[英]How to persist navigationItem.titleView between screen?
我正在使用NavigationController来管理三个屏幕。 所有三个屏幕共享一个共同的图像作为标题。 我在每个VC的viewWillAppear中设置图像如下:
self.navigationItem.titleView = myImageView
问题是每当按下/弹出屏幕,导航动画并且新图像将来自右侧或左侧时。 我希望图像能够持续存在并且保持在中间没有动画。
有没有办法禁用这个动画?
只有在viewWillAppear
放置/设置titleView代码时,它才是可重现的。 它正在移动,因为viewWillAppear在第四次(push)和后退(pop)两种操作中都被调用。 将其设置为viewDidLoad
,它将解决此问题
override fun viewDidLoad() {
super.viewDidLoad()
self.navigationItem.titleView = myImageView
}
这个问题的另一个替代解决方案是
var isViewDidLoadCalled = false
override fun viewDidLoad() {
super.viewDidLoad()
isViewDidLoadCalled = true
}
override fun viewWillAppear(_ animated: Bool) {
super. viewWillAppear(animated)
if (isViewDidLoadCalled) {
self.navigationItem.titleView = myImageView
isViewDidLoadCalled = false
}
}
我建议使用viewDidLoad来设置你的titleView
另一个困难但可行的解决方案是
您需要使用UINavigationController委托方法来查明何时显示UIViewController 。 然后对于每个UIViewController,需要创建一个类似于isInitialized属性的布尔变量,它可以帮助您确定何时将UIViewController压入堆栈,或者何时将其显示在下一个视图控制器的后面。
你的FirstViewController:
func navigationController(_ navigationController: UINavigationController, willShowViewController viewController: UIViewController, animated: Bool) {
if viewController == self {
if self.isInitialized {
var navigationBarAnimation = CATransition()
navigationBarAnimation.duration = 1.5
navigationBarAnimation.timingFunction = CAMediaTimingFunction(name: kCAMediaTimingFunctionEaseIn)
navigationBarAnimation.type = kCATransitionFade
navigationBarAnimation.subtype = kCATransitionFade
navigationBarAnimation.removedOnCompletion = true
self.navigationController?.navigationBar?.layer?.addAnimation(navigationBarAnimation, forKey: nil)
} else {
self.isInitialized = true;
}
}
}
func navigationController(_ navigationController: UINavigationController, didShowViewController viewController: UIViewController, animated: Bool) {
if viewController == self {
if self.isInitialized {
self.navigationController?.navigationBar?.layer?.removeAllAnimations()
}
}
}
你的SecondViewController:
func navigationController(_ navigationController: UINavigationController, willShowViewController viewController: UIViewController, animated: Bool) {
if viewController == self {
if !self.isInitialized {
var navigationBarAnimation = CATransition()
navigationBarAnimation.duration = 1.5
navigationBarAnimation.timingFunction = CAMediaTimingFunction(name: kCAMediaTimingFunctionEaseIn)
navigationBarAnimation.type = kCATransitionFade
navigationBarAnimation.subtype = kCATransitionFade
navigationBarAnimation.removedOnCompletion = true
self.navigationController?.navigationBar?.layer?.addAnimation(navigationBarAnimation, forKey: nil)
self.isInitialized = true;
}
}
}
func navigationController(_ navigationController: UINavigationController, didShowViewController viewController: UIViewController, animated: Bool) {
if viewController == self {
if self.isInitialized {
self.navigationController?.navigationBar?.layer?.removeAllAnimations()
}
}
}
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