UICollectionView（二）

3D效果

-(NSArray *)layoutAttributesForElementsInRect:(CGRect)rect
{
    NSArray *array = [super layoutAttributesForElementsInRect:rect];
    CGRect visibleRect;
    visibleRect.origin = self.collectionView.contentOffset;
    visibleRect.size = self.collectionView.bounds.size;

    for (UICollectionViewLayoutAttributes* attributes in array) {
        CGFloat distance = CGRectGetMidX(visibleRect) - attributes.center.x;
        NSLog(@"%f",distance);
        CGFloat normalizedDistance = distance / ActiveDistance;
        CGFloat zoom = 1 + ScaleFactor*(1 - ABS(normalizedDistance));
        //3D效果
        attributes.transform3D = CATransform3DMakeScale(1.0, zoom, 1.0);
        attributes.zIndex = 1;
    }
    return array;
}

分页

pagingEnabled = true //可根据页面宽度进行分页

特殊情况下需要根据代理方法去计算分页的距离

- (CGPoint)targetContentOffsetForProposedContentOffset:(CGPoint)offset
                                 withScrollingVelocity:(CGPoint)velocity

- (CGPoint)targetContentOffsetForProposedContentOffset:(CGPoint)offset
                                 withScrollingVelocity:(CGPoint)velocity {
    
    CGRect cvBounds = self.collectionView.bounds;
    CGFloat halfWidth = cvBounds.size.width * 0.5f;
    CGFloat proposedContentOffsetCenterX = offset.x + halfWidth;
    
    NSArray* attributesArray = [self layoutAttributesForElementsInRect:cvBounds];
    
    UICollectionViewLayoutAttributes* candidateAttributes;
    for (UICollectionViewLayoutAttributes* attributes in attributesArray) {
        
        // == Skip comparison with non-cell items (headers and footers) == //
        if (attributes.representedElementCategory !=
            UICollectionElementCategoryCell) {
            continue;
        }
        
        // == First time in the loop == //
        if(!candidateAttributes) {
            candidateAttributes = attributes;
            continue;
        }
        
        if (fabs(attributes.center.x - proposedContentOffsetCenterX) <
            fabs(candidateAttributes.center.x - proposedContentOffsetCenterX)) {
            candidateAttributes = attributes;
        }
    }
    
    return CGPointMake(candidateAttributes.center.x - halfWidth, offset.y);
    
}

引用 labmain.com/2017/02/12/… developer.apple.com/library/arc…