移至上一个屏幕时，如何摆脱更改导航栏颜色的延迟？

Question

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

    self.navigationController?.navigationBar.setBackgroundImage(UIImage(), for: .default)
    self.navigationController?.navigationBar.shadowImage = UIImage()
    self.navigationController?.navigationBar.isTranslucent = true
    self.tabBarController?.tabBar.isHidden = true
}

override func viewWillDisappear(_ animated: Bool) {
    super.viewWillDisappear(animated)
    self.navigationController?.navigationBar.setBackgroundImage(nil, for: .default)
    self.navigationController?.navigationBar.shadowImage = nil
    self.tabBarController?.tabBar.isHidden = false
}

点击后退（NavBar）后，我看到一个延迟（1.5 s）。我不明白为什么。

Answer 1

Func willMove from docs可以帮助我。