Android Compose颜色选择器

代码来自这里

@Composable
fun ColorPicker(onColorSelected: (Color) -> Unit) {
    val screenWidth = LocalConfiguration.current.screenWidthDp.dp
    val screenWidthInPx = with(LocalDensity.current) { screenWidth.toPx() }
    var activeColor by remember { mutableStateOf(Red) }

    val max = screenWidth - 16.dp
    val min = 0.dp
    val (minPx, maxPx) = with(LocalDensity.current) { min.toPx() to max.toPx() }
    val dragOffset = remember { mutableStateOf(0f) }
    Box(modifier = Modifier.padding(8.dp)) {
        //slider
        Spacer(
            modifier = Modifier
                .height(10.dp)
                .fillMaxWidth()
                .clip(RoundedCornerShape(4.dp))
                .background(brush = colorMapGradient(screenWidthInPx))
                .align(Alignment.Center)
                .pointerInput("painter") {
                    detectTapGestures { offset ->
                        dragOffset.value = offset.x
                        activeColor = getActiveColor(dragOffset.value, screenWidthInPx)
                        onColorSelected.invoke(activeColor)
                    }
                }
        )
        // draggable icon
        Icon(
            imageVector = Icons.Filled.FiberManualRecord,
            tint = activeColor,
            contentDescription = null,
            modifier = Modifier
                .offset { IntOffset(dragOffset.value.roundToInt(), 0) }
                .border(
                    border = BorderStroke(4.dp, MaterialTheme.colors.onSurface),
                    shape = CircleShape
                )
                .draggable(
                    orientation = Orientation.Horizontal,
                    state = rememberDraggableState { delta ->
                        val newValue = dragOffset.value + delta
                        dragOffset.value = newValue.coerceIn(minPx, maxPx)
                        activeColor = getActiveColor(dragOffset.value, screenWidthInPx)
                        onColorSelected.invoke(activeColor)
                    }
                )
        )
    }
}

fun colorMapGradient(screenWidthInPx: Float) = Brush.horizontalGradient(
    colors = createColorMap(),
    startX = 0f,
    endX = screenWidthInPx
)

fun createColorMap(): List {
    val colorList = mutableListOf()
    for (i in 0..360 step (10)) {
        val randomSaturation = 90 + Random.nextFloat() * 10
        val randomLightness = 50 + Random.nextFloat() * 10
        val hsv = AndroidColor.HSVToColor(
            floatArrayOf(
                i.toFloat(),
                randomSaturation,
                randomLightness
            )
        )
        colorList.add(Color(hsv))
    }

    return colorList
}

fun getActiveColor(dragPosition: Float, screenWidth: Float): Color {
    val hue = (dragPosition / screenWidth) * 360f
    val randomSaturation = 90 + Random.nextFloat() * 10
    val randomLightness = 50 + Random.nextFloat() * 10
    return Color(
        AndroidColor.HSVToColor(
            floatArrayOf(
                hue,
                randomSaturation,
                randomLightness
            )
        )
    )
}