我有一个带有自定义UICollectionLayout的UICollectionView。一切正常，直到我尝试插入一行......
然后我收到以下错误，似乎无法弄清楚如何解决它。
*** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'no UICollectionViewLayoutAttributes instance for -layoutAttributesForItemAtIndexPath: <NSIndexPath: 0xc000000000000016> {length = 2, path = 0 - 0}'
*** First throw call stack:
(
0 CoreFoundation 0x000000010915ae65 __exceptionPreprocess + 165
1 libobjc.A.dylib 0x0000000108789deb objc_exception_throw + 48
2 CoreFoundation 0x000000010915acca +[NSException raise:format:arguments:] + 106
3 Foundation 0x000000010591a4de -[NSAssertionHandler handleFailureInMethod:object:file:lineNumber:description:] + 198
4 UIKit 0x00000001073e361c -[UICollectionViewData layoutAttributesForItemAtIndexPath:] + 627
5 UIKit 0x00000001073a2859 __51-[UICollectionView _viewAnimationsForCurrentUpdate]_block_invoke1541 + 176
6 UIKit 0x00000001073a02ed -[UICollectionView _viewAnimationsForCurrentUpdate] + 4524
7 UIKit 0x00000001073a4a5c __62-[UICollectionView _updateWithItems:tentativelyForReordering:]_block_invoke1611 + 197
8 UIKit 0x0000000106be01b8 +[UIView(Animation) performWithoutAnimation:] + 65
9 UIKit 0x00000001073a3e07 -[UICollectionView _updateWithItems:tentativelyForReordering:] + 3241
10 UIKit 0x000000010739eb98 -[UICollectionView _endItemAnimationsWithInvalidationContext:tentativelyForReordering:] + 15556
11 UIKit 0x00000001073a5ee7 -[UICollectionView _performBatchUpdates:completion:invalidationContext:tentativelyForReordering:] + 415
12 UIKit 0x00000001073a5d25 -[UICollectionView _performBatchUpdates:completion:invalidationContext:] + 74
13 UIKit 0x00000001073a5cc8 -[UICollectionView performBatchUpdates:completion:] + 53
14 Qanda 0x0000000103d9e0d9 _TFC5Qanda32HomeFeedCollectionViewController22redrawViewAfterNewDatafS0_FGSaCS_10QandaModel_T_ + 4105
15 Qanda 0x0000000103dad5ca _TFFFC5Qanda32HomeFeedCollectionViewController9fetchDataFS0_FT_T_U_FTGSqGSaCS_10QandaModel__Sb_T_U0_FT_T_ + 1274
16 Qanda 0x0000000103afc6b7 _TTRXFo__dT__XFdCb__dT__ + 39
17 libdispatch.dylib 0x0000000109dd7e5d _dispatch_call_block_and_release + 12
18 libdispatch.dylib 0x0000000109df849b _dispatch_client_callout + 8
19 libdispatch.dylib 0x0000000109de02af _dispatch_main_queue_callback_4CF + 1738
20 CoreFoundation 0x00000001090bad09 __CFRUNLOOP_IS_SERVICING_THE_MAIN_DISPATCH_QUEUE__ + 9
21 CoreFoundation 0x000000010907c2c9 __CFRunLoopRun + 2073
22 CoreFoundation 0x000000010907b828 CFRunLoopRunSpecific + 488
23 GraphicsServices 0x000000010c171ad2 GSEventRunModal + 161
24 UIKit 0x0000000106b34610 UIApplicationMain + 171
25 Qanda 0x0000000103bb537d main + 109
26 libdyld.dylib 0x0000000109e2c92d start + 1
)
libc++abi.dylib: terminating with uncaught exception of type NSException
以下是我的布局代码：
var numberOfColumns: Int = 1
let cellPadding: CGFloat = 10
let buttonContainerHeight: CGFloat = 50
let DEFAULT_HEIGHT: CGFloat = 80
private var contentWidth: CGFloat = UIScreen.mainScreen().bounds.width
private var totalContentHeight: CGFloat = 0.0
// Delegate
var delegate: HomeFeedCollectionViewLayoutDelegate?
