testivanivan's questions

我有 Row 带有 .horizo​​ntalScroll()，我需要弹跳动画效果。也就是说，当列表出现时，它会向前滚动一点，然后返回。同时，我需要在返回滚动时使用弹簧效果。这是我的实现：

val scrollState = rememberScrollState()
val coroutineScope = rememberCoroutineScope()
val bounceDistance = 150
    
LaunchedEffect(Unit) {
    val animatable = Animatable(scrollState.value.toFloat())

    coroutineScope.launch {
        animatable.animateTo(
            targetValue = bounceDistance.toFloat(),
            animationSpec = tween(
                durationMillis = 200,
                easing = LinearOutSlowInEasing
            )
        )
        scrollState.scrollTo(animatable.value.toInt())
        animatable.animateTo(
            targetValue = 0f,
            animationSpec = spring(
                dampingRatio = 0.4f,
                stiffness = Spring.StiffnessLow
            )
        )
        scrollState.scrollTo(animatable.value.toInt())
        animatable.animateTo(
            targetValue = bounceDistance * 0.3f,
            animationSpec = tween(
                durationMillis = 400,
                easing = LinearOutSlowInEasing
            )
        )
        scrollState.scrollTo(animatable.value.toInt())
        animatable.animateTo(
            targetValue = 0f,
            animationSpec = spring(
                dampingRatio = 0.6f,
                stiffness = Spring.StiffnessLow
            )
        )

        scrollState.scrollTo(animatable.value.toInt())
    }
}

但是，一切看起来都很不顺利，而且很慢。我做错了什么？

PS 这是为了提示用户该组件具有水平滚动。

我正在尝试绘制带有各个部分的饼图并显示每个部分的标签。标签应显示在每个部分的开头，并与饼图保持 10dp 的间距。

这是我的代码：

@Composable
fun PieChartLocal(
    modifier: Modifier = Modifier,
    width: Float,
    thickness: Float,
    duration: Int,
    sections: List<Section>,
) {
    val sweepAngles = remember(sections) { findSweepAngles(sections) }
    val animateFloat = remember { Animatable(0f) }

    val density = LocalDensity.current
    val paddingDp = 18.dp
    val textSizeDp = 10.sp
    val paddingPx = with(density) { paddingDp.toPx() }

    val textSizePx = with(density) { textSizeDp.toPx() }

    LaunchedEffect(animateFloat) {
        animateFloat.animateTo(
            targetValue = 1f,
            animationSpec = tween(durationMillis = duration, easing = LinearEasing)
        )
    }

    Canvas(
        modifier = modifier
            .size((width + 2 * (paddingDp.value + textSizeDp.value)).dp)
    ) {
        var startAngle = 0f
        val radius =
            (size.minDimension - 2 * (paddingPx + textSizePx)) / 2
        val center = size.center

        for (i in sweepAngles.indices) {
            val sweepAngle = sweepAngles[i] * animateFloat.value
            val color = sections[i].color

            drawArc(
                color = color,
                startAngle = startAngle,
                sweepAngle = sweepAngle,
                useCenter = false,
                style = Stroke(width = thickness),
                topLeft = Offset(center.x - radius, center.y - radius),
                size = Size(radius * 2, radius * 2),
            )

            val angleInRadians = Math.toRadians(startAngle.toDouble())
            val textRadius = radius + paddingPx
            val x = center.x + textRadius * cos(angleInRadians).toFloat()
            val y = center.y + textRadius * sin(angleInRadians).toFloat()

            val percentage = (sweepAngles[i] / ROUND_ANGLE * 100).toInt()
            
            drawContext.canvas.nativeCanvas.apply {
                drawText(
                    "$percentage%",
                    x,
                    y,
                    TextPaint().apply {
                        textAlign = Paint.Align.CENTER
                        textSize = textSizePx
                    }
                )
            }

            startAngle += sweepAngle
        }
    }
}

private fun findSweepAngles(sections: List<Section>): List<Float> {
    val values = sections.map(Section::value)
    val sumValues = values.sum()
    return values.map { value -> ROUND_ANGLE * value / sumValues }
}

问题是，对于某些标签，我的饼图偏移量不正确。对于许多标签，它等于预期的 10dp，而对于其余标签，它完全不存在。可能是什么问题？

请帮我..

我正在使用 kotlinx.Clock.now() 来获取当前日期。接下来我需要将此日期转换为 LocalDateTime，这是我的代码：

Clock.System.now().toLocalDateTime(TimeZone.currentSystemDefault())

效果很好。但是，我需要获取今天的日期，但恰好是今天的开始，即 00:00:00。是否可以将时间重置为 00:00:00？