使用 UICollectionViewCompositionalLayout 并将标题视图固定到布局时发生崩溃

Question

我注意到在使用 NSCollectionLayoutBoundarySupplementaryItem 通过 UICollectionViewCompositionalLayoutConfiguration 将粘性标头添加到集合视图时，UICollectionViewCompositionalLayout 发生了崩溃。

这些网格视图标题项都通过 pinToVisibleBounds 属性固定到可见边界，以使它们在滚动行时具有粘性。

这是崩溃，

2022-04-09 00:28:56.335279-0700 *****[88274:5668805] *** Assertion failure in CGRect _UIPinnedFrameForFrameWithContainerFrameVisibleFrame(CGRect, CGRect, CGRect, NSRectAlignment)(), _UICollectionLayoutHelpers.m:688
2022-04-09 00:28:56.341980-0700 ******[88274:5668805] *** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'Frame {{377, 0}, {0, 627}} does not intersect {{377, 0}, {0, 627}}'
*** First throw call stack:
(
    0  CoreFoundation           0x000000010aa45d44 __exceptionPreprocess + 242
    1  libobjc.A.dylib           0x0000000107671a65 objc_exception_throw + 48
    2  Foundation             0x00000001089357d9 -[NSMutableDictionary(NSMutableDictionary) classForCoder] + 0
    3  UIKitCore              0x00000001187a09cb _UIPinnedNonOverlappingFramesForContentFrameVisibleFrame + 3154
    4  UIKitCore              0x00000001187b7ff4 -[_UICollectionLayoutAuxillaryItemSolver _solveForPinning:visibleRect:] + 5748
    5  UIKitCore              0x00000001187824ed -[_UICollectionCompositionalLayoutSolver updatePinnedSectionSupplementaryItemsForVisibleBounds:] + 723
    6  UIKitCore              0x000000011877e542 -[UICollectionViewCompositionalLayout _updatePinnedSectionSupplementaryItemsForCurrentVisibleBounds] + 381
    7  UIKitCore              0x000000011877f148 -[UICollectionViewCompositionalLayout _solveForPinnedSupplementaryItemsIfNeededWithContext:] + 121
    8  UIKitCore              0x000000011877a203 -[UICollectionViewCompositionalLayout invalidateLayoutWithContext:] + 802
    9  UIKitCore              0x000000011888770d -[UICollectionViewLayout _invalidateLayoutUsingContext:] + 56
    10 UIKitCore              0x00000001188202e5 -[UICollectionView setBounds:] + 757
    11 UIKitCore              0x0000000119713ab2 -[UIScrollView setContentOffset:] + 1047
    12 UIKitCore              0x0000000118839f2e -[UICollectionView setContentOffset:] + 42
    13 UIKitCore              0x0000000119728b6e -[UIScrollView _smoothScrollSyncWithUpdateTime:] + 3152
    14 UIKitCore              0x0000000119727b55 -[UIScrollView _smoothScrollWithUpdateTime:] + 313
    15 UIKitCore              0x0000000119728f06 -[UIScrollView _smoothScrollDisplayLink:] + 613
    16 QuartzCore             0x0000000113937474 _ZN2CA7Display11DisplayLink14dispatch_itemsEyyy + 932
    17 QuartzCore             0x0000000113a369c6 _ZL22display_timer_callbackP12__CFMachPortPvlS1_ + 395
    18 CoreFoundation           0x000000010a97eb42 __CFMachPortPerform + 157
    19 CoreFoundation           0x000000010a9b3125 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE1_PERFORM_FUNCTION__ + 41
    20 CoreFoundation           0x000000010a9b24cc __CFRunLoopDoSource1 + 617
    21 CoreFoundation           0x000000010a9ac901 __CFRunLoopRun + 2420
    22 CoreFoundation           0x000000010a9aba90 CFRunLoopRunSpecific + 562
    23 GraphicsServices          0x0000000110617c8e GSEventRunModal + 139
    24 UIKitCore              0x00000001191e490e -[UIApplication _run] + 928
    25 UIKitCore              0x00000001191e9569 UIApplicationMain + 101
    26 SEAnalyticsSDKSample        0x0000000106ec8b05 main + 229
    27 dyld                0x0000000107140f21 start_sim + 10
    28 ???                 0x000000011063d51e 0x0 + 4569945374
)
libc++abi: terminating with uncaught exception of type NSException

*** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'Frame {{377, 0}, {0, 627}} does not intersect {{377, 0}, {0, 627}}'
terminating with uncaught exception of type NSException

这是粗略的实现：

  func layout() -> UICollectionViewLayout {
    UICollectionViewCompositionalLayout(sectionProvider: { [self] section, _ in
      // Building section here 
    }, configuration: configuration)
  }
     
  var configuration: UICollectionViewCompositionalLayoutConfiguration {
    let configuration = UICollectionViewCompositionalLayoutConfiguration()

    var boundaryItems: [NSCollectionLayoutBoundarySupplementaryItem] = []

    var offset = 0
    for column in 0..<datasource.numberOfColumns {
      let columnHeaderSize = NSCollectionLayoutSize(widthDimension: .absolute(100), heightDimension: .absolute(44))

      let headerView = NSCollectionLayoutBoundarySupplementaryItem(
        layoutSize: columnHeaderSize,
        elementKind: "columnHeader",
        alignment: .topLeading,
        absoluteOffset: CGPoint(x: offset, y: 0)
      )

      headerView.pinToVisibleBounds = true
      headerView.zIndex = 2
       
      offset += 100.0
      boundaryItems.append(headerView)
    } 

    configuration.boundarySupplementaryItems = boundaryItems
    return configuration
  }

我试图了解导致此崩溃的原因以及如何防止发生此崩溃。

Answer 1

当集合视图中没有项目并且您将全局标题滚动出视口时，似乎会发生此崩溃。
就我而言，在没有项目时将 alwaysBounceVertical 设置为 false，并在将快照中的数据应用到 diffable 数据源之前将集合视图有要显示的项目时设置为 true，有助于解决此问题：

collectionView.alwaysBounceVertical = !collectionViewItems.isEmpty