Наконец-то у меня есть решение.Перед размещением элементов я просто определяю коллекцию специальных моделей, которая содержит информацию о ее положении на экране.Затем во время прокрутки я изменяю коллекцию, выкладываю элементы, которые сейчас на экране, и перерабатываю элементы, которых нет на экране.Но есть недостаток: я должен передать размер элемента конструктору менеджера, чтобы обеспечить правильное заполнение дочерних элементов.itemSize должно быть таким же, как определено в XML элемента.Возможно, решение не идеальное, но у меня оно работает нормально.Вот код LayoutManager.
class BubbleLayoutManager(private val itemSize: Int) : RecyclerView.LayoutManager() {
private val children = mutableListOf<Child>()
override fun generateDefaultLayoutParams() = RecyclerView.LayoutParams(RecyclerView.LayoutParams.WRAP_CONTENT,
RecyclerView.LayoutParams.WRAP_CONTENT)
override fun onLayoutChildren(recycler: RecyclerView.Recycler, state: RecyclerView.State) {
fillChildren()
detachAndScrapAttachedViews(recycler)
fillView(recycler)
}
override fun canScrollVertically() = true
override fun canScrollHorizontally() = true
override fun scrollVerticallyBy(dy: Int, recycler: RecyclerView.Recycler, state: RecyclerView.State): Int {
val delta = scrollVerticallyInternal(dy)
offsetChildren(yOffset = -delta)
offsetChildrenVertical(-delta)
fillAndRecycle(recycler)
return dy
}
override fun scrollHorizontallyBy(dx: Int, recycler: RecyclerView.Recycler, state: RecyclerView.State): Int {
val delta = scrollHorizontallyInternal(dx)
offsetChildren(xOffset = -delta)
offsetChildrenHorizontal(-delta)
fillAndRecycle(recycler)
return dx
}
private fun fillAndRecycle(recycler: RecyclerView.Recycler) {
val itemCount = itemCount
for (i in 0 until itemCount) {
if (i < children.size) {
val child = children[i]
val childRect = childRect(child)
val alreadyDrawn = alreadyDrawn(child)
if (!alreadyDrawn && fitOnScreen(childRect)) {
val view = recycler.getViewForPosition(i)
addView(view)
measureChildWithMargins(view, 0, 0)
layoutDecorated(view, childRect.left, childRect.top, childRect.right, childRect.bottom)
}
}
}
recycleViews(recycler)
updateScales()
}
private fun recycleViews(recycler: RecyclerView.Recycler) {
val childCount = childCount
for (i in 0 until childCount) {
val view = getChildAt(i)
if (view != null && !fitOnScreen(view)) {
detachView(view)
recycler.recycleView(view)
}
}
}
private fun fillView(recycler: RecyclerView.Recycler) {
val itemCount = itemCount
for (i in 0 until itemCount) {
if (i < children.size) {
val childRect = childRect(children[i])
if (fitOnScreen(childRect)) {
val view = recycler.getViewForPosition(i)
addView(view)
measureChildWithMargins(view, 0, 0)
layoutDecorated(view, childRect.left, childRect.top, childRect.right, childRect.bottom)
}
}
}
updateScales()
}
private fun scrollVerticallyInternal(dy: Int): Int {
if (childCount == 0) {
return 0
}
val highestChild = children.minBy { it.y }
val lowestChild = children.maxBy { it.y }
if (highestChild != null && lowestChild != null) {
if (lowestChild.y + itemSize / 2 <= height && highestChild.y - itemSize / 2 >= 0) {
return 0
}
} else {
return 0
}
var delta = 0
if (dy < 0) {
delta = if (highestChild.y - itemSize / 2 < 0) {
max(highestChild.y - itemSize / 2, dy)
} else 0
} else if (dy > 0) {
delta = if (lowestChild.y + itemSize / 2 > height) {
min(lowestChild.y + itemSize / 2 - height, dy)
} else 0
}
return delta
}
private fun scrollHorizontallyInternal(dx: Int): Int {
if (childCount == 0) {
return 0
}
val mostLeftChild = children.minBy { it.x }
val mostRightChild = children.maxBy { it.x }
if (mostLeftChild != null && mostRightChild != null) {
