UICollectionView 自定义分页

- (void)prepareLayout {

    [super prepareLayout];

    self.collectionView.decelerationRate = UIScrollViewDecelerationRateFast;

    self.collectionView.pagingEnabled = false;

}

- (CGPoint)targetContentOffsetForProposedContentOffset:(CGPoint)proposedContentOffset withScrollingVelocity:(CGPoint)velocity {

    CGFloat pageWidth = self.itemSize.width + self.minimumLineSpacing;

    CGFloatapproximatePage =self.collectionView.contentOffset.x/ pageWidth;

    CGFloatcurrentPage = velocity.x==0?round(approximatePage) : (velocity.x<0.0?floor(approximatePage) :ceil(approximatePage));

    CGFloat margin = (self.collectionView.bounds.size.width - self.itemSize.width) * 0.5;

    CGFloatnewHorizontalOffset =self.sectionInset.left+ currentPage * pageWidth - margin;

    returnCGPointMake(newHorizontalOffset, proposedContentOffset.y);

}