swift - 启动屏幕消失后和 viewDidAppear() 方法运行之前出现奇怪的动画 'lag'

Question

启动屏幕关闭后，我的应用程序的 Logo 和标题(它们位于容器中)应该更靠近屏幕顶部。在关闭启动屏幕和 viewDidAppear 方法之间，我的容器在后台出现奇怪的“闪烁”。正如你所看到的，我正在使用 snapkit，但它应该与问题无关。这是我的代码:

class WelcomeScreenViewController: UIViewController {

var welcomeScreenView: WelcomeScreenView {
    return view as! WelcomeScreenView
}

override func loadView() {
    let contentView = WelcomeScreenView(frame: .zero)
    view = contentView

}

override func viewDidLoad() {
    super.viewDidLoad()
    self.welcomeScreenView.checkWeatherButton.transform = CGAffineTransform(translationX: 0, y: 200)
    self.welcomeScreenView.checkWeatherButton.addTarget(self, action: #selector(showCityChoiceVC), for: .touchUpInside)
    navigationController?.isNavigationBarHidden = true
}

override func viewDidAppear(_ animated: Bool) {
    super.viewDidAppear(animated)

    self.welcomeScreenView.appNameLogoContainerVerticalConstraint?.isActive = false
    self.welcomeScreenView.appNameLogoContainer.snp.makeConstraints({ (make) in
        make.top.equalTo(self.welcomeScreenView).offset(100)
    })

    UIView.animate(withDuration: 0.5, delay: 0, usingSpringWithDamping: 0.7, initialSpringVelocity: 0.5, options: [], animations: {
        self.welcomeScreenView.layoutIfNeeded()
        self.welcomeScreenView.checkWeatherButton.transform = CGAffineTransform(translationX: 0, y: 0)
    }, completion: nil)

}

@objc private func showCityChoiceVC() {
    self.navigationController?.pushViewController(RegisterViewController(), animated: true)
}

Answer 1

闪烁来自于在viewDidAppear中设置约束。请改用 viewWillAppear 或 viewDidLoad。当您的 View 实际出现在屏幕上时，将调用viewDidAppear。因此，发生的任何更改对于用户来说都是可见的。