UICollectionView不重用单元格

Question

UICollectionView不重用单元格

in.*_*see 19 cocoa-touch reusability uicollectionview uicollectionviewcell ios7

我在重用单元格和UICollectionViewiOS 7上遇到了问题.我的代码在iOS 6上工作正常,但在iOS 7中,它在调用后不重用单元格dequeueReusableCellWithReuseIdentifier(不要调用prepareForReuse).

即使这个代码https://developer.apple.com/library/ios/samplecode/CollectionView-Simple/Introduction/Intro.html#//apple_ref/doc/uid/DTS40012860也不会重复使用iOS7上的单元格(但在iOS6上运行良好) ),每dequeueReusableCellWithReuseIdentifier创建一个新单元格并释放旧单元格.是否有一些新的东西阻止细胞重复使用？

我的细胞足够大,不再重复使用它们效率很低.我注意到iOS 7上的延迟,但iOS 6上没有,因为它们没有在iOS 7中重复使用.

Answer 1

Ale*_*rrù 17

我今天在iPad 3上遇到了同样的问题(只有三分之一的iPad 3我测试过),我发现它与全局辅助功能设置有关.解决方案是仔细检查辅助功能面板中的每个选项是否已禁用.我认为某些选项(例如更大的字体)可以保持启用状态,但我没有详细检查哪一个.

说明

查看堆栈跟踪,您可以看到:

#0  0x003121ce in -[MyCollectionViewCell initWithFrame:]
#1  0x32f945ec in -[UICollectionView _dequeueReusableViewOfKind:withIdentifier:forIndexPath:]
#2  0x04466656 in -[UICollectionViewAccessibility(SafeCategory) _dequeueReusableViewOfKind:withIdentifier:forIndexPath:]
#3  0x32f9414a in -[UICollectionView dequeueReusableCellWithReuseIdentifier:forIndexPath:]
#4  0x001767cc in -[MyCollectionView collectionView:cellForItemAtIndexPath:]

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正如您所看到的那样,有一个-[UICollectionViewAccessibility(SafeCategory) _dequeueReusableViewOfKind:withIdentifier:forIndexPath:]关于可访问性的引用.所以我进入了设置应用程序中的辅助功能设置,我发现我的辅助功能快捷方式的设置是"切换控制"而不是什么.所以我禁用它,我再次运行应用程序,我的堆栈跟踪现在很好:

#0  0x00313658 in -[MyCollectionViewCell prepareForReuse]
#1  0x32f942e6 in -[UICollectionView _dequeueReusableViewOfKind:withIdentifier:forIndexPath:]
#2  0x32f9414a in -[UICollectionView dequeueReusableCellWithReuseIdentifier:forIndexPath:]
#3  0x001767cc in -[MyCollectionView collectionView:cellForItemAtIndexPath:]

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Answer 2

lia*_*ols 5

更新 2：
事实证明这个答案是不正确的。请参阅下面的答案或单击此链接/sf/answers/1410345961/。

更新

所以我重新审视了这个答案，因为我发现了更多关于这个错误的信息..

我拿起了所有可用的设备，并对每台设备进行了相同的测试，结果如下：

DEVICE          OS Version      CELL REUSE
=============   =============   =============
iPad 4          7.0.0           YES
iPad 4          7.0.3           YES
iPad 3          7.0.3           NO
iPad 2          7.0.3           NO
iPad Mini       7.0.0           YES
iPad Mini       7.0.3           YES
iPhone 5s       7.0.3           YES
iPhone 4        7.0.2           YES
iPhone 4        7.0.3           YES

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如您所见，由于某种原因，单元重用似乎不适用于较旧的 iPad（无法渲染模糊的 iPad）。

我最初认为，由于某种性能问题，Apple 可能只是阻止了旧 iPad 的重复使用，但如果这是有道理的，iPhone 4 也会显示相同的结果。

为了在我的应用程序中解决这个问题，我在 collectionViewController 中有一个 NSMutableDictionary 并且我将我的单元格存储在那里，键是 indexPath .. 在我的情况下，这是可以的，因为我只有大约 9 个单元格并且它们的 indexPaths 永远不会改变但如果你需要更灵活的东西，那么检查 PSTCollectionView ( https://github.com/steipete/PSTCollectionView )也许是个好主意

刚刚在物理设备上对此进行了测试。它似乎在 iOS 7 和 6 上都可以正常工作，但在 iOS 7 模拟器上却没有！！！

只需在 collectionView 示例中放入一些日志：

@implementation Cell

- (id)initWithCoder:(NSCoder *)aDecoder
{
    NSLog(@"%s",__func__);
    self = [super initWithCoder:aDecoder];
    if (self)
    {
        CustomCellBackground *backgroundView = [[CustomCellBackground alloc] initWithFrame:CGRectZero];
        self.selectedBackgroundView = backgroundView;
    }
    return self;
}

