为什么以下代码段中的usort函数不仅按'num'键的值降序对矩阵进行排序，而且还对按'num'键值相等的元素按对值进行排序“ lett”键按升序排列？如何仅按函数体中给出的字母排序？
class AppleWatchLayoutManager : RecyclerView.LayoutManager() {
private val viewCache = SparseArray<View>()
override fun generateDefaultLayoutParams() = RecyclerView.LayoutParams(RecyclerView.LayoutParams.WRAP_CONTENT,
RecyclerView.LayoutParams.WRAP_CONTENT)
override fun onLayoutChildren(recycler: RecyclerView.Recycler, state: RecyclerView.State) {
detachAndScrapAttachedViews(recycler)
fill(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)
offsetChildrenVertical(-delta)
return delta
}
override fun scrollHorizontallyBy(dx: Int, recycler: RecyclerView.Recycler, state: RecyclerView.State): Int {
val delta = scrollHorizontallyInternal(dx)
offsetChildrenHorizontal(-delta)
return delta
}
private fun fill(recycler: RecyclerView.Recycler) {
val anchorView = findAchorView()
viewCache.clear()
val childCount = childCount
for (i in 0 until childCount) {
val view = getChildAt(i)
if (view != null) {
val position = getPosition(view)
viewCache.put(position, view)
}
}
var cacheSize = viewCache.size()
for (i in 0 until cacheSize) {
detachView(viewCache.valueAt(i))
}
fill(recycler, anchorView)
cacheSize = viewCache.size()
for (i in 0 until cacheSize) {
recycler.recycleView(viewCache.valueAt(i))
}
}
private fun fill(recycler: RecyclerView.Recycler, anchorView: View?) {
val anchorPosition = if (anchorView != null) getPosition(anchorView) else 0
val xOffset = if (anchorView != null) {
getDecoratedLeft(anchorView) + (getDecoratedMeasuredWidth(anchorView) / 2) - (width / 2)
} else {
0
}
val yOffset = if (anchorView != null) {
getDecoratedTop(anchorView) + (getDecoratedMeasuredHeight(anchorView) / 2) - (height / 2)
} else {
0
}
var filling = true
var round = 0
var position = anchorPosition
var scale = 0.9f
while (filling && position < itemCount) {
val sector = if (round == 0) 0.0 else 2 * PI / (6 * round)
var angle = 0.0
if (round == 0) {
filling = fillRound(recycler, round, position, angle, xOffset, yOffset, 1f)
position++
} else {
for (i in 1..(6 * round)) {
filling = filling && fillRound(recycler, round, position, angle, xOffset, yOffset, scale)
angle += sector
position++
}
}
round++
scale -= 0.1f
}
}
private fun scrollHorizontallyInternal(dx: Int): Int {
if (childCount == 0) {
return 0
}
val currentRound = getCurrentRound()
val roundsCount = getRoundsCount()
if (currentRound == roundsCount) {
val mostLeftChild = findMostLeftChild()
val mostRightChild = findMostRightChild()
if (mostLeftChild != null && mostRightChild != null) {
val viewSpan = getDecoratedRight(mostRightChild) - getDecoratedLeft(mostLeftChild)
if (viewSpan <= width) {
return 0
}
} else {
return 0
}
}
var delta = 0
if (dx < 0) {
val mostLeftChild = findMostLeftChild()
delta = if (mostLeftChild != null) {
Math.max(getDecoratedLeft(mostLeftChild), dx)
} else dx
} else if (dx > 0) {
val mostRightChild = findMostRightChild()
delta = if (mostRightChild != null) {
Math.min(getDecoratedRight(mostRightChild) - width, dx)
} else dx
}
return delta
}
private fun scrollVerticallyInternal(dy: Int): Int {
if (childCount == 0) {
return 0
}
// All views fit on screen
if (childCount == itemCount) {
val highestChild = findHighestChild()
val lowestChild = findLowestChild()
if (highestChild != null && lowestChild != null) {
val viewSpan = getDecoratedBottom(lowestChild) - getDecoratedTop(highestChild)
if (viewSpan <= height) {
return 0
}
} else {
return 0
}
}
var delta = 0
// content moves down
if (dy < 0) {
val highestChild = findHighestChild()
delta = if (highestChild != null) {
Math.max(getDecoratedTop(highestChild), dy)
} else dy
} else if (dy > 0) {
val lowestChild = findLowestChild()
delta = if (lowestChild != null) {
Math.min(getDecoratedBottom(lowestChild) - height, dy)
} else dy
}
return delta
}
private fun fillRound(recycler: RecyclerView.Recycler, round: Int, element: Int, angle: Double,
xOffset: Int, yOffset: Int, scale: Float): Boolean {
var view = viewCache[element]
if (view == null) {
view = recycler.getViewForPosition(element)
addView(view)
measureChildWithMargins(view, 0, 0)
val x = getDecoratedMeasuredWidth(view) * round * Math.cos(angle) + width / 2 + xOffset
val y = getDecoratedMeasuredHeight(view) * round * Math.sin(angle) + height / 2 + yOffset
