如何在布局中添加可组合

Question

我目前正在编写自定义布局； 因此，我使用的是Layout Composable。

Layout(
    modifier = modifier,
    content = content
) { measurables, constraints ->

// Measure my measurables and place my placeables using layout
}}

现在我想使用Canvas使用先前计算的可放置对象 x,y 的位置计算进行绘制。

我不能添加Canvas因为可组合只能在可组合内调用。

知道我会怎么做吗？

Answer 1

在这种情况下，您可以使用SubcomposeLayout ，如下所示：

SubcomposeLayout { constraints ->
    val contentMeasurables = subcompose(slotId = "content", content = content)
    val contentPlaceables = contentMeasurables.map { it.measure(constraints) }
    val canvasPlaceable = subcompose(slotId = "canvas") {
        Canvas(Modifier) {
            // draw using contentPlaceables
        }
    // when you now that you only have added a single view inside subcompose, 
    // you can take [0] from subcompose result
    // otherwise you also can use map as with content
    }[0].measure(constraints)
    layout(/*...*/)
}