-(void)prepareForReuse
{
    NSLog(@"%s",__func__);
}

-(void)dealloc
{
    NSLog(@"%s",__func__);
}

@end

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然后在所有三个设备上滚动到底部，这是输出：

iOS 7 模拟器

2013-10-09 17:42:45.798 CollViewSmpl[9547:a0b] -[Cell initWithCoder:]
2013-10-09 17:42:45.807 CollViewSmpl[9547:a0b] -[Cell initWithCoder:]
2013-10-09 17:42:45.811 CollViewSmpl[9547:a0b] -[Cell initWithCoder:]
2013-10-09 17:42:45.841 CollViewSmpl[9547:a0b] -[Cell initWithCoder:]
2013-10-09 17:42:45.844 CollViewSmpl[9547:a0b] -[Cell initWithCoder:]
2013-10-09 17:42:45.848 CollViewSmpl[9547:a0b] -[Cell initWithCoder:]
2013-10-09 17:42:45.852 CollViewSmpl[9547:a0b] -[Cell initWithCoder:]
2013-10-09 17:42:45.857 CollViewSmpl[9547:a0b] -[Cell initWithCoder:]
2013-10-09 17:42:47.080 CollViewSmpl[9547:a0b] -[Cell initWithCoder:]
2013-10-09 17:42:47.083 CollViewSmpl[9547:a0b] -[Cell initWithCoder:]
2013-10-09 17:42:47.181 CollViewSmpl[9547:a0b] -[Cell initWithCoder:]
2013-10-09 17:42:47.183 CollViewSmpl[9547:a0b] -[Cell initWithCoder:]
2013-10-09 17:42:47.208 CollViewSmpl[9547:a0b] -[Cell dealloc]
2013-10-09 17:42:47.208 CollViewSmpl[9547:a0b] -[Cell dealloc]
2013-10-09 17:42:47.214 CollViewSmpl[9547:a0b] -[Cell initWithCoder:]
2013-10-09 17:42:47.218 CollViewSmpl[9547:a0b] -[Cell initWithCoder:]
2013-10-09 17:42:47.245 CollViewSmpl[9547:a0b] -[Cell dealloc]
2013-10-09 17:42:47.246 CollViewSmpl[9547:a0b] -[Cell dealloc]
2013-10-09 17:42:47.264 CollViewSmpl[9547:a0b] -[Cell initWithCoder:]
2013-10-09 17:42:47.268 CollViewSmpl[9547:a0b] -[Cell initWithCoder:]
2013-10-09 17:42:47.289 CollViewSmpl[9547:a0b] -[Cell dealloc]
2013-10-09 17:42:47.290 CollViewSmpl[9547:a0b] -[Cell dealloc]
2013-10-09 17:42:47.317 CollViewSmpl[9547:a0b] -[Cell initWithCoder:]
2013-10-09 17:42:47.322 CollViewSmpl[9547:a0b] -[Cell initWithCoder:]
2013-10-09 17:42:47.343 CollViewSmpl[9547:a0b] -[Cell dealloc]
2013-10-09 17:42:47.344 CollViewSmpl[9547:a0b] -[Cell dealloc]
2013-10-09 17:42:47.364 CollViewSmpl[9547:a0b] -[Cell initWithCoder:]
2013-10-09 17:42:47.367 CollViewSmpl[9547:a0b] -[Cell initWithCoder:]
2013-10-09 17:42:47.401 CollViewSmpl[9547:a0b] -[Cell dealloc]
2013-10-09 17:42:47.402 CollViewSmpl[9547:a0b] -[Cell dealloc]
2013-10-09 17:42:47.430 CollViewSmpl[9547:a0b] -[Cell initWithCoder:]
2013-10-09 17:42:47.432 CollViewSmpl[9547:a0b] -[Cell initWithCoder:]
2013-10-09 17:42:47.472 CollViewSmpl[9547:a0b] -[Cell dealloc]
2013-10-09 17:42:47.472 CollViewSmpl[9547:a0b] -[Cell dealloc]
2013-10-09 17:42:47.498 CollViewSmpl[9547:a0b] -[Cell initWithCoder:]
2013-10-09 17:42:47.505 CollViewSmpl[9547:a0b] -[Cell initWithCoder:]
2013-10-09 17:42:47.561 CollViewSmpl[9547:a0b] -[Cell dealloc]
2013-10-09 17:42:47.562 CollViewSmpl[9547:a0b] -[Cell dealloc]
2013-10-09 17:42:47.585 CollViewSmpl[9547:a0b] -[Cell initWithCoder:]
2013-10-09 17:42:47.587 CollViewSmpl[9547:a0b] -[Cell initWithCoder:]
2013-10-09 17:42:47.624 CollViewSmpl[9547:a0b] -[Cell dealloc]
2013-10-09 17:42:47.624 CollViewSmpl[9547:a0b] -[Cell dealloc]
2013-10-09 17:42:47.669 CollViewSmpl[9547:a0b] -[Cell initWithCoder:]
2013-10-09 17:42:47.674 CollViewSmpl[9547:a0b] -[Cell initWithCoder:]
2013-10-09 17:42:47.797 CollViewSmpl[9547:a0b] -[Cell initWithCoder:]
2013-10-09 17:42:47.799 CollViewSmpl[9547:a0b] -[Cell initWithCoder:]
2013-10-09 17:42:47.809 CollViewSmpl[9547:a0b] -[Cell dealloc]
2013-10-09 17:42:47.809 CollViewSmpl[9547:a0b] -[Cell dealloc]
2013-10-09 17:42:47.810 CollViewSmpl[9547:a0b] -[Cell dealloc]
2013-10-09 17:42:47.810 CollViewSmpl[9547:a0b] -[Cell dealloc]
2013-10-09 17:42:47.964 CollViewSmpl[9547:a0b] -[Cell initWithCoder:]
2013-10-09 17:42:47.966 CollViewSmpl[9547:a0b] -[Cell initWithCoder:]
2013-10-09 17:42:47.987 CollViewSmpl[9547:a0b] -[Cell dealloc]
2013-10-09 17:42:47.987 CollViewSmpl[9547:a0b] -[Cell dealloc]

