UICollectionView Cell 居左 居中 居右

样式

左中右

自定义代码

// cell 排版 Typesetting 左 Left 中 Center 右 Right

#import <UIKit/UIKit.h>

NS_ASSUME_NONNULL_BEGIN

typedef NS_ENUM(NSInteger, AlignType) {
    AlignWithLeft,
    AlignWithCenter,
    AlignWithRight
};

@interface BaseTypesettingFlowLayout : UICollectionViewFlowLayout

- (instancetype)initWthType:(AlignType)cellType;
/// 全能初始化方法 其他方式初始化最终都会走到这里
- (instancetype)initWithType:(AlignType)cellType betweenOfCell:(CGFloat)betweenOfCell sectionInsetCell:(UIEdgeInsets)sectionInsetCell;

@property (nonatomic, assign) UIEdgeInsets sectionInsetCell;///<
@property (nonatomic, assign) CGFloat betweenOfCell; ///< 两个Cell之间的距离
@property (nonatomic, assign) AlignType cellType; /// cell对齐方式

@end

NS_ASSUME_NONNULL_END

// cell 排版 Typesetting 左 Left 中 Center 右 Right

#import "BaseTypesettingFlowLayout.h"

@interface BaseTypesettingFlowLayout()

@property (nonatomic, assign) CGFloat sumCellWidth; ///< 在居中对齐的时候需要知道这行所有cell的宽度总和

@end

@implementation BaseTypesettingFlowLayout

- (instancetype)init
{
    return [self initWithType:AlignWithCenter betweenOfCell:5.0 sectionInsetCell:UIEdgeInsetsMake(5, 5, 5, 5)];
}

- (void)setSectionInsetCell:(UIEdgeInsets)sectionInsetCell
{
    _sectionInsetCell = sectionInsetCell;
    self.sectionInset = sectionInsetCell;
}

- (void)setBetweenOfCell:(CGFloat)betweenOfCell
{
    _betweenOfCell = betweenOfCell;
    self.minimumInteritemSpacing = betweenOfCell;
}

- (instancetype)initWthType:(AlignType)cellType
{
    return [self initWithType:cellType betweenOfCell:5.0 sectionInsetCell:UIEdgeInsetsMake(5, 5, 5, 5)];
}

- (instancetype)initWithType:(AlignType)cellType betweenOfCell:(CGFloat)betweenOfCell sectionInsetCell:(UIEdgeInsets)sectionInsetCell
{
    self = [super init];
    if (self) {
        self.scrollDirection = UICollectionViewScrollDirectionVertical;
        self.minimumLineSpacing = 5;
        self.minimumInteritemSpacing = betweenOfCell;
        self.sectionInset = sectionInsetCell;//UIEdgeInsetsMake(5, 5, 5, 5);
        _betweenOfCell = betweenOfCell;
        _cellType = cellType;
    }
    return self;
}

- (NSArray *)layoutAttributesForElementsInRect:(CGRect)rect
{
    NSArray *layoutAttributes_t = [super layoutAttributesForElementsInRect:rect];
    NSArray *layoutAttributes = [[NSArray alloc] initWithArray:layoutAttributes_t copyItems:YES];
    //用来临时存放一行的Cell数组
    NSMutableArray *layoutAttributesTemp = [[NSMutableArray alloc]init];
    for (NSUInteger index = 0; index < layoutAttributes.count; index++)
    {
        UICollectionViewLayoutAttributes *currentAttr = layoutAttributes[index]; // 当前cell的位置信息
        UICollectionViewLayoutAttributes *previousAttr = index == 0 ? nil : layoutAttributes[index-1]; // 上一个cell 的位置信
        UICollectionViewLayoutAttributes *nextAttr = index + 1 == layoutAttributes.count ?
        nil : layoutAttributes[index+1];//下一个cell 位置信息
   
        //加入临时数组
        [layoutAttributesTemp addObject:currentAttr];
        self.sumCellWidth += currentAttr.frame.size.width;
        
        CGFloat previousY = previousAttr == nil ? 0 : CGRectGetMaxY(previousAttr.frame);
        CGFloat currentY = CGRectGetMaxY(currentAttr.frame);
        CGFloat nextY = nextAttr == nil ? 0 : CGRectGetMaxY(nextAttr.frame);
        //如果当前cell是单独一行
        if (currentY != previousY && currentY != nextY)
        {
            if ([currentAttr.representedElementKind isEqualToString:UICollectionElementKindSectionHeader])
            {
                [layoutAttributesTemp removeAllObjects];
                self.sumCellWidth = 0.0;
            }
            else if ([currentAttr.representedElementKind isEqualToString:UICollectionElementKindSectionFooter])
            {
                [layoutAttributesTemp removeAllObjects];
                self.sumCellWidth = 0.0;
            }
            else
            {
                [self setCellFrameWith:layoutAttributesTemp];
            }
        }
        // 如果下一个cell在本行，这开始调整Frame位置
        else if (currentY != nextY)
        {
            [self setCellFrameWith:layoutAttributesTemp];
        }
    }
    return layoutAttributes;
}

/// 调整属于同一行的cell的位置frame
- (void)setCellFrameWith:(NSMutableArray*)layoutAttributes
{
    CGFloat nowWidth = 0.0;
    switch (_cellType)
    {
        case AlignWithLeft:
            nowWidth = self.sectionInset.left;
            for (UICollectionViewLayoutAttributes *attributes in layoutAttributes)
            {
                CGRect nowFrame = attributes.frame;
                nowFrame.origin.x = nowWidth;
                attributes.frame = nowFrame;
                nowWidth += nowFrame.size.width + self.betweenOfCell;
            }
            self.sumCellWidth = 0.0;
            [layoutAttributes removeAllObjects];
            break;
        case AlignWithCenter:
            nowWidth = (self.collectionView.frame.size.width - self.sumCellWidth - ((layoutAttributes.count - 1) * _betweenOfCell)) / 2;
            for (UICollectionViewLayoutAttributes * attributes in layoutAttributes)
            {
                CGRect nowFrame = attributes.frame;
                nowFrame.origin.x = nowWidth;
                attributes.frame = nowFrame;
                nowWidth += nowFrame.size.width + self.betweenOfCell;
            }
            self.sumCellWidth = 0.0;
            [layoutAttributes removeAllObjects];
            break;
        case AlignWithRight:
            nowWidth = self.collectionView.frame.size.width - self.sectionInset.right;
            for (NSInteger index = layoutAttributes.count - 1 ; index >= 0 ; index-- )
            {
                UICollectionViewLayoutAttributes * attributes = layoutAttributes[index];
                CGRect nowFrame = attributes.frame;
                nowFrame.origin.x = nowWidth - nowFrame.size.width;
                attributes.frame = nowFrame;
                nowWidth = nowWidth - nowFrame.size.width - _betweenOfCell;
            }
            self.sumCellWidth = 0.0;
            [layoutAttributes removeAllObjects];
            break;
    }
}





@end

偷偷写bug.jpg
雪碧.gif

拿来使用

        BaseTypesettingFlowLayout *flowLayout = [[BaseTypesettingFlowLayout alloc] initWithType:AlignWithRight betweenOfCell:RATIOA(10) sectionInsetCell:UIEdgeInsetsMake(0, 0, 0, RATIOA(15))];
        _collectionView = [[UICollectionView alloc] initWithFrame:CGRectZero collectionViewLayout:flowLayout];