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我正在尝试在 UICollectionView 上实现捏合展开，但遇到了一些麻烦。与我能找到的所有示例代码不同，我没有将其作为交互式 UINavigationController 转换的一部分 - 我只需要就地展开一个项目。

这是我的捏手势识别器：

- (void)pinchGestureDidPinch:(UIPinchGestureRecognizer *)recognizer
{
    CGFloat targetScale = 3.0;
    CGFloat scale = recognizer.scale;
    if (recognizer.state == UIGestureRecognizerStateBegan) {
        CGPoint point = [recognizer locationInView:self.collectionView];
        NSIndexPath *rowUnder = [self.collectionView indexPathForItemAtPoint:point];
        self.pinchingRow = [NSIndexPath indexPathForItem:0 inSection:rowUnder.section];
        self.currentState = HACStreamViewControllerTransitioning;
        self.expandedLayout.expandedSection = self.pinchingRow.section;
        self.transitionLayout = [self.collectionView startInteractiveTransitionToCollectionViewLayout:self.expandedLayout completion:nil];
    } else if (recognizer.state == UIGestureRecognizerStateEnded || recognizer.state == UIGestureRecognizerStateCancelled) {
        if (scale >= targetScale) {
            [self.collectionView finishInteractiveTransition];
            self.currentState = HACStreamViewControllerExpanded;
        } else {
            [self.collectionView cancelInteractiveTransition];
            self.currentState = HACStreamViewControllerCollapsed;
        }
    } else {
        // change
        CGFloat progress = MIN(targetScale / scale, 1.0);
        progress = MAX(0.0, progress);
        self.transitionLayout.transitionProgress = progress;
        [self.transitionLayout invalidateLayout];
    }
}

调用 startInteractiveTransitionToCollectionViewLayout: 会导致异常：

0   ???                                 0x0fcf577f 0x0 + 265246591,
1   UIKit                               0x01e1f582 -[UICollectionViewTransitionLayout setTransitionProgress:] + 643,
2   UIKit                               0x01d13053 -[UICollectionView _setCollectionViewLayout:animated:isInteractive:completion:] + 658,
3   UIKit                               0x01d12be8 -[UICollectionView setCollectionViewLayout:] + 225,
4   UIKit                               0x01d15e0a -[UICollectionView startInteractiveTransitionToCollectionViewLayout:completion:] + 821,
5   HAW Couples                         0x0001beae -[HACStreamViewController pinchGestureDidPinch:] + 782,
6   UIKit                               0x01a74f8c _UIGestureRecognizerSendActions + 230,
7   UIKit                               0x01a73c00 -[UIGestureRecognizer _updateGestureWithEvent:buttonEvent:] + 383,
8   UIKit                               0x01a7566d -[UIGestureRecognizer _delayedUpdateGesture] + 60,
9   UIKit                               0x01a78bcd ___UIGestureRecognizerUpdate_block_invoke + 57,
10  UIKit                               0x01a78b4e _UIGestureRecognizerRemoveObjectsFromArrayAndApplyBlocks + 317,
11  UIKit                               0x01a6f248 _UIGestureRecognizerUpdate + 199,
12  UIKit                               0x0173bd4a -[UIWindow _sendGesturesForEvent:] + 1291,
13  UIKit                               0x0173cc6a -[UIWindow sendEvent:] + 1030,
14  UIKit                               0x01710a36 -[UIApplication sendEvent:] + 242,
15  UIKit                               0x016fad9f _UIApplicationHandleEventQueue + 11421,
16  CoreFoundation                      0x033988af __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ + 15,
17  CoreFoundation                      0x0339823b __CFRunLoopDoSources0 + 235,
18  CoreFoundation                      0x033b530e __CFRunLoopRun + 910,
19  CoreFoundation                      0x033b4b33 CFRunLoopRunSpecific + 467,
20  CoreFoundation                      0x033b494b CFRunLoopRunInMode + 123,
21  GraphicsServices                    0x042619d7 GSEventRunModal + 192,
22  GraphicsServices                    0x042617fe GSEventRun + 104,
23  UIKit                               0x016fd94b UIApplicationMain + 1225,
24  HAW Couples                         0x0000eefd main + 141,
25  libdyld.dylib                       0x03bd5725 start + 0

关于异常的消息：

*** setObjectForKey: object cannot be nil (key: actualAttribute)

我已经验证我的“目的地” UICollectionViewLayout 是好的。以下替代方案（由点击触发）工作正常，并按预期动画：

[self.collectionView setCollectionViewLayout:self.expandedLayout animated:YES completion:^(BOOL finished) {
}];
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1 回答 1

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我有完全相同的问题，在我的情况下，当布局之一是自定义布局而另一个是 UICollectionViewFlowLayout 时，就会发生这种崩溃。我仍在研究这个问题，但我想知道你是否有相同的设置。

编辑 1) 在我的自定义布局中，我有一个装饰视图，我在 [UICollectionViewLayout layoutAttributesForElementsInRect:] 操作中为装饰视图返回了 UICollectionViewLayoutAttributes。我在删除装饰视图的布局属性后进行了测试，现在它可以完美运行。一个布局中的装饰视图在另一个布局中不存在似乎是一个问题，当我找出更多信息时，我会更新我的答案。

于 2013-11-09T16:26:43.720 回答