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iOS 6 设备 (iPhone 5)

2013-10-09 17:45:42.173 CollViewSmpl[187:907] -[Cell initWithCoder:]
2013-10-09 17:45:42.191 CollViewSmpl[187:907] -[Cell initWithCoder:]
2013-10-09 17:45:42.205 CollViewSmpl[187:907] -[Cell initWithCoder:]
2013-10-09 17:45:42.217 CollViewSmpl[187:907] -[Cell initWithCoder:]
2013-10-09 17:45:42.230 CollViewSmpl[187:907] -[Cell initWithCoder:]
2013-10-09 17:45:42.242 CollViewSmpl[187:907] -[Cell initWithCoder:]
2013-10-09 17:45:42.253 CollViewSmpl[187:907] -[Cell initWithCoder:]
2013-10-09 17:45:42.264 CollViewSmpl[187:907] -[Cell initWithCoder:]
2013-10-09 17:45:43.630 CollViewSmpl[187:907] -[Cell initWithCoder:]
2013-10-09 17:45:43.640 CollViewSmpl[187:907] -[Cell initWithCoder:]
2013-10-09 17:45:43.697 CollViewSmpl[187:907] -[Cell prepareForReuse]
2013-10-09 17:45:43.706 CollViewSmpl[187:907] -[Cell prepareForReuse]
2013-10-09 17:45:43.777 CollViewSmpl[187:907] -[Cell prepareForReuse]
2013-10-09 17:45:43.791 CollViewSmpl[187:907] -[Cell prepareForReuse]
2013-10-09 17:45:43.844 CollViewSmpl[187:907] -[Cell prepareForReuse]
2013-10-09 17:45:43.855 CollViewSmpl[187:907] -[Cell prepareForReuse]
2013-10-09 17:45:43.927 CollViewSmpl[187:907] -[Cell prepareForReuse]
2013-10-09 17:45:43.937 CollViewSmpl[187:907] -[Cell prepareForReuse]
2013-10-09 17:45:44.027 CollViewSmpl[187:907] -[Cell prepareForReuse]
2013-10-09 17:45:44.037 CollViewSmpl[187:907] -[Cell prepareForReuse]
2013-10-09 17:45:44.144 CollViewSmpl[187:907] -[Cell prepareForReuse]
2013-10-09 17:45:44.155 CollViewSmpl[187:907] -[Cell prepareForReuse]
2013-10-09 17:45:44.311 CollViewSmpl[187:907] -[Cell prepareForReuse]
2013-10-09 17:45:44.324 CollViewSmpl[187:907] -[Cell prepareForReuse]
2013-10-09 17:45:44.560 CollViewSmpl[187:907] -[Cell prepareForReuse]
2013-10-09 17:45:44.571 CollViewSmpl[187:907] -[Cell prepareForReuse]
2013-10-09 17:45:45.027 CollViewSmpl[187:907] -[Cell prepareForReuse]
2013-10-09 17:45:45.040 CollViewSmpl[187:907] -[Cell prepareForReuse]
2013-10-09 17:45:45.397 CollViewSmpl[187:907] -[Cell prepareForReuse]
2013-10-09 17:45:45.407 CollViewSmpl[187:907] -[Cell prepareForReuse]
2013-10-09 17:45:45.494 CollViewSmpl[187:907] -[Cell prepareForReuse]
2013-10-09 17:45:45.503 CollViewSmpl[187:907] -[Cell prepareForReuse]

