效果圖如下:

效果圖.png

具體代碼

• 繼承自UICollectionViewLayout

• LTCircleLayout.h文件

#import <UIKit/UIKit.h>

@interface LTCircleLayout : UICollectionViewLayout
//item尺寸
@property (nonatomic, assign) CGSize itemSize;
//內(nèi)邊距
@property (nonatomic) UIEdgeInsets sectionInset;
@end

• LTCircleLayout.m文件

#import "LTCircleLayout.h"

@interface LTCircleLayout ()
//屬性數(shù)組
@property (nonatomic, strong) NSMutableArray *attrsArray;
@end

@implementation LTCircleLayout

- (NSMutableArray *)attrsArray
{
    if (!_attrsArray) {
        self.attrsArray = [[NSMutableArray alloc] init];
    }
    return _attrsArray;
}

/**
 初始化設(shè)置
 */
- (void)prepareLayout
{
    [super prepareLayout];
    NSInteger rows = [self.collectionView numberOfItemsInSection:0];
    for (int i = 0; i < rows; i++) {
        NSIndexPath *indexPath = [NSIndexPath indexPathForRow:i inSection:0];
        UICollectionViewLayoutAttributes *attrs = [self layoutAttributesForItemAtIndexPath:indexPath];
        [self.attrsArray addObject:attrs];
    }
}

/**
 返回所有的cell的位置組成的數(shù)組, 在這里確定每一個(gè)cell的具體位置
 */
- (NSArray<UICollectionViewLayoutAttributes *> *)layoutAttributesForElementsInRect:(CGRect)rect
{
    return self.attrsArray;
}

/**
 這個(gè)方法需要返回indexPath位置對(duì)應(yīng)cell的布局屬性
 collectionView切換layout布局時(shí)必須實(shí)現(xiàn)的方法
 */
- (UICollectionViewLayoutAttributes *)layoutAttributesForItemAtIndexPath:(NSIndexPath *)indexPath
{
    NSInteger rows = [self.collectionView numberOfItemsInSection:indexPath.section];
    //圓心x
    CGFloat oX = self.collectionView.frame.size.width * 0.5;
    //圓心y
    CGFloat oY = self.collectionView.frame.size.height * 0.5;
    
    CGFloat width = self.collectionView.frame.size.width;
    CGFloat hegiht = self.collectionView.frame.size.height;
    //寬度直徑
    CGFloat widthDismeter = width - self.sectionInset.left - self.sectionInset.right;
    //高度直徑
    CGFloat hegihtDismeter = hegiht - self.sectionInset.top - self.sectionInset.bottom;
    //圓的半徑
    CGFloat raduis = (widthDismeter > hegihtDismeter ? hegihtDismeter : widthDismeter) * 0.5 - (self.itemSize.width > self.itemSize.height ? self.itemSize.height : self.itemSize.width) * 0.5;
    //計(jì)算cell的布局屬性
    UICollectionViewLayoutAttributes *attrs = [UICollectionViewLayoutAttributes layoutAttributesForCellWithIndexPath:indexPath];
    attrs.size = self.itemSize;
    CGFloat angle = 2 * M_PI / rows * indexPath.item;
    CGFloat centerX = oX + raduis * sin(angle);
    CGFloat centerY = oY + raduis * cos(angle);
    attrs.center = CGPointMake(centerX, centerY);
    
    return attrs;
}