动画 UICollectionView contentOffset 不显示不可见单元格

我正在开发一些类似股票行情的功能，并且正在使用UICollectionView。它最初是一个滚动视图，但我们认为集合视图将使添加/删除单元格变得更容易。

我使用以下内容对 collectionView 进行动画处理：

- (void)beginAnimation {
    [UIView animateWithDuration:((self.collectionView.collectionViewLayout.collectionViewContentSize.width - self.collectionView.contentOffset.x) / 75) delay:0 options:(UIViewAnimationOptionCurveLinear | UIViewAnimationOptionRepeat | UIViewAnimationOptionBeginFromCurrentState) animations:^{
        self.collectionView.contentOffset = CGPointMake(self.collectionView.collectionViewLayout.collectionViewContentSize.width, 0);
    } completion:nil];
}

这对于滚动视图效果很好，并且动画正在集合视图中发生。但是，实际上仅渲染动画结束时可见的单元格。调整 contentOffset 不会导致cellForItemAtIndexPath被称为。当 contentOffset 改变时，如何让单元格渲染？

编辑： 更多参考（不确定是否有很大帮助）：

- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath {
    TickerElementCell *cell = (TickerElementCell *)[collectionView dequeueReusableCellWithReuseIdentifier:@"TickerElementCell" forIndexPath:indexPath];
    cell.ticker = [self.fetchedResultsController objectAtIndexPath:indexPath];
    return cell;
}

- (void)controllerDidChangeContent:(NSFetchedResultsController *)controller {

    // ...

    [self loadTicker];
}

- (void)loadTicker {

    // ...

    if (self.animating) {
        [self updateAnimation];
    }
    else {
        [self beginAnimation];
    }
}

- (void)beginAnimation {

    if (self.animating) {
        [self endAnimation];
    }

    if ([self.tickerElements count] && !self.animating && !self.paused) {
        self.animating = YES;
        self.collectionView.contentOffset = CGPointMake(1, 0);
        [UIView animateWithDuration:((self.collectionView.collectionViewLayout.collectionViewContentSize.width - self.collectionView.contentOffset.x) / 75) delay:0 options:(UIViewAnimationOptionCurveLinear | UIViewAnimationOptionAllowUserInteraction | UIViewAnimationOptionRepeat | UIViewAnimationOptionBeginFromCurrentState) animations:^{
            self.collectionView.contentOffset = CGPointMake(self.collectionView.collectionViewLayout.collectionViewContentSize.width, 0);
        } completion:nil];
    }
}

你应该简单地添加[self.view layoutIfNeeded];在动画块内，如下所示：

[UIView animateWithDuration:((self.collectionView.collectionViewLayout.collectionViewContentSize.width - self.collectionView.contentOffset.x) / 75) delay:0 options:(UIViewAnimationOptionCurveLinear | UIViewAnimationOptionAllowUserInteraction | UIViewAnimationOptionRepeat | UIViewAnimationOptionBeginFromCurrentState) animations:^{
            self.collectionView.contentOffset = CGPointMake(self.collectionView.collectionViewLayout.collectionViewContentSize.width, 0);
            [self.view layoutIfNeeded];
        } completion:nil];