iOS-UICollectionView一行可以居左或居中，居右自适应宽度显示多个Item

爱被打了一巴掌 2023-10-18 19:21 104阅读 0赞

近来需要做一个需求，就是可以输入新建多个标签，标签高度固定，但宽度不固定且个数不固定，效果图如下：

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L01pbmdnZVFpbmdjaHVu_size_16_color_FFFFFF_t_70][]

因此初步设想：使用UICollectionView的item自适应宽度，方法如下：

#import "TestCollectionCell.h"
    
    @interface TestCollectionCell()
    
    @property(nonatomic,weak)UILabel *yardLab;
    
    @end
    
    @implementation TestCollectionCell
    
    - (instancetype) initWithFrame:(CGRect)frame {
        if (self = [super initWithFrame:frame]) {
            [self setSubView];
        }
        return self;
    }
    
    - (void)setSubView{
        CGFloat labH = 30.0;
        UILabel *yardLab = [[UILabel alloc] init];
        yardLab.textAlignment = NSTextAlignmentCenter;
        self.yardLab = yardLab;
        yardLab.layer.masksToBounds = YES;
        yardLab.layer.cornerRadius = labH/2.0;
        yardLab.backgroundColor = YardsColor;
    //    yardLab.text = @"22222222343423";
        yardLab.font = SET_FONT(14.0);
        [self.contentView addSubview:yardLab];
        [yardLab mas_makeConstraints:^(MASConstraintMaker *make) {
            make.left.right.top.equalTo(self.contentView);
            make.height.mas_equalTo(@(labH));
        }];
        yardLab.userInteractionEnabled = NO;
        //删除按钮用自身
        UITapGestureRecognizer *tapGestureRecognizer = [[UITapGestureRecognizer alloc]initWithTarget:self action:@selector(singleTap:)];
        [tapGestureRecognizer setNumberOfTapsRequired:1];
        [yardLab addGestureRecognizer:tapGestureRecognizer];
        
        CGFloat btnH = 18.0;
        UIButton *deleteBtn = [UIButton buttonWithType:UIButtonTypeCustom];
        deleteBtn.backgroundColor = [UIColor redColor];
        self.deleteBtn = deleteBtn;
        deleteBtn.hidden = YES;
        deleteBtn.enabled = NO;
        deleteBtn.layer.masksToBounds = YES;
        deleteBtn.layer.cornerRadius = btnH/2.0;
        [deleteBtn setBackgroundImage:[UIImage imageNamed:@"yard_delete"] forState:UIControlStateNormal];
    //    [deleteBtn addTarget:self action:@selector(managerAction:) forControlEvents:UIControlEventTouchUpInside];
        [self.contentView addSubview:deleteBtn];
        [deleteBtn mas_makeConstraints:^(MASConstraintMaker *make) {
            make.width.height.mas_equalTo(@(btnH));
            make.right.equalTo(yardLab.mas_right).offset(btnH/3.0);
            make.top.mas_equalTo(@(-btnH/2.0));
        }];
    }
    
    #pragma mark — 实现自适应文字宽度的关键步骤:item的layoutAttributes
    - (UICollectionViewLayoutAttributes *)preferredLayoutAttributesFittingAttributes:(UICollectionViewLayoutAttributes *)layoutAttributes {
        [self setNeedsLayout];
        [self layoutIfNeeded];
        CGSize size = [self.contentView systemLayoutSizeFittingSize:layoutAttributes.size];
        CGRect cellFrame = layoutAttributes.frame;
        cellFrame.size.width = size.width + 16;
        layoutAttributes.frame = cellFrame;
        return layoutAttributes;
    }

过程发现两个问题：

1、如果使用button，如下方法不能计算出宽度，要使用UILabel

2、如果只有一个item，会发现居中显示，但是并未发现UICollectionView有类似UILabel居左，居中，居右显示item的属性方法，效果图如下：

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L01pbmdnZVFpbmdjaHVu_size_16_color_FFFFFF_t_70 1][]

解决办法如下：

//collectionView的item只剩下一个时自动左对齐
        SEL sel = NSSelectorFromString(@"_setRowAlignmentsOptions:");
        if ([yardsCollection.collectionViewLayout respondsToSelector:sel]) {
            ((void(*)(id,SEL,NSDictionary*)) objc_msgSend)(yardsCollection.collectionViewLayout,sel, @{@"UIFlowLayoutCommonRowHorizontalAlignmentKey":@(NSTextAlignmentLeft),@"UIFlowLayoutLastRowHorizontalAlignmentKey" : @(NSTextAlignmentLeft),@"UIFlowLayoutRowVerticalAlignmentKey" : @(NSTextAlignmentCenter)});
        }

最终效果：

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L01pbmdnZVFpbmdjaHVu_size_16_color_FFFFFF_t_70 2][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L01pbmdnZVFpbmdjaHVu_size_16_color_FFFFFF_t_70 3][]

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L01pbmdnZVFpbmdjaHVu_size_16_color_FFFFFF_t_70]: https://img-blog.csdnimg.cn/20190604145727800.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L01pbmdnZVFpbmdjaHVu,size_16,color_FFFFFF,t_70
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L01pbmdnZVFpbmdjaHVu_size_16_color_FFFFFF_t_70 1]: https://img-blog.csdnimg.cn/20190604150303971.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L01pbmdnZVFpbmdjaHVu,size_16,color_FFFFFF,t_70
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L01pbmdnZVFpbmdjaHVu_size_16_color_FFFFFF_t_70 2]: https://img-blog.csdnimg.cn/20190604151217191.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L01pbmdnZVFpbmdjaHVu,size_16,color_FFFFFF,t_70
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L01pbmdnZVFpbmdjaHVu_size_16_color_FFFFFF_t_70 3]: https://img-blog.csdnimg.cn/2019060415123960.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L01pbmdnZVFpbmdjaHVu,size_16,color_FFFFFF,t_70