I have followed the instructions in Google Codelab about the Saved state module.
My gradle dependency is:
implementation "androidx.lifecycle:lifecycle-viewmodel-savedstate:1.0.0-rc03"
My View Model factory is:
class MyViewModelFactory(val repository: AppRepository, owner: SavedStateRegistryOwner,
defaultArgs: Bundle? = null) : AbstractSavedStateViewModelFactory(owner, defaultArgs) {
override fun <T : ViewModel?> create(
key: String,
modelClass: Class<T>,
handle: SavedStateHandle): T {
return MyViewModel(repository, handle) as T
}
}
My View model:
class MyViewModel constructor(val repository: AppRepository, private val savedStateHandle: SavedStateHandle): ViewModel() {
fun getMyParameter(): LiveData<Int?> {
return savedStateHandle.getLiveData(MY_FIELD)
}
fun setMyParameter(val: Int) {
savedStateHandle.set(MY_FIELD, val)
}
}
My Fragment:
class MyFragment : androidx.fragment.app.Fragment() {
override fun onCreate(savedInstanceState: Bundle?) {
arguments?.let {
var myField = it.getInt(MY_FIELD)
activitiesViewModel.setMySavedValue(myField ?: 0)
}
}
}
When the app is being used, the live data for the saved state field updates correctly. But as soon as I put the app in background (and I set "don't keep activities" in developer options), and then re open app, the live data shows a value as if it was never set. In other words, the saved state handle seems to forget the field I am trying to save.
Any thoughts?
I had the same problem. It was solved by the fact that I stopped requesting saved values from SavedStateHandle in the onRestoreInstanceState method. This call is correctly used in the onCreate method.
Related
In NotificationListener, I want to implement code to perform different functions according to the state value of the switch element in activity_main.xml.
So inside the onNotificationPosted() function
I need to know the state of the switch through the following code.
val volumeSeekBar:Switch = findViewById(R.id.switch_id)
To do this, I wrote the following code, and it turns off as soon as the app is launched.
How to access the switch element of Mainactivity in a class that inherits NotificationListenerService ??
NotificationListener.kt
class NotificationListener(activity:MainActivity) : NotificationListenerService() {
override fun onCreate() {
...
}
override fun onListenerConnected() {
...
}
override fun onNotificationPosted(sbn: StatusBarNotification) {
val volumeSeekBar:Switch = activity.findViewById(R.id.switch_id) <-- doesn't work
}
}
I use Jetpack Compose and have 2 screens. When I open second screen and back to the fisrt, flow variable calling again and ui updated again. But, I don't understand why... When I use liveData was working perfect.
My code with LiveData:
class MainViewModel(private val roomRepository: Repository, private val sPref:SharedPreferences) : ViewModel() {
val words: LiveData<List<WordModel>> by lazy {
roomRepository.getAllWords()
}
...
}
MainScreen.kt:
#ExperimentalMaterialApi
#Composable
fun MainScreen(viewModel: MainViewModel) {
...
val words: List<WordModel> by viewModel
.words
.observeAsState(listOf())
...
WordList(
words = words,
onNoticeClick = { viewModel.onWordClick(it) },
state = textState,
lazyState = viewModel.listState!!
)
...
}
#Composable
private fun WordList(
words: List<WordModel>,
onNoticeClick: (WordModel) -> Unit,
state: MutableState<TextFieldValue>,
lazyState: LazyListState
) {
var filteredCountries: List<WordModel>
LazyColumn(state = lazyState) {
val searchedText = state.value.text
filteredCountries = if (searchedText.isEmpty()) {
words
} else {
words.filter {
it.word.lowercase().contains(searchedText) || it.translation.lowercase()
.contains(searchedText)
}
}
items(count = filteredCountries.size) { noteIndex ->
val note = filteredCountries[noteIndex]
Word(
word = note,
onWordClick = onNoticeClick
)
}
}
}
WordDao.kt:
#Dao
interface WordDao {
#Query("SELECT * FROM WordDbModel")
fun getAll(): LiveData<List<WordDbModel>>
}
RoomRepositoryImpl.kt:
class RoomRepositoryImpl(
private val wordDao: WordDao,
private val noticeDao: NoticeDao,
private val dbMapper: DbMapper
) : Repository {
override fun getAllWords(): LiveData<List<WordModel>> =
Transformations.map(wordDao.getAll()) {dbMapper.mapWords(it)}
...
