventsMessage() {
val events = ArrayList<Event>()
doAnswer {
//this block is never hit during debug
val callback: ServiceCallback<List<Event>> = it.getArgument(0)
callback.onCompletion(events)
}.whenever(eventsService).getAllEvents(any())
val activity = Robolectric.buildActivity(MainActivity::class.java).create().start().visible().get()
val noEventsView = activity.findViewById(R.id.no_events) as View
//this always evaluates to null because the callback is never set from the doAnswer lambda
assertThat(callback).isNotNull()
verify(callback)!!.onCompletion(events)
assertThat(noEventsView.visibility).isEqualTo(View.VISIBLE)
}
}
Edit: Adding App and TestApp
open class App : Application() {
private val TAG = this::class.qualifiedName
lateinit var appComponent: AppComponent
override fun onCreate() {
super.onCreate()
appComponent = initDagger(this)
}
open fun initDagger(app: App): AppComponent {
return DaggerAppComponent.builder().appModule(AppModule(app)).build()
}
}
class TestApp : App() {
override fun initDagger(app: App): AppComponent {
return DaggerTestAppComponent.builder().build()
}
}
It looks like you're using a different component to inject your test and activity. As they're different components I suspect you are using 2 different instances of the eventsService.
Your test uses a local DaggerTestAppComponent.
#Inject lateinit var eventsService: EventsService
#Before
fun setup() {
val testComponent = DaggerTestAppComponent.builder().build()
testComponent.inject(this)
}
While your Activity uses the appComponent from the application.
class MainActivity : AppCompatActivity() {
#Inject lateinit var eventsService: EventsService
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
(application as App).appComponent.inject(this)
...
}
To overcome this you may consider adding a test version of your application class, this would allow you to replace the AppComponent in your application with your TestAppComponent. Robolectric should allow you to create a test application as follows: http://robolectric.org/custom-test-runner/
I am a newbie to android and trying to use Dagger2. I spend whole night and still dont know why my dagger does not provide presenter. Here are my code (I use Kotlin)
AppComponent
#Singleton
#Component(modules = arrayOf(PresenterModule::class))
interface AppComponent {
fun inject(target: SplashActivity)
}
PresenterModule
#Module
class PresenterModule {
#Provides
#Singleton
fun provideSplashPresenter(): SplashPresenter {
return SplashPresenter()
}
}
App
class App: Application() {
companion object {
lateinit var appComponent: AppComponent
}
override fun onCreate() {
super.onCreate()
appComponent = initDagger()
}
private fun initDagger(): AppComponent {
return DaggerAppComponent.create()
}
}
This is the presenter
class SplashPresenter: BasePresenterImpl<SplashContract.View>(), SplashContract.Presenter {
override fun performToast(mess: String) {
logi("abc", "performToast")
logi("abc", "mess: " + mess)
mView?.showLoading()
if (mess.isNullOrBlank()) {
mView?.showTosat("this is empty mess") ?: logi("abc", "null")
} else {
mView?.showTosat(mess) ?: logi("abc", "null")
}
mView?.hideLoading()
}
}
And finally, this is my SplashActivity
class SplashActivity : BaseActivity(), SplashContract.View {
#Inject
lateinit var presenter: SplashPresenter
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_splash)
presenter.attachView(this)
//TODO: check log in
//TODO: If logged in => start main screen
//TODO: If not logged in => load login activity
button.setOnClickListener{
presenter.performToast(editText.text.toString())
logi("abc", "perform clicked")
}
}
}
When I run these code, I got this error
Lateinit property presenter has not been initialized, which means that "Inject" does not work
Since you're not using constructor injection here (which you can't, because you don't 'own' the activity's constructor) Dagger does not 'know' that it has to inject something into your Activity.
You have to manually inject like this:
(applicationContext as App).appComponent.inject(this)
in your SplashActivity's onCreate() method (before using the presenter, of course).
Second, your presenter needs a constructor that tells Dagger how to construct/'build' the presenter, which means a constructor annotated with the #Inject annotation, so:
class SplashPresenter #Inject constructor(): BasePresenterImpl<SplashContract.View>(), SplashContract.Presenter
You forgot to inject the SplashActivity:
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
App.appComponent.inject(this)
setContentView(R.layout.activity_splash)
...
class SlideshowViewModel : ViewModel() {
#Inject lateinit var mediaItemRepository : MediaItemRepository
fun init() {
What goes here?
