objective-c - ios sliding problem about tableview or scrollView

Question

If the title is like this, the effect I want to achieve is during the process of sliding down. For example, the picture below is made with tableview. Now when you slide it here, it will not move. The effect I want to achieve is that the blue color does not reach half of the screen (approximately That position is OK), it will automatically return to the first row, which is only the red row...

欧阳克 · Answer

You are talking about card layout, you can use UICollectionView and custom UICollectionViewFlowLayout to achieve it, Demo address

// 修改cell滑动时大小
- (NSArray *)layoutAttributesForElementsInRect:(CGRect)rect
{
    
    NSArray *attrs = [[NSArray alloc] initWithArray:[super layoutAttributesForElementsInRect:self.collectionView.bounds] copyItems:YES];
    CGFloat scale;
    CGFloat offset;
    for (UICollectionViewLayoutAttributes *attr in attrs) {
        // 设置collection在滑动时, cell的大小
        if (self.scrollDirection == UICollectionViewScrollDirectionHorizontal) {
            offset = fabs(attr.center.x - self.collectionView.contentOffset.x - self.collectionView.bounds.size.width * 0.5);
            scale = 1 - offset / (self.collectionView.bounds.size.width * 0.5) * 0.25;
            attr.transform = CGAffineTransformMakeScale(scale, scale);
        } else {
            offset = fabs(attr.center.y - self.collectionView.contentOffset.y - self.collectionView.bounds.size.height * 0.5);
            scale = 1 - offset / (self.collectionView.bounds.size.height * 0.5) * 0.25;
            
        }
        attr.transform = CGAffineTransformMakeScale(scale, scale);
    }
    
    return attrs;
}

// 返回collection滑动手指松开后, collection最终的contentOffset
- (CGPoint)targetContentOffsetForProposedContentOffset:(CGPoint)proposedContentOffset withScrollingVelocity:(CGPoint)velocity
{
    if (self.scrollDirection == UICollectionViewScrollDirectionHorizontal) {
        // cell 宽度
        CGFloat itemW = self.itemSize.width;
        // cell边框距离(未设置collection的contentInset, 默认为0)
        CGFloat margin = self.collectionView.contentInset.left;
        // collection在手指松开后,collection滑动到停止时, collectioncontentOffset
        CGFloat index = roundf((proposedContentOffset.x + margin) / itemW);
        // 修改collection最终的contentOffset, 使collection滑动到cell中间
        proposedContentOffset.x = index * self.collectionView.bounds.size.width - (index + 1) * margin;
    } else {
        CGFloat itemH = self.itemSize.height;
        CGFloat margin = self.collectionView.contentInset.top;
        CGFloat index = roundf((proposedContentOffset.y + margin) / itemH);
        proposedContentOffset.y = index * self.collectionView.bounds.size.height - (index+1) * margin;
    }
    return proposedContentOffset;
}