Hello everyone, i'm facing a problem with LazyVert...

# compose

[Lucca Beurmann]

Hello everyone, i'm facing a problem with LazyVerticalGrids that causes my app to crash. I'm using a LazyGrid to display a list of photos (receiving the image url from an api and loading in my view using Glide) that can be cleared whenever the user sends a request with a differente filter, but when the list is cleared my application crashes with an Index out Of Bounds Exception

[Danish Ansari]

You yourself pointed out the actual problem. It doesn't have anything to do LazyVerticalGrid. Wherever you're using your list just put some kind of isEmpty() or contains() check according to your need

[Lucca Beurmann]

I'm already doing this check, only displaying the list if it's not empty

if (photos.isEmpty()) {
    SearchPhotosEmpty(Modifier.align(Alignment.Center))
} else {
    SearchPhotosList(
        photos = photos,
        listState = listState,
        onLoadMorePhotos = loadMorePhotos,
        isPreview = isPreview,
        modifier = Modifier.fillMaxSize()
    )
}

[Chris Miller]

Just a guess - is your use of photos threadsafe? And does the LazyGrid know to recompose when the photos change?

[Lucca Beurmann]

I think i found the source of this weird behavior

[Lucca Beurmann]

I'm using a sealed class named ViewState to update my UI according to the proper view state of my screen. This class contains 4 differente types: Idle, Ready, Loading and Error

[Lucca Beurmann]

when (screenState) {
    is ViewState.Idle -> {
        Column(
            modifier = Modifier
                .fillMaxSize()
                .padding(horizontal = 20.dp),
            horizontalAlignment = Alignment.CenterHorizontally,
            verticalArrangement = Arrangement.Center
        ) {
            Icon(
                imageVector = Icons.Default.ImageSearch,
                contentDescription = null,
                modifier = Modifier
                    .size(60.dp)
                    .padding()
                    .padding(bottom = 10.dp),
                tint = MaterialTheme.colors.onBackground
            )
            Text(
                text = "Whoops nothing to see here yet, try to search for something cute like fluffy cats.",
                style = AppTypoGraph.roboto_bold().copy(
                    fontSize = 18.sp,
                    textAlign = TextAlign.Center
                )
            )
        }
    }
    is ViewState.Loading -> {
        Box(modifier = Modifier.fillMaxSize(), contentAlignment = Alignment.Center) {
            ProgressIndicator()
        }
    }
    is ViewState.Ready -> Box(Modifier.fillMaxSize()) {
        if (photos.isEmpty()) {
            SearchPhotosEmpty(Modifier.align(Alignment.Center))
        } else {
            SearchPhotosList(
                photos = photos,
                listState = listState,
                onLoadMorePhotos = loadMorePhotos,
                isPreview = isPreview,
                modifier = Modifier.fillMaxSize()
            )
            if (isMorePhotosLoading) MorePhotosLoader(
                modifier = Modifier
                    .align(Alignment.BottomCenter)
                    .padding()
                    .padding(20.dp)
                    .zIndex(1f)
            )
        }

    }
    is ViewState.Error -> Unit
}

I'm using a when statement to set the correct layout and for some reason this is why the exception is occurring

[Lucca Beurmann]

if i extract the LazyGrid of this when clausule and leave it unaware of the current view state it works as intended

[Lucca Beurmann]

I'm just trying to understand why this is happening

[Lucca Beurmann]

well actually this is not the cause of the problem

[Lucca Beurmann]

i was using the .clear() before doing the api call

[Lucca Beurmann]

i moved the clear() to the onSuccess method and it worked

[Lucca Beurmann]

don't know why tho

[Tobias Suchalla]

You're probably seeing this:
https://github.com/JetBrains/compose-jb/issues/1157
https://github.com/JetBrains/compose-jb/issues/1173

Build v1.0.0-alpha4-build331 was the last one without this issue.

[Andrey Kulikov]

please file a bug with the stacktrace. it shouldn’t crash