一、准备

1.UICollectionView Left Aligned Layout

• 一款UICollectionView居左显示的约束
  点击下载_UICollectionView Left Aligned Layout

二、工程目录

三、自定义UICollectionViewCell

CollectionViewCell.h 创建UILabel属性,用来传值

#import <UIKit/UIKit.h>
@interface CollectionViewCell : UICollectionViewCell
@property (nonatomic, strong) UILabel *titleLB;;
@end

CollectionViewCell.m 创建显示文本视图

• 此处titleLB文字大小要和计算的文字大小相同

#import "CollectionViewCell.h"
@implementation CollectionViewCell

- (instancetype)initWithFrame:(CGRect)frame{
    self = [super initWithFrame:frame];
    if (self) {
        self.backgroundColor = [UIColor colorWithRed:251/255.0 green:74/255.0 blue:71/255.0 alpha:1];
        self.layer.cornerRadius = 3;
        self.layer.masksToBounds = YES;
        self.layer.borderColor = [UIColor lightTextColor].CGColor;
        self.layer.borderWidth = 0.5;
        
        [self createSubViews];
    }
    return self;
}

- (void)createSubViews{
    _titleLB = [[UILabel alloc] initWithFrame:CGRectMake(0, 0, self.frame.size.width, self.frame.size.height)];
    //_titleLB.backgroundColor = [UIColor yellowColor];
    _titleLB.textColor = [UIColor whiteColor];
    _titleLB.textAlignment = NSTextAlignmentCenter;
    _titleLB.font = [UIFont systemFontOfSize:14];
    [self.contentView addSubview:_titleLB];
}
@end

四、在ViewController中创建UICollectionView

ViewController.h

#import <UIKit/UIKit.h>
@interface ViewController : UIViewController

@end

ViewController.m

#import "ViewController.h"
#import "UICollectionViewLeftAlignedLayout.h"
#import "CollectionViewCell.h"
@interface ViewController ()<UICollectionViewDataSource, UICollectionViewDelegate, UICollectionViewDelegateFlowLayout>

@end

@implementation ViewController{
    NSArray *_allTextArr;
}

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    self.view.backgroundColor = [UIColor whiteColor];
    [self initailData];
    [self createMianView];
}

/**
 *  虚拟数据
 */
- (void)initailData{
    _allTextArr = @[@"19朵玫瑰礼盒", @"19朵红玫瑰礼盒+百合", @"33朵红玫瑰礼盒", @"33朵红玫瑰礼盒(三世情缘)", @"33朵香槟玫瑰礼盒(生日推荐)", @"38朵红玫瑰心连心礼盒(一见倾心)", @"19朵红玫瑰礼盒(热卖推荐)", @"19朵粉玫瑰礼盒(热卖推荐)", @"19朵混色玫瑰礼盒"];
}

/**
 *  创建视图
 */
- (void)createMianView{
    //居左约束
     UICollectionViewLeftAlignedLayout *leftAlignedLayout = [[UICollectionViewLeftAlignedLayout alloc] init];
    leftAlignedLayout.minimumLineSpacing = 10;                          //最小行间距
    leftAlignedLayout.minimumInteritemSpacing = 10;                     //最小列间距
    leftAlignedLayout.sectionInset = UIEdgeInsetsMake(20, 20, 20, 20);  //网格上左下右间距
    
    //网格
    UICollectionView *mainCollectionView = [[UICollectionView alloc] initWithFrame:CGRectMake(0, 0, self.view.frame.size.width, self.view.frame.size.height) collectionViewLayout:leftAlignedLayout];
    mainCollectionView.backgroundColor = [UIColor whiteColor];
    mainCollectionView.dataSource = self;
    mainCollectionView.delegate = self;
    [self.view addSubview:mainCollectionView];
    [mainCollectionView registerClass:[CollectionViewCell class] forCellWithReuseIdentifier:@"cell"];
}

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

#pragma mark -UICollectionViewDataSource
//item内容
- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath{
    CollectionViewCell *cell = (CollectionViewCell *)[collectionView dequeueReusableCellWithReuseIdentifier:@"cell" forIndexPath:indexPath];
    cell.titleLB.text = [NSString stringWithFormat:@"%@", [_allTextArr objectAtIndex:indexPath.row]];
    return cell;
}

//Section中item数量
- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section{
    return _allTextArr.count;
}

#pragma mark -UICollectionViewDelegate
//点击item触发方法
- (void)collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath:(NSIndexPath *)indexPath{
    
}

#pragma mark -UICollectionViewDelegateFlowLayout
//设置每个item的尺寸
- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath{
    NSString *textString = [_allTextArr objectAtIndex:indexPath.row];
    CGFloat cell_width = [self settingCollectionViewItemWidthBoundingWithText:textString];
    return CGSizeMake(cell_width, 30);
}

//计算文字宽度
- (CGFloat)settingCollectionViewItemWidthBoundingWithText:(NSString *)text{
    //1,设置内容大小  其中高度一定要与item一致,宽度度尽量设置大值
    CGSize size = CGSizeMake(MAXFLOAT, 20);
    //2,设置计算方式
    //3,设置字体大小属性   字体大小必须要与label设置的字体大小一致
    NSDictionary *attributeDic = @{NSFontAttributeName: [UIFont systemFontOfSize:14]};
    CGRect frame = [text boundingRectWithSize:size options: NSStringDrawingUsesLineFragmentOrigin attributes:attributeDic context:nil];
    //4.添加左右间距
    return frame.size.width + 15;
}

五、运行效果