Create a list of Reference for FocusRequester in Jetpack compose

Question

I have something like

            promotions.forEachIndexed { index, item ->
                key(item.hashCode()) {
                    PromotionItem(
                        promotionItem = item,
                        onRemove = { onRemove(index) }
                    )
                }
            }

I want to focus to one of them. I know I can create focusrequester like

val (item1, item2, item3, item4) = remember { FocusRequester.createRefs() }

How can I create the list of reference for the list in the code above. Or is there other way to handle the list?

Thanks in advance

Answer 1

First of all

val (item1, item2, item3, item4) = remember { FocusRequester.createRefs() }

This line returns only 16 FocusRequester objects most as

  @ExperimentalComposeUiApi
        object FocusRequesterFactory {
            operator fun component1() = FocusRequester()
            operator fun component2() = FocusRequester()
            operator fun component3() = FocusRequester()
            operator fun component4() = FocusRequester()
            operator fun component5() = FocusRequester()
            operator fun component6() = FocusRequester()
            operator fun component7() = FocusRequester()
            operator fun component8() = FocusRequester()
            operator fun component9() = FocusRequester()
            operator fun component10() = FocusRequester()
            operator fun component11() = FocusRequester()
            operator fun component12() = FocusRequester()
            operator fun component13() = FocusRequester()
            operator fun component14() = FocusRequester()
            operator fun component15() = FocusRequester()
            operator fun component16() = FocusRequester()
        }

First and complicated way is to use kotlin-reflection to get these components and put them inside a map or list of wrapper class instance

I add first alternative since it's part of the question but you can simply call put(promotion, FocusRequester())

@OptIn(ExperimentalComposeUiApi::class)
@Preview
@Composable
private fun FocusTest() {
    
    val focusRequesterFactory = remember { FocusRequester.createRefs() }

    val promotions = List(5) {
        Promotion(it)
    }

    val promotionMap = remember {
        linkedMapOf<Promotion, FocusRequester>().apply {

            val kCallables = focusRequesterFactory::class.members.toList()

            promotions.forEachIndexed { index, promotion ->

                (kCallables.getOrNull(index)
                    ?.call(focusRequesterFactory) as? FocusRequester)
                    ?.let { focusRequester ->
                        put(promotion, focusRequester)
                    }


                // Alternative 2
//                put(promotion, FocusRequester())

            }
        }
    }
    
    Column {
        promotionMap.forEach { (promotion, focusRequester) ->  
            
            // Do something
        }
    }
}

data class Promotion(val code: Int, val tag: String = "Promotion #$code")

Reflection api also requires you to add

implementation "org.jetbrains.kotlin:kotlin-reflect:1.8.21"

dependency