}
So I'm trying to learn Dagger2 so I can make my apps more testable. Problem is, I've already integrated Kotlin and am working on the Android Architectural components. I understand that constructor injection is preferable but this isn't possible with ViewModel. Instead, I can use lateinit in order to inject but I'm at a loss to figure out how to inject.
Do I need to create a Component for SlideshowViewModel, then inject it? Or do I use the Application component?
gradle:
apply plugin: 'com.android.application'
apply plugin: 'kotlin-android'
kapt {
generateStubs = true
}
dependencies {
compile "com.google.dagger:dagger:2.8"
annotationProcessor "com.google.dagger:dagger-compiler:2.8"
provided 'javax.annotation:jsr250-api:1.0'
compile 'javax.inject:javax.inject:1'
}
Application Component
#ApplicationScope
#Component (modules = PersistenceModule.class)
public interface ApplicationComponent {
void injectBaseApplication(BaseApplication baseApplication);
}
BaseApplication
private static ApplicationComponent component;
#Override
public void onCreate() {
super.onCreate();
component = DaggerApplicationComponent
.builder()
.contextModule(new ContextModule(this))
.build();
component.injectBaseApplication(this);
}
public static ApplicationComponent getComponent() {
return component;
}
You can enable constructor injection for your ViewModels. You can check out Google samples to see how to do it in Java. (Update: looks like they converted the project to Kotlin so this URL no longer works)
Here is how to do a similar thing in Kotlin:
Add ViewModelKey annotation:
import android.arch.lifecycle.ViewModel
import java.lang.annotation.Documented
import java.lang.annotation.ElementType
import java.lang.annotation.Retention
import java.lang.annotation.RetentionPolicy
import java.lang.annotation.Target
import dagger.MapKey
import kotlin.reflect.KClass
#Suppress("DEPRECATED_JAVA_ANNOTATION")
#Documented
#Target(ElementType.METHOD)
#Retention(RetentionPolicy.RUNTIME)
#MapKey
internal annotation class ViewModelKey(val value: KClass<out ViewModel>)
Add ViewModelFactory:
import android.arch.lifecycle.ViewModel
import android.arch.lifecycle.ViewModelProvider
import javax.inject.Inject
import javax.inject.Provider
import javax.inject.Singleton
#Singleton
class ViewModelFactory #Inject constructor(
private val creators: Map<Class<out ViewModel>, #JvmSuppressWildcards Provider<ViewModel>>
) : ViewModelProvider.Factory {
#Suppress("UNCHECKED_CAST")
override fun <T : ViewModel> create(modelClass: Class<T>): T {
var creator: Provider<out ViewModel>? = creators[modelClass]
if (creator == null) {
for ((key, value) in creators) {
if (modelClass.isAssignableFrom(key)) {
creator = value
break
}
}
}
if (creator == null) {
throw IllegalArgumentException("unknown model class " + modelClass)
}
try {
return creator.get() as T
} catch (e: Exception) {
throw RuntimeException(e)
}
}
}
Add ViewModelModule:
import dagger.Module
import android.arch.lifecycle.ViewModel
import dagger.multibindings.IntoMap
import dagger.Binds
import android.arch.lifecycle.ViewModelProvider
import com.bubelov.coins.ui.viewmodel.EditPlaceViewModel
#Module
abstract class ViewModelModule {
#Binds
#IntoMap
#ViewModelKey(EditPlaceViewModel::class) // PROVIDE YOUR OWN MODELS HERE
internal abstract fun bindEditPlaceViewModel(editPlaceViewModel: EditPlaceViewModel): ViewModel
#Binds
internal abstract fun bindViewModelFactory(factory: ViewModelFactory): ViewModelProvider.Factory
}
Register your ViewModelModule in your component
Inject ViewModelProvider.Factory in your activity:
#Inject lateinit var modelFactory: ViewModelProvider.Factory
private lateinit var model: EditPlaceViewModel
Pass your modelFactory to each ViewModelProviders.of method:
model = ViewModelProviders.of(this, modelFactory)[EditPlaceViewModel::class.java]
Here is the sample commit which contains all of the required changes: Support constructor injection for view models
Assuming you have a Repository class that can be injected by Dagger and a MyViewModel class that has a dependency on Repository defined as such:
class Repository #Inject constructor() {
...
}
class MyViewModel #Inject constructor(private val repository: Repository) : ViewModel() {
...
