Hi 👋 😄 Does anyone know if it is possible to do a linear transformation on the canvas in jetpack compose? So what I mean is mapping each point (u, v) on for instance an arch to (x, y) based on a function f so that f(u, v) = (x, y). Is that possible? 🙂 Is there any good docs on how to do that if it is possible? 🙂

Hi folks, I'm trying to figure out how to change text color based on the

initialState

value within

AnimatedContent

. Using the AnimatedContent example from the Android docs which slides number up/down based on the previous

initialState

, I've tried updateTransition along with

animateColor

but I can't find a way to change the text color based on the previous value. Am I missing something obvious here? 🤔

is there a live, online showcase of available Compose Multiplatform components, like we have for Kotlin MUI?

Hello there. We have main app navigation inside the scaffold. Scaffold provide padding values and we pass this padding to app navigation. How to make on clean way that screens that does not need this padding just exclude it? Ok I can make main viewmodel and control this behaviour but this sounds somehow wrong. Any advice maybe?

Hey guys, does anyone know if there's an official API support or something that can enable fast scrolling for a LazyColumn?

Hi. we are using ExposedDropdownMenuBox and ExposedDropdownMenu to display a list of numbers to select from.. Does anyone know if there is a way to have a scrollbar with this set up?

why would this not work

@Composable
fun Chip(
    label: String,
    enabled: MutableState<Boolean>,
    onClick: () -> Unit,
) {
    val (selected, setSelected) = enabled

    val chipColor =
        if (selected) MaterialTheme.colors.Action else MaterialTheme.colors.ForegroundMuted

    Surface(
        shape = RoundedCornerShape(15.dp),
        color = chipColor.copy(alpha = 0.2f),
        border = BorderStroke(
            width = 1.dp, color = chipColor
        ),
        modifier = Modifier
            .toggleable(
                value = selected,
                enabled = true,
                onValueChange = setSelected
            )
            .clickable {
                onClick()
            },

but this would

modifier = Modifier
            .clickable {
                onClick()
                setSelected(!selected)
            },

Thanks

I've got the following:

val rotation by animateFloatAsState(
        targetValue = if (state) 360.0f else 0f, 
        animationSpec = if (state) InfiniteRepeatableSpec(tween(durationMillis = 500, easing = LinearEasing)) else snap())

Which I use to rotate an image of a fan when the fan is on, and when it is off, it rotates to a final stationary position. However if the composable first appears in an on state, the animation will not start. How should I handle this?

Why when I navigate from screen A to screen B, screen A still recomposes? For example

composable(A){
   // other stuff
   ScreenA( navHostController, ..., onNavigateToB = { navHostController.navigate(B) } ) 
   // after onNavigateToB executes, it recomposes and re-renders ScreenA 
}
composable(B){
   ScreenB( ... )
}

Hello everyone, I have a suggestion to ask you regarding LazyColumn and nested lists. Nested scrollable is not allowed, but what if I wanted to have a list of cards (probably 10) where each one has an expanded collapse state that shows / hides an internal list? For example, in this codelab each card has the behaviour I am looking for, but it shows / hides a simple composable. A solution is adding an internal column but would it impact the performance if there are a lot of items? Another idea was using item (for the header) and items when expanded, but I am not sure if I can surround them with a card since we are in the LazyListScope which is not composable. Thanks!

How can I make editing a text field use incognito mode on the keyboard? similar to how it works on chrome incognito mode. KeyboardOptions doesn't look like it has an option, is it not supported?

Using AnimatedContent, can I somehow get the exiting content to overlap the entering content? instead of the opposite

Hi guys, I found a project that uses compose on the web directly without DOM API. https://github.com/mykola-dev/Tetris Where can I find docs showing how to do the same? Im unable to figure out what mykola-dev exactly do to make compose work on the web

I'm using

LazyLayoutPrefetchState

in a custom

LazyLayout

to prefetch the previous page and the next one (e.g. in "A, B, C, D, E", I prefetch A and C). However, pages can be swapped (e.g. "A, B, E, C, D"). How can I handle such thing? How can I tell the

Prefetcher

the item at index 2 has changed? Is

LazyLayoutItemProvider

involved at all?

