如何在 Jetpack Compose Canvas 中绘制圆角多边形？

Question

我正在尝试使用 Jetpack Compose 中的 Canvas 创建一个圆角三角形。

我尝试使用此代码绘制三角形：

@Composable
fun RoundedTriangle() {
    Canvas(modifier = Modifier.size(500.dp)) {
        val trianglePath = Path().apply {
            val height = size.height
            val width = size.width
            moveTo(width / 2.0f, 0f)
            lineTo(width, height)
            lineTo(0f, height)
        }
            drawPath(trianglePath, color = Color.Blue)
    }
}

但是我不知道怎么把三角形的角弄圆。我也尝试过使用arcTo，但我无法得到合适的结果。

如何画出下图这样的东西？

Answer 1

对于 Stroke 你可以像这样指定舍入：

drawPath(
    ...
    style = Stroke(
        width = 2.dp.toPx(),
        pathEffect = PathEffect.cornerPathEffect(4.dp.toPx())
    )
)

然而 Fill 似乎缺少支持四舍五入。我创建了一个feature request，请给它加注星标。

但是Canvas有drawOutline函数，它接受Outline，它可以包装一个Path，和Paint，你可以指定pathEffect:

Canvas(modifier = Modifier.fillMaxWidth().aspectRatio(1f)) {
    val rect = Rect(Offset.Zero, size)
    val trianglePath = Path().apply {
        moveTo(rect.topCenter)
        lineTo(rect.bottomRight)
        lineTo(rect.bottomLeft)
        close()
    }

    drawIntoCanvas { canvas ->
        canvas.drawOutline(
            outline = Outline.Generic(trianglePath),
            paint = Paint().apply {
                color = Color.Black
                pathEffect = PathEffect.cornerPathEffect(rect.maxDimension / 3)
            }
        )
    }
}

Path 帮手：

fun Path.moveTo(offset: Offset) = moveTo(offset.x, offset.y)
fun Path.lineTo(offset: Offset) = lineTo(offset.x, offset.y)

结果：

Answer 2

基于@philip-dukhov 的回答，如果有人有兴趣将其应用于正方形

@Composable
fun SquirclePath(
    modifier: Modifier,
    smoothingFactor: Int = 60,
    color: Color,
    strokeWidth: Float,
) {
    Canvas(
        modifier = modifier
    ) {
        val rect = Rect(Offset.Zero, size)
        val percent = smoothingFactor.percentOf(rect.minDimension)
        val squirclePath = Path().apply {
            with(rect) {
                lineTo(topRight)
                lineTo(bottomRight)
                lineTo(bottomLeft)
                lineTo(topLeft)
                // this is where the path is finally linked together
                close()
            }
        }

        drawIntoCanvas { canvas ->
            canvas.drawOutline(
                outline = Outline.Generic(squirclePath),
                paint = Paint().apply {
                    this.color = color
                    this.style = PaintingStyle.Fill
                    this.strokeWidth = strokeWidth
                    pathEffect = PathEffect.cornerPathEffect(percent)
                }
            )
        }
    }
}

fun Int.percentOf(target:Float) = (this.toFloat() / 100) * target

如何在 Jetpack Compose Canvas 中绘制圆角多边形？

How to draw rounded corner polygons in Jetpack Compose Canvas?

android

kotlin

canvas

android-jetpack-compose

rounded-corners