}
Now you can create your ViewModelProvider.Factory implementation:
class MyViewModelFactory #Inject constructor(private val myViewModelProvider: Provider<MyViewModel>) : ViewModelProvider.Factory {
#Suppress("UNCHECKED_CAST")
override fun <T : ViewModel> create(modelClass: Class<T>): T {
return myViewModelProvider.get() as T
}
}
Dagger setup does not look too complicated:
#Component(modules = [MyModule::class])
interface MyComponent {
fun inject(activity: MainActivity)
}
#Module
abstract class MyModule {
#Binds
abstract fun bindsViewModelFactory(factory: MyViewModelFactory): ViewModelProvider.Factory
}
Here's the activity class (might be fragment as well), where the actual injection takes place:
class MainActivity : AppCompatActivity() {
#Inject
lateinit var factory: ViewModelProvider.Factory
lateinit var viewModel: MyViewModel
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
// retrieve the component from application class
val component = MyApplication.getComponent()
component.inject(this)
viewModel = ViewModelProviders.of(this, factory).get(MyViewModel::class.java)
}
}
No. You create a component where you are declaring (using) your viewModel. It is normally an activity/fragment. The viewModel has dependencies (mediaitemrepository), so you need a factory. Something like this:
class MainViewModelFactory (
val repository: IExerciseRepository): ViewModelProvider.Factory {
#Suppress("UNCHECKED_CAST")
override fun <T : ViewModel?> create(p0: Class<T>?): T {
return MainViewModel(repository) as T
}
}
Then the dagger part (activity module)
#Provides
#ActivityScope
fun providesViewModelFactory(
exerciseRepos: IExerciseRepository
) = MainViewModelFactory(exerciseRepos)
#Provides
#ActivityScope
fun provideViewModel(
viewModelFactory: MainViewModelFactory
): MainViewModel {
return ViewModelProviders
.of(act, viewModelFactory)
.get(MainViewModel::class.java)
}
Refer to a repo I created when I was learning dagger+kotlin
Essentially you need a ViewModelFactory instance to the UI layer, you use that to create a viewmodel.
#AppScope
class ViewModelFactory
#Inject
constructor(private val creators: Map<Class<out ViewModel>, #JvmSuppressWildcards Provider<ViewModel>>)
: ViewModelProvider.Factory {
#SuppressWarnings("Unchecked")
override fun <T : ViewModel?> create(modelClass: Class<T>): T {
var creator = creators[modelClass]
if (creator == null) {
for (entry in creators) {
if (modelClass.isAssignableFrom(entry.key)) {
creator = entry.value
break
}
}
}
if (creator == null) throw IllegalArgumentException("Unknown model class" + modelClass)
try {
return creator.get() as T
} catch (e: Exception) {
throw RuntimeException(e)
}
}
}
Your ViewModelModule should look like (this is where you store all viewmodels).
#Module
abstract class ViewModelModule {
#AppScope
#Binds
#IntoMap
#ViewModelKey(YourViewModel::class)
abstract fun bindsYourViewModel(yourViewModel: YourViewModel): ViewModel
// Factory
#AppScope
#Binds abstract fun bindViewModelFactory(vmFactory: ViewModelFactory): ViewModelProvider.Factory
}
Then create a dagger map key
#Documented
#Target(AnnotationTarget.FUNCTION)
#Retention(AnnotationRetention.RUNTIME)
#MapKey
internal annotation class ViewModelKey(val value: KClass<out ViewModel>)
Then on your UI layer, inject the factory and instantiate your viewmodel using ViewModelProviders
class YourActivity : BaseActivity() {
#Inject
lateinit var viewModelFactory: ViewModelProvider.Factory
lateinit var yourViewModel: YourViewModel
override fun onCreate(savedInstanceState: Bundle?) {
...
...
