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Hi everyone, I am a Kotlin Flow learner. I am wondering if there is a way to get a ViewModel instance observing the state change in a Flow instance, for instance a new value is added in and ready to be collected? I am felling I might misunderstand the concept of the Flow or miss some key information. Could anyone help me? Thanks in advance!

I've got the following ViewModel:

class FundamentalsViewModel: ViewModel() {

    var fundamentalsLiveData = MutableLiveData<WrappedResult<PriceDataResponse>>()
    private val repository = FundamentalsRespository()
    private var job: Job? = null

    fun getData(symbol: String) {
        if(job == null || job?.isActive == false) {
            fundamentalsLiveData.value = WrappedResult.Loading
            job = viewModelScope.launch(<http://Dispatchers.IO|Dispatchers.IO>) {
                try {
                    val response = repository.getData(symbol)
                    withContext(Dispatchers.Main) {
                        fundamentalsLiveData.value = WrappedResult.Success(response)
                    }
                } catch(e: Exception) {
                    withContext(Dispatchers.Main) {
  						fundamentalsLiveData.value = WrappedResult.Failure(e)
                    }
                }
            }
        }
    }
}

And out in the field I'm getting a crash that says this:

Fatal Exception: java.lang.NullPointerException
Parameter specified as non-null is null: method kotlin.j0.d.u.p, parameter symbol

On the line that is:

fundamentalsLiveData.value = WrappedResult.Loading

How is it possible that there is ANY NPE here? It makes no sense to me. The WrappedResult is a typical Kotlin sealed class that looks like this:

sealed class WrappedResult<out T> {
    data class Success<out T: Any>(val data:T) : WrappedResult<T>()
    data class Failure(val error: Throwable) : WrappedResult<Nothing>()
    data class CallFailure(val error: String) : WrappedResult<Nothing>()
    object Loading : WrappedResult<Nothing>()
}

Any ideas would be appreciated!

After migrating to

Kotlin 1.4.0

in my Android project (AGP 4.0.1) when i want to build a release apk there are errors in console:

Warning: class [META-INF/versions/9/module-info.class] unexpectedly contains class [module-info]
Note: duplicate definition of program class [module-info]
Note: there were 20 duplicate class definitions.
      (<http://proguard.sourceforge.net/manual/troubleshooting.html#duplicateclass>)
Warning: there were 21 classes in incorrectly named files.
         You should make sure all file names correspond to their class names.
         The directory hierarchies must correspond to the package hierarchies.

Anyone has idea to resolve this issue?

So, maybe this is an Android Studio thing, but after upgrading to Kotlin 1.4.0, AS keeps reporting all of the new language features of 1.4 as red squiggly errors, though it compiles just fine. To get around this, we had to explicitly add the following to our build.gradle files

kotlinOptions {
    languageVersion = "1.4"
}

Did those of you using 1.4 have to do this? We're using AS 4.0.1, and we've got the Kotlin 1.4.10-release-Studio4.0-1 plugin installed in AS.

Hi all, wondering whether you all tend to include or exclude tax when you decide on pricing your apps in the app store?

For anyone who uses RxJava with Room, do you always error handle your subscriptions?

Hey @Ian Lake, what would be the solution to avoid this happening? https://issuetracker.google.com/issues/168779518 We have an app that creates fragments upon item selection in a RV and AFAIK, calling

popBackstackImmediate()

to go back invalidates the fragment and queues it for GC. We're calling

registerForActivityResult

in those fragments which eventually causes this overflow if the user stays in the app for long enough because our

registerForActivityResult

calls keep incrementing the counter.

Looking for an idiomatic way to perform some long running background Job in the viewmodel such that the work will be paused when the user navigates forward, resumed when the user navigates back to the fragment, and cancelled when the user navigates back from that fragment. I know the viewLifecycleOwner is probably useful for that and that the viewmodel can implement

LifecycleObserver

to observe the fragment lifecycle, but what I’m struggling with is a mechanism of how best to use these callbacks to control the work.

Hello everyone 👋 I've got a question regarding playing a video full screen portrait. The videos are typically 16:9 or 4:3 aspect ratio, and the videos are recorded in portrait orientation only (this is enforced while recording). Is there a way to play these videos in full screen portrait? That is, I want them to scale and keep aspect ratio intact to match the width/height of the parent container. Something similar to ImageView.ScaleType.CENTER_CROP. Essentially I want the video to fill the entire screen just like how popular apps like instagram and snapchat play video in full screen portrait. I'm using PlayerView from ExoPlayer UI lib and setting height/width to match_parent. PlayerView supports passing a

resize_mode

and I believe the default is

fit

which translates to

ImageView.ScaleType.CENTER_INSIDE

There's also a

fill

and

zoom

but these don't seem to keep the aspect ratio intact and stretch the video. Anyone have any idea if there is some straightforward combination of settings that I may be missing in order to achieve "center_crop" scaling and get the video to show full screen? The easy alternative is to set a black background for letter boxing and playing the video in it's actual aspect ratio, but the fullscreen is definitely preferred.