val left = (x - getDecoratedMeasuredWidth(view) / 2).toInt()
val top = (y - getDecoratedMeasuredHeight(view) / 2).toInt()
val right = (x + getDecoratedMeasuredWidth(view) / 2).toInt()
val bottom = (y + getDecoratedMeasuredHeight(view) / 2).toInt()
layoutDecorated(view, left, top, right, bottom)
} else {
attachView(view)
viewCache.remove(element)
}
val decoratedBottom = getDecoratedBottom(view)
val decoratedTop = getDecoratedTop(view)
val decoratedLeft = getDecoratedLeft(view)
val decoratedRight = getDecoratedRight(view)
return (decoratedBottom <= height && decoratedTop >= 0) ||
(decoratedLeft >= 0 && decoratedRight <= width)
}
private fun getRoundsCount(): Int {
var itemCount = itemCount
var rounds = 0
var coeff = 1
while (itemCount > 0) {
rounds++
itemCount -= 6 * coeff
coeff++
}
return rounds
}
private fun getRoundByPosittion(position: Int): Int {
if (position == 0) {
return 0
}
if (position >= itemCount) {
throw IndexOutOfBoundsException("There's less items in RecyclerView than given position. Position is $position")
}
var elementsCount = 1
var round = 0
var coeff = 1
do {
round++
elementsCount += 6 * coeff
coeff++
} while (position > elementsCount)
return round
}
private fun getCurrentRound(): Int {
var childCount = childCount
if (childCount <= 1) {
return 0
} else if (childCount <= 7) {
return 1
}
childCount --
var round = 1
var coeff = 1
while (childCount > 0) {
childCount -= 6 * coeff
coeff++
round++
}
return round
}
private fun findHighestChild(): View? {
val childCount = childCount
if (childCount > 0) {
var highestView = getChildAt(0)
for (i in 0 until childCount) {
val view = getChildAt(i)
if (view != null) {
val top = getDecoratedTop(view)
val highestViewTop = getDecoratedTop(highestView!!)
if (top < highestViewTop) {
highestView = view
}
}
}
return highestView
}
return null
}
private fun findLowestChild(): View? {
val childCount = childCount
if (childCount > 0) {
var lowestView = getChildAt(0)
for (i in 0 until childCount) {
val view = getChildAt(i)
if (view != null) {
val bottom = getDecoratedBottom(view)
val lowestViewBottom = getDecoratedBottom(lowestView!!)
if (bottom > lowestViewBottom) {
lowestView = view
}
}
}
return lowestView
}
return null
}
private fun findMostLeftChild(): View? {
val childCount = childCount
if (childCount > 0) {
var mostLeftView = getChildAt(0)
for (i in 0 until childCount) {
val view = getChildAt(i)
if (view != null) {
val left = getDecoratedLeft(view)
val mostLeftViewLeft = getDecoratedLeft(mostLeftView!!)
if (left < mostLeftViewLeft) {
mostLeftView = view
}
}
}
return mostLeftView
}
return null
}
private fun findMostRightChild(): View? {
val childCount = childCount
if (childCount > 0) {
var mostRightView = getChildAt(0)
for (i in 0 until childCount) {
val view = getChildAt(i)
if (view != null) {
val right = getDecoratedRight(view)
val mostRightViewRight = getDecoratedRight(mostRightView!!)
if (right > mostRightViewRight) {
mostRightView = view
}
}
}
return mostRightView
}
return null
}
private fun findAchorView(): View? {
val childCount = childCount
val centerX = width / 2
val centerY = height / 2
var anchorView: View? = null
var minDistance = Int.MAX_VALUE
for (i in 0 until childCount) {
val view = getChildAt(i)
if (view != null) {
val distance = distanceBetweenCenters(view, centerX, centerY)
if (distance < minDistance) {
minDistance = distance
anchorView = view
}
}
}
return anchorView
}
private fun distanceBetweenCenters(view: View, centerX: Int, centerY: Int): Int {
val viewCenterX = getDecoratedLeft(view) + getDecoratedMeasuredWidth(view) / 2
val viewCenterY = getDecoratedTop(view) + getDecoratedMeasuredHeight(view) / 2
return sqrt((centerX - viewCenterX) * (centerX - viewCenterX) * 1.0 + (centerY - viewCenterY) * (centerY - viewCenterY)).toInt()
}
}
答案 0 :(得分：1)
对数组进行排序将尝试对每个项目进行排序，因此即使这些项目相等，也不能强制usort（仅为您提供值）来维持项目的原始顺序。
但是，您可以利用uksort来访问键（也可以从原始数组中访问），从而回退到这一点：
uksort($mtx, function ($key1, $key2) use ($mtx) {
$a = $mtx[$key1];
$b = $mtx[$key2];
if ($a['num'] < $b['num']) {
return 1;
}
if ($a['num'] > $b['num']) {
return -1;
}
return $key1 - $key2;
});
缩略形式：
uksort($mtx, function ($key1, $key2) use ($mtx) {
return $mtx[$key2]['num'] - $mtx[$key1]['num'] ?: $key1 - $key2;
});