layer.cornerRadius与NSLayoutConstraints（swift 3）不兼容

Question

下面是我的个人资料视图约束，视图渲染效果很好，但宽度始终为零。因此，最终约束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？

Answer 1

profileImageView.frame.width为零，因为它的帧尚未计算。在profileImageView覆盖layoutSubviews方法内：

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

或者，如果您正在使用视图控制器，请覆盖viewDidLayoutSubviews方法：

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

Answer 2

UIViewController尚未布局，并且没有规模。假设这是在viewDidLayoutSubviews子类中，您可以将角半径代码放在override func viewDidLayoutSubviews() { profileImageView.layer.cornerRadius = (profileImageView.frame.width / 2) } 内：

int hitCount, missCount, evictionCount;
int s, E, b;