UICollectionView自定义布局( 封面布局)

UICollectionView自定义布局 封面布局

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布局文件：

MKCoverFlowLayout.h

import <UIKit/UIKit.h>

@interface MKCoverFlowLayout : UICollectionViewFlowLayout
@end

MKCoverFlowLayout.m

import "MKCoverFlowLayout.h"

@implementation MKCoverFlowLayout
#define ZOOM_FACTOR 0.35

-(void) prepareLayout {

//水平滚动
self.scrollDirection = UICollectionViewScrollDirectionHorizontal;
CGSize size = self.collectionView.frame.size;
self.itemSize = CGSizeMake(size.width/4.0f, size.height*0.7);
self.sectionInset = UIEdgeInsetsMake(size.height * 0.15, size.height * 0.1, size.height * 0.15, size.height * 0.1);
}

- (BOOL)shouldInvalidateLayoutForBoundsChange:(CGRect)oldBounds
{
return YES;
}

-(NSArray)layoutAttributesForElementsInRect:(CGRect)rect
{
NSArray array = [super layoutAttributesForElementsInRect:rect];
CGRect visibleRect;
visibleRect.origin = self.collectionView.contentOffset;
visibleRect.size = self.collectionView.bounds.size;
float collectionViewHalfFrame = self.collectionView.frame.size.width/2.0f;
for (UICollectionViewLayoutAttributes* attributes in array) {

if (CGRectIntersectsRect(attributes.frame, rect)) {

CGFloat distance = CGRectGetMidX(visibleRect) - attributes.center.x;
CGFloat normalizedDistance = distance / collectionViewHalfFrame;
if (ABS(distance) < collectionViewHalfFrame) {
CGFloat zoom = 1 + ZOOM_FACTOR*(1 - ABS(normalizedDistance));

//3D变化
//旋转的角度随着离中心的距离而按比例增加
//如果物件在中间，其旋转角度为0
//角度随着离中心的距离二而比例增加
CATransform3D rotationAndPerspectiveTransform = CATransform3DIdentity;
rotationAndPerspectiveTransform.m34 = 1.0 / -500;
rotationAndPerspectiveTransform = CATransform3DRotate(rotationAndPerspectiveTransform, (normalizedDistance) * M_PI_4, 0.0f, 1.0f, 0.0f);
CATransform3D zoomTransform = CATransform3DMakeScale(zoom, zoom, 1.0);
attributes.transform3D = CATransform3DConcat(zoomTransform, rotationAndPerspectiveTransform);

attributes.zIndex = ABS(normalizedDistance) * 10.0f;
CGFloat alpha = (1 - ABS(normalizedDistance)) + 0.1;
if(alpha > 1.0f) alpha = 1.0f;
attributes.alpha = alpha;
} else {

attributes.alpha = 0.0f;
}
}
}
return array;
}

@end