}
DbMapperImpl.kt:
class DbMapperImpl: DbMapper {
...
override fun mapWords(words: List<WordDbModel>): List<WordModel> =
words.map { word -> mapWord(word, listOf<NoticeModel>()) }
}
My code with Flow, which calling every time when open the first screen:
class MainViewModel(private val roomRepository: Repository, private val sPref:SharedPreferences) : ViewModel() {
val words: Flow<List<WordModel>> = flow {
emitAll(repository.getAllWords())
}
}
MainScreen.kt:
#ExperimentalMaterialApi
#Composable
fun MainScreen(viewModel: MainViewModel) {
...
val words: List<WordModel> by viewModel
.words
.collectAsState(initial = listOf())
...
}
WordDao.kt:
#Dao
interface WordDao {
#Query("SELECT * FROM WordDbModel")
fun getAll(): Flow<List<WordDbModel>>
}
RoomRepositoryImpl.kt:
class RoomRepositoryImpl(
private val wordDao: WordDao,
private val noticeDao: NoticeDao,
private val dbMapper: DbMapper
) : Repository {
override fun getWords(): Flow<List<WordModel>> = wordDao.getAll().map { dbMapper.mapWords(it) }
}
And my router from MainRouting.kt:
sealed class Screen {
object Main : Screen()
object Notice : Screen()
object Your : Screen()
object Favorites : Screen()
}
object MainRouter {
var currentScreen: Screen by mutableStateOf(Screen.Main)
var beforeScreen: Screen? = null
fun navigateTo(destination: Screen) {
beforeScreen = currentScreen
currentScreen = destination
}
}
And MainActivity.kt:
class MainActivity : ComponentActivity() {
...
#Composable
#ExperimentalMaterialApi
private fun MainActivityScreen(viewModel: MainViewModel) {
Surface {
when (MainRouter.currentScreen) {
is Screen.Main -> MainScreen(viewModel)
is Screen.Your -> MainScreen(viewModel)
is Screen.Favorites -> MainScreen(viewModel)
is Screen.Notice -> NoticeScreen(viewModel = viewModel)
}
}
}
...
}
Perhaps someone knows why a new drawing does not occur with liveData (or, it is performed so quickly that it is not noticeable that it is), but with Flow the drawing of the list is visible.
You're passing the viewModel around, which is a terrible practice in a framework like Compose. The Model is like a waiter. It hangs around you, serves you water, does its job while you make the order. As you get distracted talking, it leaves. When it comes back, it is not the same waiter you had earlier. It wears the same uniform, with the same characteristics, but is still essentially a different object. When you pass the model around, it gets destroyed in the process of navigation. In case of flow, you are getting biased. Notice how you manually do a lazy initialization for the LiveData, but a standard proc. for Flow? Seems like the only logical reason for your observed inconsistency. If you want to use Flow in your calls instead of LiveData, just convert it at the site of initialization in the ViewModel. Your symptoms should go away.
I am writing a Kotlin app and using Firebase for authentication.
As onActivityResult is now depraceted, I am trying to migrate my app to use registerForActivityResult. I have a link to Google account feature, that starts with the Google sign-in flow, as shown here. My code:
private fun initGoogleSignInClient() =
activity?.let {
// Configure Google Sign In
val gso =
GoogleSignInOptions.Builder(GoogleSignInOptions.DEFAULT_SIGN_IN)
.requestIdToken(getString(R.string.default_web_client_id))
.requestEmail()
.build()
// Build a GoogleSignInClient with the options specified by gso.
viewModel.googleSignInClient = GoogleSignIn.getClient(it, gso)
}
private fun showLinkWithGoogle() =
startActivityForResult(viewModel.googleSignInClient.signInIntent, RC_LINK_GOOGLE)
Where initGoogleSignInClient is called in the fragment's onCreateView, and showLinkWithGoogle is called when the user taps the button on the screen. This workes perfectly.
I looked for an example using registerForActivityResult, and the best one I found was at the bottom of this page. I added this code:
private val linkWithGoogle =
registerForActivityResult(ActivityResultContracts.StartIntentSenderForResult()) {
viewModel.handleGoogleResult(it.data)
}
private fun showLinkWithGoogle() =
linkWithGoogle.launch(IntentSenderRequest.Builder(viewModel.googleSignInClient.signInIntent))
But realized that IntentSenderRequest.Builder needs an IntentSender and not an Intent. I haven't found any example of how to build an IntentSender from an Intent, nor a way to get one from my GoogleSignInClient.
Could anyone please provide a full example of using registerForActivityResult(ActivityResultContracts.StartIntentSenderForResult())?
Thank you very much!
