Question

这曾经在iOS 6中运行但在iOS 7中失败

- (void)viewWillAppear:(BOOL)animated
{
    [super viewWillAppear:animated];

    NSIndexPath *indexPath = [NSIndexPath indexPathForItem:1 inSection:0];
    [self.collectionView selectItemAtIndexPath:indexPath animated:NO scrollPosition:UICollectionViewScrollPositionNone];
    NSArray *selectedPaths = self.collectionView.indexPathsForSelectedItems;
    NSAssert(selectedPaths.count == 1, @"viewWillAppear - Should be 1 but is %d", selectedPaths.count);
}

- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
    NSArray *selectedPaths = collectionView.indexPathsForSelectedItems;
    NSAssert(selectedPaths.count == 1, @"cellForItemAtIndexPath - Should be 1 but is %d", selectedPaths.count);
}

cellForItemAtIndexPath中的断言失败：

* 由于未捕获的异常'NSInternalInconsistencyException'而终止应用程序，原因：'cellForItemAtIndexPath - 应为1但是为0'

我使用selectItemAtIndexPath：indexPath API在viewWillAppear中选择一个项目，但是当调用cellForItemAtIndexPath时，collectionView忘记了已选择任何内容。知道为什么吗？

Answer 1

卫生署！

UICollectionViewController.clearsSelectionOnViewWillAppear

为什么UICollectionView.indexPathsForSelectedItems忘记了我在viewWillAppear中选择了一个项目？

1 个答案: