Masonry一个居中布局

效果如图：

居中.gif

前言

需求是只有一个，两个，三个item的时候居中，超过限制宽度的时候做成从左往右的滚动效果。

分析

要求居中，所以我们给一个大的容器，让其居中即可，高度确定，宽度根据子视图自适应，因此可以考虑用UIScrollview的自适应。

  
    [self.scrollView1 mas_makeConstraints:^(MASConstraintMaker *make) {
        make.height.mas_equalTo(FixH(59));
        make.centerX.mas_equalTo(0);
        make.top.mas_equalTo(SafeAreaTopHeight);
    }];

代码

用UIScrollview做容器

-(instancetype)init{
    self = [super init];
    if (self) {
        
        UIScrollView *scrollView = UIScrollView.new;
        self.scrollView = scrollView;
        
        self.scrollView.showsVerticalScrollIndicator = NO;
        self.scrollView.showsHorizontalScrollIndicator = NO;
        scrollView.backgroundColor = [UIColor whiteColor];
        [self addSubview:scrollView];
       
        [self.scrollView mas_makeConstraints:^(MASConstraintMaker *make) {
            make.edges.equalTo(self);
        }];
        
        self.count = 5;
    }
    return self;
}

UIScrollView的宽度自适应需要一个容器，Masonry的GitHub示例中高度自适应也是如此。

- (void)generateContent {
   
    
    [self.contentView removeFromSuperview];
    
    //scrollView 需要一个撑满的容器
    UIView* contentView = UIView.new;
    
    [self.scrollView addSubview:contentView];
    
    [contentView mas_makeConstraints:^(MASConstraintMaker *make) {
        make.edges.equalTo(self.scrollView);
        make.height.equalTo(self.scrollView);
    }];
    
    self.contentView = contentView;
   
    LXScrollViewItem *lastButton = nil;
    
    
    CGFloat totalWidth = FixW(30);
    
    CGFloat space = FixW(30);
    
    for (int i = 0; i < self.count; i++) {
        LXScrollViewItem *view = [[LXScrollViewItem alloc]init];
        
        view.backgroundColor = [UIColor whiteColor];
        
        [_contentView addSubview:view];
        
        view.icon.image = [UIImage imageNamed:@"头像"];
        
        NSString *str = @"忒修斯";
        
        view.textLabel.text = str;
        
        //计算宽度
        CGFloat width = [str sizeWithFont:[UIFont systemFontOfSize:11 weight:UIFontWeightMedium] maxSize:CGSizeMake(CGFLOAT_MAX, FixH(13))].width;
        
        if (width <= FixW(32)) {
            
            width = FixW(32);
            
        }
        [view mas_makeConstraints:^(MASConstraintMaker *make) {
            
            make.top.mas_equalTo(0);
            if (!lastButton) {
                make.left.mas_equalTo(space);
            }else{
                make.left.mas_equalTo(lastButton.mas_right).offset(space);
            }
            make.width.mas_equalTo(width);
            make.height.equalTo(self.contentView);
        }];
        
        totalWidth += (width + space);
        
        lastButton = view;
    }

    //容器右侧根据子视图确定
    [self.contentView mas_updateConstraints:^(MASConstraintMaker *make) {
        make.right.mas_equalTo(lastButton.mas_right).offset(space);
    }];
    
    
    //限制滚动，设置内容区域
    if (totalWidth >= kScreenWidth - space) {
        self.scrollView.scrollEnabled = YES;
        [self mas_updateConstraints:^(MASConstraintMaker *make) {
            make.width.mas_equalTo(kScreenWidth - space);
        }];
    }else{
        self.scrollView.scrollEnabled = NO;
        
        [self mas_updateConstraints:^(MASConstraintMaker *make) {
            make.width.mas_equalTo(totalWidth);
        }];
    }
    
}

demo地址:居中自适应布局