Wavy box in Jetpack compose

Question

Is there a way to make a box with a wavy top with Canvas?

I would like to know if this effect can be achieved directly with a Canvas, it is not necessary to have a scrolling animation.

Answer 1

It's not quite clear why you're talking about Canvas. To crop a view like this, you can use a custom Shape and apply it to your view with Modifier.clip. Here's a shape you can use:

class WavyShape(
    private val period: Dp,
    private val amplitude: Dp,
) : Shape {
    override fun createOutline(
        size: Size,
        layoutDirection: LayoutDirection,
        density: Density,
    ) = Outline.Generic(Path().apply {
        val wavyPath = Path().apply {
            val halfPeriod = with(density) { period.toPx() } / 2
            val amplitude = with(density) { amplitude.toPx() }
            moveTo(x = -halfPeriod / 2, y = amplitude)
            repeat(ceil(size.width / halfPeriod + 1).toInt()) { i ->
                relativeQuadraticBezierTo(
                    dx1 = halfPeriod / 2,
                    dy1 = 2 * amplitude * (if (i % 2 == 0) 1 else -1),
                    dx2 = halfPeriod,
                    dy2 = 0f,
                )
            }
            lineTo(size.width, size.height)
            lineTo(0f, size.height)
        }
        val boundsPath = Path().apply {
            addRect(Rect(offset = Offset.Zero, size = size))
        }
        op(wavyPath, boundsPath, PathOperation.Intersect)
    })
}

If you really need to use this inside Canvas for some reason, you can pass the same Path that I create inside WavyShape to DrawScope.clipPath, so that the contents of the clipPath block will be clipped.

Apply custom shape to your Image or any other view:

Image(
    painter = painterResource(id = R.drawable.my_image_1),
    contentDescription = null,
    contentScale = ContentScale.FillBounds,
    modifier = Modifier
        .clip(WavyShape(period = 100.dp, amplitude = 50.dp))
)

Result: