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  • Masonry 添加约束要注意顺序

    对一个视图添加约束,其依赖的约束必须先已经存在,不能依赖该代码后的约束,否则造成不可预料的结果,如下代码能达到预期效果

    - (void)makeConstraints {
        __weak typeof(self) weakSelf = self;
    
        [self.photoMoreButton mas_makeConstraints:^(MASConstraintMaker *make) {
            make.right.equalTo(weakSelf.photoButton).with.offset(-6);
            make.centerY.equalTo(weakSelf.photoButton);
            make.width.and.height.equalTo(@16);
        }];
        
        [self.photoImageView mas_makeConstraints:^(MASConstraintMaker *make) {
            make.centerY.equalTo(weakSelf.photoButton);
            make.right.equalTo(weakSelf.photoMoreButton.mas_left);
            make.width.and.height.equalTo(@64);
        }];
    }

    但是如果颠倒添加约束的顺序,如下

    - (void)makeConstraints {
        __weak typeof(self) weakSelf = self;
     
        [self.photoImageView mas_makeConstraints:^(MASConstraintMaker *make) {
            make.centerY.equalTo(weakSelf.photoButton);
            make.right.equalTo(weakSelf.photoMoreButton.mas_left);
            make.width.and.height.equalTo(@64);
        }];
    
         [self.photoMoreButton mas_makeConstraints:^(MASConstraintMaker *make) {
            make.right.equalTo(weakSelf.photoButton).with.offset(-6);
            make.centerY.equalTo(weakSelf.photoButton);
            make.width.and.height.equalTo(@16);
        }];
    }

    则得到的效果如下图

    添加约束时 photoImageView 依赖于 photoMoreButton,而当时 photoMoreButton 的约束还未设置,所以导致后面不正确的结果,使用Masonry时要注意这点!

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  • 原文地址:https://www.cnblogs.com/mforestlaw/p/5613913.html
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