我有一个显示 UICollectionViewController 的 iPhone 应用程序。集合视图包含具有 UILabel 作为子视图的单元格。
考虑以下测试代码：
- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *CellIdentifier = @"Cell";
UICollectionViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:CellIdentifier forIndexPath:indexPath];
UILabel *label = (UILabel *)[cell viewWithTag:1];
label.text = [NSString stringWithFormat:@"%d", indexPath.row];
return cell;
}
- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection: (NSInteger)section
{
return 500;
}
当我运行应用程序并在集合视图中上下滚动时，XCode 5s 调试视图 (CMD-6) 中显示的内存使用量将稳步增加。这是预期的行为还是我在某处有泄漏？
Interface Builder 中的Collection reusable view identifier设置为Cell。
编辑： 我在 Instruments 中分析了测试应用程序，这是在滚动时似乎增长的调用的深层副本：
Bytes Used Count Symbol Name
1.01 MB 24.2% 24251 +[NSObject allocWithZone:]
229.95 KB 5.3% 2774 -[UINibDecoder decodeObjectForKey:]
173.25 KB 4.0% 2376 -[UIView initWithCoder:]
111.38 KB 2.6% 1980 -[UICollectionReusableView initWithCoder:]
111.38 KB 2.6% 1980 -[UICollectionViewCell initWithCoder:]
111.38 KB 2.6% 1980 -[UINibDecoder decodeObjectForKey:]
111.38 KB 2.6% 1980 -[UINib instantiateWithOwner:options:]
111.38 KB 2.6% 1980 -[UICollectionView _dequeueReusableViewOfKind:withIdentifier:forIndexPath:]
111.38 KB 2.6% 1980 -[UICollectionViewAccessibility(SafeCategory) _dequeueReusableViewOfKind:withIdentifier:forIndexPath:]
111.38 KB 2.6% 1980 -[UICollectionView dequeueReusableCellWithReuseIdentifier:forIndexPath:]
111.38 KB 2.6% 1980 -[CVTViewController collectionView:cellForItemAtIndexPath:]
111.38 KB 2.6% 1980 -[UICollectionView _createPreparedCellForItemAtIndexPath:withLayoutAttributes:applyAttributes:]
111.38 KB 2.6% 1980 -[UICollectionView _updateVisibleCellsNow:]
111.38 KB 2.6% 1980 -[UICollectionView layoutSubviews]
111.38 KB 2.6% 1980 -[UIView(CALayerDelegate) layoutSublayersOfLayer:]
111.38 KB 2.6% 1980 -[NSObject performSelector:withObject:]
111.38 KB 2.6% 1980 -[CALayer layoutSublayers]
61.88 KB 1.4% 396 -[UINibDecoder decodeObjectForKey:]
61.88 KB 1.4% 396 -[UIView initWithCoder:]
61.88 KB 1.4% 396 -[UICollectionReusableView initWithCoder:]
61.88 KB 1.4% 396 -[UICollectionViewCell initWithCoder:]
61.88 KB 1.4% 396 -[UINibDecoder decodeObjectForKey:]
61.88 KB 1.4% 396 -[UINib instantiateWithOwner:options:]
61.88 KB 1.4% 396 -[UICollectionView _dequeueReusableViewOfKind:withIdentifier:forIndexPath:]
61.88 KB 1.4% 396 -[UICollectionViewAccessibility(SafeCategory) _dequeueReusableViewOfKind:withIdentifier:forIndexPath:]
61.88 KB 1.4% 396 -[UICollectionView dequeueReusableCellWithReuseIdentifier:forIndexPath:]
61.88 KB 1.4% 396 -[CVTViewController collectionView:cellForItemAtIndexPath:]
61.88 KB 1.4% 396 -[UICollectionView _createPreparedCellForItemAtIndexPath:withLayoutAttributes:applyAttributes:]
61.88 KB 1.4% 396 -[UICollectionView _updateVisibleCellsNow:]
61.88 KB 1.4% 396 -[UICollectionView layoutSubviews]
61.88 KB 1.4% 396 -[UIView(CALayerDelegate) layoutSublayersOfLayer:]
61.88 KB 1.4% 396 -[NSObject performSelector:withObject:]
61.88 KB 1.4% 396 -[CALayer layoutSublayers]
55.69 KB 1.3% 396 -[UINib instantiateWithOwner:options:]
55.69 KB 1.3% 396 -[UICollectionView _dequeueReusableViewOfKind:withIdentifier:forIndexPath:]
55.69 KB 1.3% 396 -[UICollectionViewAccessibility(SafeCategory) _dequeueReusableViewOfKind:withIdentifier:forIndexPath:]
55.69 KB 1.3% 396 -[UICollectionView dequeueReusableCellWithReuseIdentifier:forIndexPath:]
55.69 KB 1.3% 396 -[CVTViewController collectionView:cellForItemAtIndexPath:]
55.69 KB 1.3% 396 -[UICollectionView _createPreparedCellForItemAtIndexPath:withLayoutAttributes:applyAttributes:]
55.69 KB 1.3% 396 -[UICollectionView _updateVisibleCellsNow:]
55.69 KB 1.3% 396 -[UICollectionView layoutSubviews]
55.69 KB 1.3% 396 -[UIView(CALayerDelegate) layoutSublayersOfLayer:]
55.69 KB 1.3% 396 -[NSObject performSelector:withObject:]
55.69 KB 1.3% 396 -[CALayer layoutSublayers]
（...缩写...）