ComposeCustomLayoutDemo.kt

class PlaygroundActivity : ComponentActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContent {
            Layout(
                modifier = Modifier.fillMaxSize(),
                content = {
                    Box(
                        modifier = Modifier
                            .layoutId("green")
                            .size(100.dp)
                            .background(color = Color.Green)
                    )
                    Box(
                        modifier = Modifier
                            .layoutId("red")
                            .size(100.dp)
                            .background(color = Color.Red)
                    )
                    Box(
                        modifier = Modifier
                            .layoutId("blue")
                            .size(100.dp)
                            .background(color = Color.Blue)
                    )
                },
                measurePolicy = { measurables: List<Measurable>, constraints: Constraints ->
                    val looseConstaints = constraints.copy(
                        minHeight = 150.dp.roundToPx(),
                        minWidth = 100.dp.roundToPx(),
                    )

                    val blueMeasurable = measurables.find { it.layoutId == "blue" }!!
                    val greenMeasurable = measurables.find { it.layoutId == "green" }!!
                    val redMeasurable = measurables.find { it.layoutId == "red" }!!

                    val bluePlaceable = blueMeasurable.measure(looseConstaints)
                    val redPlaceable = redMeasurable.measure(looseConstaints)
                    val greenPlaceable = greenMeasurable.measure(looseConstaints)

                    layout(width = constraints.minWidth, height = constraints.minHeight) {
                        val y = 100
                        bluePlaceable.place(x = 100, y = y)
                        redPlaceable.place(x = 100, y = y + bluePlaceable.height)
                        greenPlaceable.place(x = 100, y = y + bluePlaceable.height + redPlaceable.height)
                    }
                },
            )
        }
    }
}