(application as App).component.inject(this)
}
override fun onStart() {
super.onStart()
yourViewModel = ViewModelProviders.of(this, viewModelFactory).get(YourViewModel::class.java)
// you can now use your viewmodels properties and methods
yourViewModel.methodName()
yourViewModel.list.observe(this, { ... })
}
you expose the ViewModel on your component:
#Singleton
#Component(modules={...})
public interface SingletonComponent {
BrandsViewModel brandsViewModel();
}
And now you can access this method on the component inside the ViewModelFactory:
// #Inject
BrandsViewModel brandsViewModel;
...
brandsViewModel = new ViewModelProvider(this, new ViewModelProvider.Factory() {
#Override
public <T extends ViewModel> create(Class<T> modelClazz) {
if(modelClazz == BrandsViewModel.class) {
return singletonComponent.brandsViewModel();
}
throw new IllegalArgumentException("Unexpected class: [" + modelClazz + "]");
}).get(BrandsViewModel.class);
All this can be simplified and hidden with Kotlin:
inline fun <reified T: ViewModel> AppCompatActivity.createViewModel(crossinline factory: () -> T): T = T::class.java.let { clazz ->
ViewModelProvider(this, object: ViewModelProvider.Factory {
override fun <T : ViewModel?> create(modelClass: Class<T>): T {
if(modelClass == clazz) {
#Suppress("UNCHECKED_CAST")
return factory() as T
}
throw IllegalArgumentException("Unexpected argument: $modelClass")
}
}).get(clazz)
}
which now lets you do
brandsViewModel = createViewModel { singletonComponent.brandsViewModel() }
Where now BrandsViewModel can receive its parameters from Dagger:
class BrandsViewModel #Inject constructor(
private val appContext: Context,
/* other deps */
): ViewModel() {
...
}
Though the intent might be cleaner if a Provider<BrandsViewModel> is exposed from Dagger instead
interface SingletonComponent {
fun brandsViewModel(): Provider<BrandsViewModel>
}
brandsViewModel = createViewModel { singletonComponent.brandsViewModel().get() }
Try with below code :
#Provides
#Singleton
fun provideRepository(): Repository {
return Repository(DataSource())
}
I wrote a library that should make this more straightforward and way cleaner, no multibindings or factory boilerplate needed, while also giving the ability to further parametrise the ViewModel at runtime:
https://github.com/radutopor/ViewModelFactory
#ViewModelFactory
class UserViewModel(#Provided repository: Repository, userId: Int) : ViewModel() {
val greeting = MutableLiveData<String>()
init {
val user = repository.getUser(userId)
greeting.value = "Hello, $user.name"
}
}
In the view:
class UserActivity : AppCompatActivity() {
#Inject
lateinit var userViewModelFactory2: UserViewModelFactory2
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_user)
appComponent.inject(this)
val userId = intent.getIntExtra("USER_ID", -1)
val viewModel = ViewModelProviders.of(this, userViewModelFactory2.create(userId))
.get(UserViewModel::class.java)
viewModel.greeting.observe(this, Observer { greetingText ->
greetingTextView.text = greetingText
})
}
}
Here is my solution using reflection.
Let's say for simplicity you have AppComponent
#AppScope
#Component(modules = [AppModule::class])
interface AppComponent {
fun getAppContext(): Context
fun getRepository(): Repository
fun inject(someViewModel: SomeViewModel)
class App : Application() {
companion object {
lateinit var appComponent: AppComponent
private set
}
...
}
fun appComponent() = App.appComponent
And you need inject SomeViewModel class
class SomeViewModel: ViewModel() {
#Inject
lateinit var repository: Repository
}
Create custom lazy property delegate
inline fun <reified T: ViewModel> Fragment.viewModel(component: Any?) = lazy {
val vm = ViewModelProvider(this).get(T::class.java)
component?.let {
val m = component.javaClass.getMethod("inject", T::class.java)
m.invoke(component, vm)
}
vm
}
And use it
class SomeFragment: Fragment() {
private val vm: SomeViewModel by viewModel(appComponent())
...
}
With the solution below, I found I can use injection anywhere I want by including this line in the init or onCreate methods (No factories needed, so it works with ViewModel and WorkManager)
Injector.getComponent().inject(this)
BaseApplication
class BaseApplication : Application() {
lateinit var applicationComponent: ApplicationComponent
override fun onCreate() {
super.onCreate()
INSTANCE = this
applicationComponent = DaggerApplicationComponent
.builder()
//Add your modules like you did in your question above
.build()
}
companion object {
private var INSTANCE: BaseApplication? = null
#JvmStatic
fun get(): BaseApplication= INSTANCE!!
}
}
Injector
class Injector private constructor() {
companion object {
#JvmStatic
fun getComponent(): ApplicationComponent = BaseApplication.get().applicationComponent
}
}
Essentially, you access applicationComponent with a static method. With that, you should be able to inject any class you've made an inject method for in your component with this line:
Injector.getComponent().inject(this)
in your case
init{
Injector.getComponent().inject(this)
}