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//[collectionView reloadData]后执行
- (void)shrinkToTopAnimationWithTableView:(UICollectionView *)collectionView {
[collectionView layoutSubviews];
//UICollectionView需先执行layoutSubviews 才可获取visibleCells
NSArray *cells = [collectionView visibleCells];
for (int i = 0; i < cells.count; i++) {
UICollectionViewCell *cell = [cells objectAtIndex:i];
cell.transform = CGAffineTransformMakeTranslation(0, 30);
cell.alpha = 0.5;
[UIView animateWithDuration:0.4 animations:^{
cell.transform = CGAffineTransformIdentity;
cell.alpha = 1;
}];
}
}