if (mostLeftChild.x - itemSize / 2 >= 0 && mostRightChild.x + itemSize / 2 <= width) {
return 0
}
} else {
return 0
}
var delta = 0
if (dx < 0) {
delta = if (mostLeftChild.x - itemSize / 2 < 0) {
max(mostLeftChild.x - itemSize / 2, dx)
} else 0
} else if (dx > 0) {
delta = if (mostRightChild.x + itemSize / 2 > width) {
min(mostRightChild.x + itemSize / 2 - width, dx)
} else 0
}
return delta
}
private fun offsetChildren(xOffset: Int = 0, yOffset: Int = 0) {
children.forEach { it.offset(xOffset, yOffset) }
}
private fun updateScales() {
val centerX = width / 2
val centerY = height / 2
val distanceMap = sortedMapOf<Int, MutableList<Int>>()
val childCount = childCount
for (i in 0 until childCount) {
val view = getChildAt(i)
if (view != null) {
val distance = distance(centerX, centerY, view.x.toInt() + view.width / 2, view.y.toInt() + view.height / 2)
val positions = distanceMap.getOrPut(distance) { mutableListOf() }
positions.add(i)
}
}
var scale = 1f
distanceMap.keys.forEach { key ->
val positions = distanceMap[key]
if (positions != null) {
for (position in positions) {
val view = getChildAt(position)
if (view != null) {
view.scaleX = scale
view.scaleY = scale
}
}
}
scale *= 0.95f
}
}
private fun distance(x1: Int, y1: Int, x2: Int, y2: Int) = sqrt(((x2 - x1) * (x2 - x1)).toFloat() + ((y2 - y1) * (y2 - y1)).toFloat()).toInt()
private fun childRect(child: Child): Rect {
val left = child.x - itemSize / 2
val top = child.y - itemSize / 2
val right = left + itemSize
val bottom = top + itemSize
return Rect(left, top, right, bottom)
}
private fun fillChildren() {
children.clear()
val centerX = width / 2
val centerY = height / 2
val itemCount = itemCount
if (itemCount > 0) {
children.add(Child(centerX, centerY))
if (itemCount > 1) {
for (i in 1 until itemCount) {
fillChildrenRelative(children[i - 1], itemCount)
}
}
}
}
private fun fillChildrenRelative(anchorChild: Child, itemCount: Int) {
var i = 0
var direction = Direction.initial()
while (i < 4 && children.size < itemCount) {
val childX = anchorChild.x + (itemSize / 2) * direction.widthMultiplier
val childY = anchorChild.y + itemSize * direction.heightMultiplier
if (!hasChild(childX, childY)) {
children.add(Child(childX, childY))
}
direction = direction.next()
i++
}
}
private fun hasChild(x: Int, y: Int) = children.any { it.x == x && it.y == y }
private fun fitOnScreen(view: View) = fitOnScreen(getViewRect(view))
private fun getViewRect(view: View) = Rect(
getDecoratedLeft(view),
getDecoratedTop(view),
getDecoratedRight(view),
getDecoratedBottom(view)
)
private fun fitOnScreen(rect: Rect): Boolean = rect.intersects(0, 0, width, height)
private fun alreadyDrawn(child: Child): Boolean {
val rect = childRect(child)
val childCount = childCount
for (i in 0 until childCount) {
val view = getChildAt(i)
if (view != null) {
val viewRect = getViewRect(view)
if (viewRect.intersects(rect.left, rect.top, rect.right, rect.bottom)) {
return true
}
}
}
return false
}
private data class Child(
var x: Int,
var y: Int
) {
fun offset(xOffset: Int = 0, yOffset: Int = 0) {
x += xOffset
y += yOffset
}
}
}
// Direction.kt
internal sealed class Direction(
val widthMultiplier: Int, val heightMultiplier: Int
) {
companion object {
internal fun initial(): Direction = LeftTop
}
}
internal object LeftTop : Direction(-1, -1)
internal object RightTop : Direction(1, -1)
internal object LeftBottom : Direction(-1, 1)
internal object RightBottom : Direction(1, 1)
internal fun Direction.next() = when (this) {
is LeftTop -> RightTop
is RightTop -> LeftBottom
is LeftBottom -> RightBottom
is RightBottom -> LeftTop
}