var cache = [UICollectionViewLayoutAttributes]()
override func prepareLayout() {
// If cache is empty, calculate the layout
if cache.isEmpty {
// Set the size
let columnWidth = contentWidth / CGFloat(numberOfColumns)
var contentHeight: CGFloat = 0.0
var column = 0
let xOffset: CGFloat = 0
var yOffset: CGFloat = 0
var yOffsetArray = [CGFloat]()
// First check if sections actually exist
if collectionView!.numberOfSections() > 0 {
// Loop through items in section
for item in 0 ..< collectionView!.numberOfItemsInSection(0) {
let indexPath = NSIndexPath(forItem: item, inSection: 0)
let width = columnWidth - cellPadding * 2
let questionHeight = delegate?.collectionView(collectionView!, heightForQuestionAtIndexPath: indexPath, withWidth:width)
// Calculate frame
var height: CGFloat!
if questionHeight > 0 {
height = DEFAULT_HEIGHT + buttonContainerHeight + questionHeight! + 10
}
else {
height = contentWidth + buttonContainerHeight
}
if yOffsetArray.isEmpty {
log.debug("yOffsetArray is EMPTY")
}
else {
yOffset = yOffsetArray[item - 1] - cellPadding
}
yOffsetArray.append(height + yOffset)
let frame = CGRect(x: xOffset, y: yOffset, width: columnWidth, height: height)
let insetFrame = CGRectInset(frame, cellPadding, cellPadding)
// Create instance of UICollectionViewLayoutAttribute & set insetFrame
let attributes = UICollectionViewLayoutAttributes(forCellWithIndexPath: indexPath)
attributes.frame = insetFrame
cache.append(attributes)
// Make content height
contentHeight = contentHeight + (height - cellPadding)
column = column >= (numberOfColumns - 1) ? 0 : ++column
}
self.totalContentHeight = contentHeight
}
}
}
override func collectionViewContentSize() -> CGSize {
return CGSize(width: UIScreen.mainScreen().bounds.width, height: self.totalContentHeight + cellPadding)
}
override func layoutAttributesForElementsInRect(rect: CGRect) -> [UICollectionViewLayoutAttributes]? {
var layoutAttributes = [UICollectionViewLayoutAttributes]()
for attributes in cache {
if CGRectIntersectsRect(attributes.frame, rect) {
layoutAttributes.append(attributes)
}
}
return layoutAttributes
}
编辑：缩小错误的根目录，如果首先重新加载CV，则返回的UICollectionViewLayoutAttributes似乎只会更新为正确的新值。但是，如果我这样做，批量更新会抛出一个错误，说AFTER的总行数应该等于之前加上插入的数字......这是有道理的。
编辑2 ：现在我不知所措。批量更新是否尝试从默认布局检索布局而不是我的自定义布局？
layoutAttributesForElementsInRect = [<UICollectionViewLayoutAttributes: 0x7ffc1d8baf70> index path: (<NSIndexPath: 0xc000000000000016> {length = 2, path = 0 - 0}); frame = (10 10; 355 405); , <UICollectionViewLayoutAttributes: 0x7ffc1d8a5930> index path: (<NSIndexPath: 0xc000000000200016> {length = 2, path = 0 - 1}); frame = (10 425; 355 143.222); , <UICollectionViewLayoutAttributes: 0x7ffc1d837240> index path: (<NSIndexPath: 0xc000000000400016> {length = 2, path = 0 - 2}); frame = (10 578.222; 355 143.222); [...] <UICollectionViewLayoutAttributes: 0x7ffc1d8d02f0> index path: (<NSIndexPath: 0xc000000002600016> {length = 2, path = 0 - 19}); frame = (10 3229.44; 355 143.222); ]
*** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'no UICollectionViewLayoutAttributes instance for -layoutAttributesForItemAtIndexPath: <NSIndexPath: 0xc000000000200016> {length = 2, path = 0 - 1}'
这怎么可能？
答案 0 :(得分：9)
对于那些遇到同样问题的人，我发现你做的时候
self.collectionView?.performBatchUpdates({ () -> Void in
// add new items into collection
self.collectionView?.insertItemsAtIndexPaths(indexPaths)
}, completion: { (finished) -> Void in
// do insertion animations
});
未调用layoutAttributesForElementsInRect方法，而是调用layoutAttributesForItemAtIndexPath。
因此，您还必须覆盖自定义布局中的layoutAttributesForItemAtIndexPath，如下所示：
override func layoutAttributesForItemAtIndexPath(indexPath: NSIndexPath) -> UICollectionViewLayoutAttributes? {
// Logic that calculates the UICollectionViewLayoutAttributes of the item
// and returns the UICollectionViewLayoutAttributes
return self.singleItemLayout(indexPath)
}
编辑：此外，如果您遇到批处理insertItemsAtIndexPaths方法时遇到闪烁。