For this use-case, you don't need an ActivityResultContracts of type StartIntentSenderForResult but one of type StartActivityForResult. Here is an example (since you did not provide your full implementation):
Fragment
private val googleRegisterResult =
registerForActivityResult(ActivityResultContracts.StartActivityForResult()) { result ->
result.checkResultAndExecute {
val task = GoogleSignIn.getSignedInAccountFromIntent(data)
val account = task.getResult(ApiException::class.java)
loginViewModel.onEvent(LoginRegistrationEvent.SignInWithGoogle(account))
}.onFailure { e -> toast("Error: ${e.message}") }
}
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
myGoogleSignInButton.setOnClickListener {
googleRegisterResult.launch(viewModel.googleSignInClient.signInIntent)
}
}
Then, in your viewmodel, you can handle the login as you would usually do, the only difference is, that you no longer need an RC_SIGN_IN
ViewModel Example
class YourViewModel : ViewModel() {
fun onEvent(event: LoginRegistrationEvent) {
when(event) {
is LoginRegistrationEvent.SignInWithGoogle -> {
viewModelScope.launch {
val credential = GoogleAuthProvider.getCredential(event.account.idToken)
Firebase.auth.signInWithCredential(credential).await()
}
}
}
}
}
To make my life easier, I created an extension function, that checks, if the login was successful and then executes a block of code (in this case, getting the account), while caching any exceptions. Futhermore, inside your block, you have access to an instance of ActivityResult as this:
inline fun ActivityResult.checkResultAndExecute(block: ActivityResult.() -> Unit) =
if (resultCode == Activity.RESULT_OK) runCatching(block)
else Result.failure(Exception("Something went wrong"))
suppose there are 2 classes:
class MyLiveData:LiveData<Int>()
class MyMutableLiveData:MutableLiveData<Int>()
Casting from MutableLiveData to LiveData is permitted:
val ld1=MutableLiveData<Int>()
val ld2:LiveData<Int> = ld1 //ok
But you can't cast your own implementations this way:
val mutable=MyMutableLiveData()
val immutable:MyLiveData = mutable //type missmatch
I understand that MutableLiveData extends LiveData thats why they are castable.But I can't have MyMutableLiveData extending MyLiveData as it won't be mutable in this case
Are there any workarounds?
UPD:I guess I need to show motivation of extending LiveData.I'm trying to implement MutableLiveDataCollection which notifies not just value changes via setValue/postValue but also value modification like adding new elements.I'm surprised there is no native solution for this.
Anyway to obseve modify events there have to be additional observe method.And this method have to be inside immutable part aka LiveDataCollection because views will call it.Inheritance is natural solution here IMHO.
The key idea sits in the MutableLiveData class.The only thing this class does - is it changes access modifiers on setValue/postValue methods.I can do the same trick.Therefore the final code will be:
open class LiveDataCollection<K,
L:MutableCollection<K>,
M:Collection<K>>: LiveData<L>() {
private var active=false
private var diffObservers = ArrayList<Observer<M>>()
fun observe(owner: LifecycleOwner, valueObserver: Observer<L>, diffObserver: Observer<M>) {
super.observe(owner,valueObserver)
diffObservers.add(diffObserver)
}
protected open fun addItems(toAdd:M) {
value?.addAll(toAdd)
if (active)
for (observer in diffObservers)
observer.onChanged(toAdd)
}
override fun removeObservers(owner: LifecycleOwner) {
super.removeObservers(owner)
diffObservers= ArrayList()
}
override fun onActive() {
super.onActive()
active=true
}
override fun onInactive() {
super.onInactive()
active=false
}
}
class MutableLiveDataCollection<K,L:MutableCollection<K>,
M:Collection<K>>: LiveDataCollection<K,L,M>() {
public override fun addItems(toAdd:M) {
super.addItems(toAdd)
}
public override fun postValue(value: L) {
super.postValue(value)
}
public override fun setValue(value: L) {
super.setValue(value)
}
}
I made a special sealed class to validate my nullable URLs so I can safely and easily know it's state (None, Invalid, Valid)
sealed class UrlType : Parcelable {
#Parcelize class Valid private constructor(val url: String) : UrlType() {
companion object : CompanionTest<UrlType.Valid, String>(::Valid)
}
#Parcelize object None : UrlType()
#Parcelize class Invalid(val invalidUrl: String) : UrlType()
companion object {
fun getUrlType(url: String?): UrlType {
return if (url == null) {
UrlType.None
} else if (!url.isValidUrl()) {
UrlType.Invalid(url)
} else {
Valid.create(url)
}
}
}
}
open class CompanionTest<out T, in A>(creator: (A) -> T) {
private var creator: ((A) -> T)? = creator
fun create(arg1: A): T {
return creator!!(arg1)
}
}
#Parcelize
data class NewsPost(
val id: String,
val title: String,
val description: String?,
val webContentUrl: UrlType,
val imageUrl: UrlType,
val created: String,
val updated: String,
val feeds: List<Feed>
) : Parcelable
When I was first trying out the idea, I had my suspicions that it wouldn't work because of the private constructor and Parcelize but I did some tests and it did work.
