我试图滚动到UITableView的底部后,它完成执行[自我。tableView reloadData]。
我原本有
[self.tableView reloadData]
NSIndexPath* indexPath = [NSIndexPath indexPathForRow: ([self.tableView numberOfRowsInSection:([self.tableView numberOfSections]-1)]-1) inSection: ([self.tableView numberOfSections]-1)];
[self.tableView scrollToRowAtIndexPath:indexPath atScrollPosition:UITableViewScrollPositionBottom animated:YES];
但后来我读到reloadData是异步的,所以自self以来滚动就没有发生。表视图,自我。tableView numberOfSections和[self.]tableView numberOfRowsinSection都是0。
很奇怪,我用的是:
[self.tableView reloadData];
NSLog(@"Number of Sections %d", [self.tableView numberOfSections]);
NSLog(@"Number of Rows %d", [self.tableView numberOfRowsInSection:([self.tableView numberOfSections]-1)]-1);
在控制台中,它返回Sections = 1, Row = -1;
当我在cellForRowAtIndexPath做完全相同的nslog时,我得到Sections = 1和Row = 8;(8是正确的)
和一个UICollectionView版本,基于kolaworld的答案。
它需要测试。到目前为止,它在iOS 9.2和Xcode 9.2 beta 2上工作,将collectionView滚动到一个索引,作为一个闭包。
extension UICollectionView
{
/// Calls reloadsData() on self, and ensures that the given closure is
/// called after reloadData() has been completed.
///
/// Discussion: reloadData() appears to be asynchronous. i.e. the
/// reloading actually happens during the next layout pass. So, doing
/// things like scrolling the collectionView immediately after a
/// call to reloadData() can cause trouble.
///
/// This method uses CATransaction to schedule the closure.
func reloadDataThenPerform(_ closure: @escaping (() -> Void))
{
CATransaction.begin()
CATransaction.setCompletionBlock(closure)
self.reloadData()
CATransaction.commit()
}
}
用法:
myCollectionView.reloadDataThenPerform {
myCollectionView.scrollToItem(at: indexPath,
at: .centeredVertically,
animated: true)
}