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iOS 7 设备 (iPhone 5s)

2013-10-09 17:44:37.603 CollViewSmpl[871:60b] -[Cell initWithCoder:]
2013-10-09 17:44:38.015 CollViewSmpl[871:60b] -[Cell initWithCoder:]
2013-10-09 17:44:38.029 CollViewSmpl[871:60b] -[Cell initWithCoder:]
2013-10-09 17:44:38.037 CollViewSmpl[871:60b] -[Cell initWithCoder:]
2013-10-09 17:44:38.045 CollViewSmpl[871:60b] -[Cell initWithCoder:]
2013-10-09 17:44:38.053 CollViewSmpl[871:60b] -[Cell initWithCoder:]
2013-10-09 17:44:38.061 CollViewSmpl[871:60b] -[Cell initWithCoder:]
2013-10-09 17:44:38.071 CollViewSmpl[871:60b] -[Cell initWithCoder:]
2013-10-09 17:44:39.470 CollViewSmpl[871:60b] -[Cell initWithCoder:]
2013-10-09 17:44:39.483 CollViewSmpl[871:60b] -[Cell initWithCoder:]
2013-10-09 17:44:39.535 CollViewSmpl[871:60b] -[Cell prepareForReuse]
2013-10-09 17:44:39.540 CollViewSmpl[871:60b] -[Cell prepareForReuse]
2013-10-09 17:44:39.583 CollViewSmpl[871:60b] -[Cell prepareForReuse]
2013-10-09 17:44:39.587 CollViewSmpl[871:60b] -[Cell prepareForReuse]
2013-10-09 17:44:39.633 CollViewSmpl[871:60b] -[Cell prepareForReuse]
2013-10-09 17:44:39.637 CollViewSmpl[871:60b] -[Cell prepareForReuse]
2013-10-09 17:44:39.683 CollViewSmpl[871:60b] -[Cell prepareForReuse]
2013-10-09 17:44:39.688 CollViewSmpl[871:60b] -[Cell prepareForReuse]
2013-10-09 17:44:39.733 CollViewSmpl[871:60b] -[Cell prepareForReuse]
2013-10-09 17:44:39.737 CollViewSmpl[871:60b] -[Cell prepareForReuse]
2013-10-09 17:44:39.783 CollViewSmpl[871:60b] -[Cell initWithCoder:]
2013-10-09 17:44:39.791 CollViewSmpl[871:60b] -[Cell initWithCoder:]
2013-10-09 17:44:39.866 CollViewSmpl[871:60b] -[Cell prepareForReuse]
2013-10-09 17:44:39.870 CollViewSmpl[871:60b] -[Cell prepareForReuse]
2013-10-09 17:44:39.933 CollViewSmpl[871:60b] -[Cell prepareForReuse]
2013-10-09 17:44:39.938 CollViewSmpl[871:60b] -[Cell prepareForReuse]
2013-10-09 17:44:40.033 CollViewSmpl[871:60b] -[Cell prepareForReuse]
2013-10-09 17:44:40.036 CollViewSmpl[871:60b] -[Cell prepareForReuse]
2013-10-09 17:44:40.149 CollViewSmpl[871:60b] -[Cell prepareForReuse]
2013-10-09 17:44:40.152 CollViewSmpl[871:60b] -[Cell prepareForReuse]
2013-10-09 17:44:40.300 CollViewSmpl[871:60b] -[Cell prepareForReuse]
2013-10-09 17:44:40.304 CollViewSmpl[871:60b] -[Cell prepareForReuse]
2013-10-09 17:44:40.650 CollViewSmpl[871:60b] -[Cell prepareForReuse]
2013-10-09 17:44:40.652 CollViewSmpl[871:60b] -[Cell prepareForReuse]

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您可以看出在 iOS 6 和 7 中重用之间发生了一些变化，因为 1) 它在模拟器中不起作用 2) 如果您开始快速滚动，则单元格最初还没有准备好重用所以它必须创建一个新的来弥补 iOS 6 没有的地方（见我的日志）。

我花了半天时间试图修复一个只发生在模拟器上的错误。

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