向底部锚添加约束是向超级视图底部添加约束

Posted 2023-03-15

【中文标题】向底部锚添加约束是向超级视图底部添加约束

【英文标题】：Adding constraint to bottom anchor is adding to constraint to superview bottom

【发布时间】：2019-08-25 16:47:45

【问题描述】：

我正在尝试将 UIImageview 的约束添加到安全区域布局指南的前导、尾随、顶部和底部，如下所示：

    if (@available(ios 11.0, *)) 
        [[self.view.safeAreaLayoutGuide.topAnchor constraintEqualToAnchor:self.bgImageView.safeAreaLayoutGuide.topAnchor] setActive:true];
        [[self.view.safeAreaLayoutGuide.bottomAnchor constraintEqualToAnchor:self.bgImageView.safeAreaLayoutGuide.bottomAnchor] setActive:true];
        [[self.view.safeAreaLayoutGuide.leadingAnchor constraintEqualToAnchor:self.bgImageView.safeAreaLayoutGuide.leadingAnchor] setActive:true];
        [[self.view.safeAreaLayoutGuide.trailingAnchor constraintEqualToAnchor:self.bgImageView.safeAreaLayoutGuide.trailingAnchor] setActive:true];
      

但是，实际结果是：

这可能是什么原因？

【参考方案1】：

你可以使用

NSLayoutConstraint.activate([
        bgImageView.topAnchor.constraint(equalTo: self.view.safeAreaLayoutGuide.topAnchor),
        bgImageView.leadingAnchor.constraint(equalTo: self.view.safeAreaLayoutGuide.leadingAnchor),
        bgImageView.trailingAnchor.constraint(equalTo: self.view.safeAreaLayoutGuide.trailingAnchor),
        bgImageView.bottomAnchor.constraint(equalTo: self.view.safeAreaLayoutGuide.bottomAnchor)
        ])