Stupid question and very basic probably. When I navigate from screen A to screen B I can still get back to screen A even if I use

inclusive=true

. Code in 🧵

What is the term called for items in a LazyLayout(LazyRow/LazyColumn) which are not needed? For example, you have a long list where you have items which are

visible

, which may be shown imminently (

prefetched

), and items down the line which are far away in the list. Which state the last items are in?

I want to trigger a callback when a

LazyColumn

item becomes visible for only once. It shouldn't trigger if a user moves up and down the list. The problem I am facing is that irrespective of which side effect I use any time a Composable from down the list becomes visible, it seems, starts a new composition which means the side effect gets triggered when a user moves up or down the list. Is there a way to avoid this situation? I had asked my question here on SO. So far, the only way to handle this situation for me would be holding a variable in the data class (

isSeen: Boolean

).

I uploaded my first jetpack compose app and I’m getting a lot of crashes that I can’t reproduce on my devices.

Caused by java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.View android.view.ViewGroup.getChildAt(int)' on a null object reference
at androidx.activity.compose.ComponentActivityKt.setContent (ComponentActivityKt.java:264)
  at com.censored.censored.presentation.MainActivity.onCreate (MainActivity.java:264)

Full crash in thread -> MainActivity line 264 points to a DrawerItem: (first line is 264)

DrawerItem(
    imageDrawable = R.drawable.gold,
    title = "Text"
) {
    uriHandler.openUri("<https://google.com>")

}

Someone has an idea how I can fix it?

How can I make my navigation bar go off screen when scrolling similar to how top app bar has it?

I have a LazyRow, how can I make the items kind of like a stack, where at the start its a little overlap and at the end its more overlap

Hey Guys, Any idea on how to change text colour without recomposing the composable? Think google put out an example to use drawBehind to change the background. Since differing font colour change until the draw phase is not there(At least that I know of). Any directions on this?

Hello ! I have a

NavigationBar

in my Compose code, and I’m trying to have a navigation stack for each tab (so that when I change tabs, my stack for that tab is restored). What I have seen in the docs is that this all feature is build around routes. And my problem is, some tabs of the bottom bar have the same route showing different data. Are you aware of any way to make this a bit more dynamic ? Thanks for your help !

Hi! I have an issue with BottomSheetDialogFragment() - when I try to set it’s view as Jetpack Compose then I’m not able to set the necessary theme to the fragment by using

getTheme

function in the fragment which is working in other places in the app where .xml is being used. How can I get rounded bottom sheet corners in this situation?

Is it possible to apply more than one

horizontalArrangement

to the children of a

Row

. I want to use a combination of

Arrangement.spacedBy()

and

Arrangement.Center

to center the children in the row with even spacing. I can only do one at the moment.

This message was deleted.

Hi, How can I use

elevation

in

TopAppBar

of Material3? Thanks.

Hi, does it make any sense to try to implement sth like:

@Composable
fun <T> delayedStateOf(init: T, delayMs: Long = 200, calculation: () -> T): State<T> {
    ....
    val derived = derivedStateOf { if(someCacheNotOutdated) useCache else calculation()... } // FIXME: correct conditional control of reads (subscriptions)
    ....
    return derived
}

So this

delayedStateOf

would be a bit lazy updating, so I can use it as input for some low priority part of UI. Maybe better idea would be to use

SnapshotStateObserver

directly - I experimented with it a bit, but I have other issues with that Or maybe only reasonable solution is to go even lower level and play with snapshots directly? (like

snapshotFlow

does)

Really happy about the introduction of BOM in Compose. Seems like a no-brainer feature for everyone to use - https://developer.android.com/jetpack/compose/setup#using-the-bom

Are

LocalLifecycleOwner.current

and

LocalSavedStateRegistryOwner.current

guaranteed to be

Activity

?