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