如何用动画改变导航栏的背景图片？

Question

我正在使用我们所有人都知道的动画，动画以更改导航栏的背景图像，延迟时间很短，以将其从半透明（我将其设为默认）更改为（蓝色主题）。

UIView.animate(withDuration:0.5, 
               delay: 0, 
               option: UIViewAnimationOptions.curveEaseOut, 
               animations: {
        self.navigationController?.navigationBar.setBackgroundImage(UIImage(), for: .default)
        self.navigationController?.navigationBar.shadowImage = UIImage()
    }, completion: nil)

但是动画没有效果，但是导航栏的背景图片变成功了，不知道为什么！！

有什么想法吗？

Answer 1

您需要在动画块中调用layoutIfNeeded()，例如

UIView.animate(withDuration: 0.5, delay: 0, options: .curveEaseOut, animations: { 
    self.navigationController?.navigationBar.barTintColor = .blue
    self.navigationController?.navigationBar.layoutIfNeeded()
}, completion: nil)

更改背景图片的更新

这段代码对我有用：

let animation = CATransition()
animation.duration = 0.5
animation.timingFunction = CAMediaTimingFunction(name: kCAMediaTimingFunctionEaseOut)
animation.type = kCATransitionFade

navigationController?.navigationBar.layer.add(animation, forKey: nil)

UIView.animate(withDuration: 0.5, delay: 0, options: .curveEaseOut, animations: {
    self.navigationController?.navigationBar.setBackgroundImage(UIImage(named: "your-image-name"), for: .default)
}, completion: nil)