Hi all! I have a navigation component and I am wondering about transitions while I am changing graphs. The case: I have a graph, which shows a start screen, a login flow and a logged in graph:

<MainNavGraph>
    <StartFragment>
    <LoginFlowGraph>
         <UsernameFragment>
         <PasswordFragment>
    </LoginFlowGraph>
    <LoggedInGraph>
         <HomeFragment>
    </LoggedInGraph>
</MainNavGraph>

My problem is this: when I am logged in, I want to go to the LoggedInGraph and pop everything what is on the backstack:

if (!navController.currentDestination.isPartOfGraph(R.id.loggedInNavGraph)) {
	navController.popBackStack(R.id.mainNavGraph, false)
	navController.navigate(R.id.loggedInNavGraph)
}

This works fine. The graph is basically emptied to the root and then the loggedInNavGraph starts. I want to use material transitions during this, On the login flow I use Material shared transition on the X axis

enterTransition = MaterialSharedAxis(MaterialSharedAxis.X, true)
returnTransition = MaterialSharedAxis(MaterialSharedAxis.X, false)

On the HomeFragment I use transitions on the Z axis:

enterTransition = MaterialSharedAxis(MaterialSharedAxis.Z, true)
returnTransition = MaterialSharedAxis(MaterialSharedAxis.Z, false)

However, popping the backstack after the login flow, shows the fragments in the backstack also with the wrong animation... Is it possible to clear the backstack without the fragments from within the backstack to show themselves during the transition?

Is it necessary to call removeObserver for LiveData in a retained fragment? If so, where and when should this be done?

Hi all, I'm using GoogleSignInClient for logging the user into my app and I have a backend api to verify the TokenId (Jwt). For subsequent request to my backend api, I uses the same TokenId (Jwt) for authentication. But the token only valid for an hour, what's the recommended way to refresh the token? Do I do a .silentSignIn() to get a new token or should the backend api retrieve a new token and passes it back to the android app?

Hi @zsmb do you have any tips for using the BottomSheetDialogFragment with RainbowCake ?

Hey. I'm looking to build a Kotlin android app from scratch, something I could use on my portfolio for jobseeking. But with hundreds of thousands of apps already live, how does one choose what kind of app to build? (I've done Udacity's android developer nanodegree (java), so have a few projects on github. I also just finished Antonio Leiva's Kotlin for android online course, hence my current situation)

Hi there! Is there really no way to iterate in Kotlin/Java over graphenes/runes like “👨‍👩‍👧‍👧”?

A: count = 1, utf16 = 1, unicode scalars = 1 -> ['A']
€: count = 1, utf16 = 1, unicode scalars = 1 -> ['€']
➜: count = 1, utf16 = 1, unicode scalars = 1 -> ['➜']
⛳: count = 1, utf16 = 1, unicode scalars = 1 -> ['⛳']
💩: count = 1, utf16 = 2, unicode scalars = 1 -> ['💩']
❤️: count = 1, utf16 = 2, unicode scalars = 2 -> ['❤', '️']
👨‍👩‍👧‍👦: count = 1, utf16 = 11, unicode scalars = 7 -> ['👨', '‍', '👩', '‍', '👧', '‍', '👦']
👩‍❤️‍💋‍👩: count = 1, utf16 = 11, unicode scalars = 8 -> ['👩', '‍', '❤', '️', '‍', '💋', '‍', '👩']

In swift it’s just

text.count

and it returns number of characters like “👨‍👩‍👧‍👧”. I tried

@Test
    public void printBreak() {
        BreakIterator iterator = BreakIterator.getCharacterInstance();
        String[] tests = {
                "\uD83D\uDC68\u200D\uD83D\uDC69\u200D\uD83D\uDC67\u200D\uD83D\uDC67", // family icon 👨‍👩‍👧‍👧
                "💩",
                "€"
        };
        for (String test: tests) {
            iterator.setText(test);
            int index = iterator.first();
            System.out.println("!!!! Start " + test);
            while (index != BreakIterator.DONE) {
                System.out.println(index);
                index = iterator.next();
            }
            System.out.println("!!!! End " + test);
        }
    }

as article https://engineering.linecorp.com/en/blog/the-7-ways-of-counting-characters/ suggested but it also iterates over unicode scalars like

!!!! Start 👨‍👩‍👧‍👧
0
2
3
5
6
8
9
11
!!!! End 👨‍👩‍👧‍👧

Is it really so rocket science to iterate over multiple-characters in Android?

