UICollectionView isn't scrolling to indexPath

问题

I have a UICollectionView that I set the translatesAutoresizingMaskIntoConstraints to NO, and added some constraints. When I try scrolling it to an indexPath:

[self.datesCollectionView selectItemAtIndexPath:selectedCellIndexPath animated:YES scrollPosition:UICollectionViewScrollPositionCenteredHorizontally];

Then it completely ignores that, and doesn't scroll. But when I remove translatesAutoresizingMaskIntoConstraints, then it scrolls, but the constraints are ignored.

My question is, How can I get the collectionView to scroll to an indexPath when translatesAutoresizingMaskIntoConstraints is set to NO?

回答1:

After looking at your code, I found the problem. I'm not sure why this is the case, but the contentSize of the collection view was zero after applying the constraints. Adding a call to layoutIfNeeded to either setSelectedDate: or setDates: fixed the problem,

- (void)setDates:(NSArray *)dates {
    _dates = dates;
    [self.datesCollectionView layoutIfNeeded];
    [self.datesCollectionView reloadData];

    self.selectedDate = nil;
}

来源：https://stackoverflow.com/questions/30655351/uicollectionview-isnt-scrolling-to-indexpath