Currently in Jetpack Compose, this code throws an IllegalStateException because you cannot nest two vertically scrolling Composables:

@ExperimentalFoundationApi
@Composable
fun MyLazyColumn() {
    LazyColumn {
        item {
            Text(text = "My LazyColumn Title")
        }
        item {
            LazyVerticalGrid(cells = GridCells.Fixed(4)) {
                items(10) {
                    Box(
                        modifier = Modifier
                            .size(50.dp)
                            .padding(5.dp)
                            .background(Color.Gray)
                    )
                }
            }
        }
    }
}

I do not want the grid itself to scroll, but simply display a fixed grid of the Composable that I pass into it. Is there any workaround to displaying a non-scrolling grid inside a LazyColumn?

CodePudding user response：

LazyVerticalGrid with fixed cells count has pretty simple layout inside, based on LazyColumn plus Row.

Instead you can implement gridItems to be used with LazyColumn:

fun LazyListScope.gridItems(
    count: Int,
    nColumns: Int,
    horizontalArrangement: Arrangement.Horizontal = Arrangement.Start,
    itemContent: @Composable BoxScope.(Int) -> Unit,
) {
    gridItems(
        data = List(count) { it },
        nColumns = nColumns,
        horizontalArrangement = horizontalArrangement,
        itemContent = itemContent,
    )
}

fun <T> LazyListScope.gridItems(
    data: List<T>,
    nColumns: Int,
    horizontalArrangement: Arrangement.Horizontal = Arrangement.Start,
    itemContent: @Composable BoxScope.(T) -> Unit,
) {
    val rows = if (data.count() == 0) 0 else 1   (data.count() - 1) / nColumns
    items(rows) { rowIndex ->
        Row(horizontalArrangement = horizontalArrangement) {
            for (columnIndex in 0 until nColumns) {
                val itemIndex = rowIndex * nColumns   columnIndex
                if (itemIndex < data.count()) {
                    Box(
                        modifier = Modifier.weight(1f, fill = true),
                        propagateMinConstraints = true
                    ) {
                        itemContent.invoke(this, data[itemIndex])
                    }
                } else {
                    Spacer(Modifier.weight(1f, fill = true))
                }
            }
        }
    }
}

Usage:

LazyColumn {
    item {
        Text(text = "My LazyColumn Title")
    }
    // with count
    gridItems(10, nColumns = 4) { index -> 
        Box(
            modifier = Modifier
                .size(50.dp)
                .padding(5.dp)
                .background(Color.Gray)
        )
    }
    // or with list of items
    gridItems(listOf(1,2,3), nColumns = 4) { item ->
        Box(
            modifier = Modifier
                .size(50.dp)
                .padding(5.dp)
                .background(Color.Gray)
        )
    }
}