I wrote a library that allows you to generate a dagger module with a single binding. The idea being that you can use this with Dagger-Hilt and its new

@UninstallModules

annotation to replace a single binding in your tests rather than having to manually write those dagger modules yourself https://github.com/JuulLabs/pommel

How can I get current location? I have tried

FusedLocationProviderClient

but unfortunately,

lastLocation

does not provide the correct location.

hello. Has any1 had problem animating a view with MaterialContainerTransform inside a MotionLayout. For some reason, the animation glitches for me

Is this normal to set a nullable properties in Entity and Model class? Should we use non null "val" instead?

data class DataInputEntity(
    @PrimaryKey(autoGenerate = true)
    @ColumnInfo(name = "id") val id: Int,
    @ColumnInfo(name = "weight") var weight: Float? = null,
    @ColumnInfo(name = "body_fat") val bodyFat: Float? = null,
    @ColumnInfo(name = "stamp") val stamp: String,
    @ColumnInfo(name = "note") val note: String,
    @ColumnInfo(name = "date") val date: Long,
    @ColumnInfo(name = "unit") val weightUnit: Int = TypeUnitWeight.KG.value
)

For MotionLayout: does someone know how to transition to a State/ConstraintSet instantly (skipping the transition)?

LazyColumnFor items ripple effect is laggy. Is this an issue with compose?

Hi there, I have a question about navigation components and navigating from one bottom sheet to another bottom sheet. On Bottom Sheet A I have an option that does the following:

dismiss()
findNavController().navigate(
    R.id.action_bottom_sheet_b,
    bundleOf(...)
)

It opens the Bottom Sheet B without any problem, but if I rotate the screen I get a crash:

java.lang.IllegalStateException
DialogFragment NUM doesn't exist in the FragmentManager

If I move the

dismiss

after the

navigate

, Bottom Sheet B doesnt show up. Seems they are in the same transaction and therefore bottom sheet B gets dismised as well. Here is my navigation.xml

<dialog
    android:id="@+id/bottom_sheet_a"
    android:name="...BottomSheetA"
    tools:layout="@layout/dialog_bottom_sheet_a">

    <action
        android:id="@+id/action_bottom_sheet_b"
        app:destination="@id/bottom_sheet_b"/>

</dialog>

I found this on stack: https://stackoverflow.com/questions/56647476/why-dialog-does-not-have-a-navcontroller-missing And this: https://issuetracker.google.com/issues/134089818 which seems got resolved in 2.1.0-alpha06 But not sure it's the same issue. I'm using 2.3.0. If I use child

childFragmentManager.beginTransaction().show()

to show bottom sheet A instead of

findNavController().navigate()

, bottom sheet B gets displayed fine, no crash either. Any ideas of how to fix this?

kotlinx.serialization

recently added the ability to derive a serializer from external classes with properties-only primary constructors: https://github.com/Kotlin/kotlinx.serialization/blob/v1.0.0-RC2/docs/serializers.md#deriving-external-serializer-for-another-kotlin-class-experimental Are there plans to add support for this sort of feature for

@Parcelize

?

Hi, are you guys encounter this problem

Dependent features configured but no package ID was set.

I'm trying to set the project as modular as possible. Trying to access the theme from another module which is a

Composable

function to my main app module.

Anyone ran into issues using kotlin REPL in android studios , WARN: error in opening zip file: /Users/robertkeazor/.gradle/caches/transforms-2/files-2.1/d12ae88f0ff0382cb6bf0028c8ac549d/constraintlayout-2.0.1/AndroidManifest.xml java.util.zip.ZipException: error in opening zip file

I/art: Background partial concurrent mark sweep GC freed 37518(2MB) AllocSpace objects, 7(1348KB) LOS objects, 14% free, 22MB/26MB,

D/View: [ANR Warning]onMeasure time too long, this =androidx.constraintlayout.widget.ConstraintLayout{b5b15d4 V.E...... ......ID 0,0-720,2380}time =419 ms

how to reduce my app freezing

For those using Coroutines... Do you have your own custom "global scope". If so, do you cancel it? I'm creating a global scope (includes our thread pool)... But I wonder if I need to cancel it or it's children due to some lifecycle. Only one would be application lifecycle but not sure if it marrers. Thoughts?