layer.cornerRadius未与NSLayoutConstraints协同工作( with 3)

Question

下面是我的配置文件视图约束，视图呈现得很好，但是宽度始终返回零。因此，最后一个约束profileImageView.layer.cornerRadius = (profile.frame.width / 2)每次都返回零。

    profileImageView.translatesAutoresizingMaskIntoConstraints = false


    addConstraint(NSLayoutConstraint(item: profileImageView, attribute: .width, relatedBy: .equal, toItem: containerView, attribute: .width, multiplier: 0.125, constant: 0))


    addConstraint(NSLayoutConstraint(item: profileImageView, attribute: .height, relatedBy: .equal, toItem: containerView, attribute: .width, multiplier: 0.125, constant: 0))




    addConstraint(NSLayoutConstraint(item: profileImageView, attribute: .centerY, relatedBy: .equal, toItem: containerView, attribute: .centerY, multiplier: 1, constant: 0))

    addConstraint(NSLayoutConstraint(item: profileImageView, attribute: .centerX, relatedBy: .equal, toItem: containerView, attribute: .centerX, multiplier: 0.25, constant: 0))

    profileImageView.layer.cornerRadius = (profileImageView.frame.width / 2)

有什么建议吗？

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Answer 1

profileImageView.frame.width是零，因为它的帧还没有计算。在profileImageView重写layoutSubviews方法中：

override func layoutSubviews() {
    super.layoutSubviews()
    layer.cornerRadius = bounds.width / 2.0
}

或者，如果使用的是视图控制器，请重写viewDidLayoutSubviews方法：

override func viewDidLayoutSubviews() {
    super.viewDidLayoutSubviews()
    profileImageView.layer.cornerRadius = profileImageView.bounds.width / 2.0
}

Answer 2

profileImageView还没有布局，也没有尺寸。假设这是在UIViewController子类中，您可以将角半径代码放在viewDidLayoutSubviews中。

override func viewDidLayoutSubviews() {
    profileImageView.layer.cornerRadius = (profileImageView.frame.width / 2)
}