Android 是否可以附加事件处理程序，如onClick，拖动到Canvas Composable中绘制的内容，或使用drawBehind修饰符

不能将修改器指定给在画布中绘制的内容(Spacer with Modifier.drawBehind)或在绘制修改器中绘制的其他图形.

但您可以将 node 的位置、半径、Angular 和其他视觉属性存储在数据类中，并使用这些类中的值绘制它们.当用户与任何 node 交互时，您将更新这些属性，而读取这些属性的画布将正确绘制您的 node 树.

如果你想检测被touch 的形状是圆的，很容易根据到中心的距离来检测，但如果你想的话，你也可以使用路径.

我发布了一个在屏幕上随机绘制圆圈的示例，因为我没有数据 struct 来绘制 node ，但它应该给出一个如何实现它的 idea .

@Preview
@Composable
private fun Test() {

    val drawList = remember {
        mutableStateListOf<DrawProperties>()
    }

    var touchIndex by remember {
        mutableStateOf(-1)
    }

    LaunchedEffect(Unit) {
        repeat(5) {
            val properties = DrawProperties(
                center = Offset(
                    Random.nextInt(100, 1000).toFloat(),
                    Random.nextInt(100, 1500).toFloat()
                )
            )

            drawList.add(properties)
        }
    }

    Canvas(
        modifier = Modifier.fillMaxSize()
            .pointerInput(Unit) {
                detectDragGestures(
                    onDragStart = { offset ->
                        touchIndex = -1
                        drawList.forEachIndexed { index, drawProperties ->
                            val isTouched =
                                isTouched(drawProperties.center, offset, drawProperties.radius)

                            if (isTouched) {
                                touchIndex = index
                            }
                        }
                    },
                    onDrag = { change, dragAmount: Offset ->
                        val item = drawList.getOrNull(touchIndex)
                        item?.let { drawItem ->
                            drawList[touchIndex] = drawItem.copy(
                                center = drawItem.center.plus(dragAmount),
                                color = Color.Green
                            )
                        }
                    },
                    onDragEnd = {
                        val item = drawList.getOrNull(touchIndex)
                        item?.let { drawItem ->
                            drawList[touchIndex] = drawItem.copy(
                                color = Color.Red
                            )
                        }
                    }
                )
            }
    ) {
        drawList.forEachIndexed { index, drawProperties ->

            if (touchIndex != index) {
                drawCircle(
                    color = drawProperties.color,
                    center = drawProperties.center,
                    radius = drawProperties.radius
                )
            }
        }

        if (touchIndex > -1) {
            drawList.getOrNull(touchIndex)?.let { drawProperties ->
                drawCircle(
                    color = drawProperties.color,
                    center = drawProperties.center,
                    radius = drawProperties.radius
                )
            }
        }
    }

}

private fun isTouched(center: Offset, touchPosition: Offset, radius: Float): Boolean {
    return center.minus(touchPosition).getDistanceSquared() < radius * radius
}

data class DrawProperties(
    val center: Offset,
    val radius: Float = 80f,
    val color: Color = Color.Red
)