I also have a sealed class to indicate a launch type for my activity which can be entered from multiple paths
sealed class NewsLaunchType : Parcelable {
#Parcelize object FeedList : NewsLaunchType()
#Parcelize class FeedDetail(val newsFeedType: NewsFeedType) : NewsLaunchType()
#Parcelize class PostDetail(val newsPost: NewsPost) : NewsLaunchType()
}
When I go to launch my activity with a NewsLaunchType.PostDetail(newsPost) the app is crashing with the following error
fun startActivity(){
val intent = Intent(context, NewsActivity::class.java).apply {
putExtra("key", NewsLaunchType.PostDetail(newsPost))
}
startActivity(intent)
}
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_news)
val newsActivityLaunchType = intent.getParcelableExtra<NewsLaunchType>("key")
}
2018-11-08 11:08:33.897 17030-17030/com.something.internal E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.something.internal, PID: 17030
java.lang.IllegalAccessError: Method 'void com.something.somethingkit.helper.UrlType$Valid.<init>(java.lang.String)' is inaccessible to class 'com.something.somethingkit.helper.UrlType$Valid$Creator' (declaration of 'com.something.somethingkit.helper.UrlType$Valid$Creator' appears in /data/app/com.something.internal-QTiupS4yw25rZK5uXP7UCQ==/base.apk:classes2.dex)
at com.something.somethingkit.helper.UrlType$Valid$Creator.createFromParcel(Unknown Source:11)
at android.os.Parcel.readParcelable(Parcel.java:2798)
at com.something.somethingkit.model.news.local.NewsPost$Creator.createFromParcel(Unknown Source:25)
at android.os.Parcel.readParcelable(Parcel.java:2798)
at com.something.screens.news.NewsLaunchType$PostDetail$Creator.createFromParcel(Unknown Source:13)
at android.os.Parcel.readParcelable(Parcel.java:2798)
at android.os.Parcel.readValue(Parcel.java:2692)
at android.os.Parcel.readArrayMapInternal(Parcel.java:3059)
at android.os.BaseBundle.unparcel(BaseBundle.java:257)
at android.os.Bundle.getParcelable(Bundle.java:888)
at android.content.Intent.getParcelableExtra(Intent.java:7734)
at com.something.screens.news.NewsActivity.onCreate(NewsActivity.kt:31)
at android.app.Activity.performCreate(Activity.java:7183)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1220)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2908)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3030)
at android.app.ActivityThread.-wrap11(Unknown Source:0)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1696)
at android.os.Handler.dispatchMessage(Handler.java:105)
at android.os.Looper.loop(Looper.java:164)
at android.app.ActivityThread.main(ActivityThread.java:6938)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:327)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1374)
Now that's not entirely unexpected, except that it does work if I try to pull it out within the same location I created it in
fun startActivity(){
val intent = Intent(context, NewsActivity::class.java).apply {
putExtra("key", NewsLaunchType.PostDetail(newsPost))
}
val test = intent.getParcelableExtra<NewsLaunchType>("key")
startActivity(intent)
}
It also works if I add it to a fragment bundle, and add/replace a new fragment into my activity.
companion object {
fun newInstance(newsPost: NewsPost): NewsDetailFragment {
val bundle = Bundle()
bundle.putParcelable(extraNewsPost, newsPost)
val fragment = NewsDetailFragment()
fragment.arguments = bundle
return fragment
}
}
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
val newsPost = arguments?.getParcelable<NewsPost>(extraNewsPost)
}
Note - When passing it across activities, there is an extra layer of Sealed Classes going on, but it will crash as well if I simply tried to pass a NewsPost across activities, so the extra layer is not the issue.
This seems like it might be a bug with the Kotlin Parcelize feature.
Is there any reason why passing it across activities would throw an error but passing it between fragments doesn't? If there is a reason... any suggestions on how I could pass this across activities?
The docs clearly state:
The primary constructor should be accessible (non-private)
Not sure why it's working when passing to fragment and not working when passing to activity.
In my case, I solved this issue by making my class constructor internal.