Question

当转到第二页时，我试图在0.33秒内从左侧向后滑动后退按钮。现在，即使将播放时间减慢到2秒以澄清视觉效果，动画似乎也没有这样做。想知道是否有人可以告诉我我在代码中做错了什么以及如何纠正它？

说出来，我可能只是误解了动画的某些方面。

func addBackButton() {
        let backButton = UIButton(type: .custom)
        backButton.setImage(#imageLiteral(resourceName: "backArrow"), for: .normal)
        backButton.setTitle("", for: .normal)
        backButton.setTitleColor(backButton.tintColor, for: .normal)
        backButton.addTarget(self, action: #selector(backAction), for: .touchUpInside)
        let backBarButtonItem = UIBarButtonItem(customView: backButton)
        backBarButtonItem.customView?.transform = CGAffineTransform(translationX: -backButton.frame.width, y: 0)
        navigationItem.leftBarButtonItems?.insert(backBarButtonItem, at: 0)
        UIView.animate(withDuration: 2, delay: 0.5, animations: {
            backBarButtonItem.customView?.transform = CGAffineTransform(translationX: 2 * backButton.frame.width, y: 0)
        })
    }

Answer 1

您只需要将此自定义按钮放在containerView内，并将该containerView设置为UIBarButtonItem's自定义视图。您的设置将如下所示，

let containerFrame = CGRect(origin: .zero, size: CGSize(width: 44.0, height: 44.0))
let container = UIView(frame: containerFrame)

let buttonFrame = CGRect(origin: CGPoint(x: -100, y: 0), size: CGSize(width: 44, height: 44))  
let backButton = UIButton(frame: buttonFrame)
backButton.setImage(#imageLiteral(resourceName: "backArrow"), for: .normal)
backButton.setTitle("", for: .normal)
backButton.setTitleColor(backButton.tintColor, for: .normal)
backButton.addTarget(self, action: #selector(backAction), for: .touchUpInside)
container.addSubview(backButton)

let backBarButtonItem = UIBarButtonItem(customView: container)
UIView.animate(withDuration: 2, delay: 0.5, animations: {
    backButton.transform = CGAffineTransform(translationX: 2 * backButton.frame.width, y: 0)
})

您可以检查为什么需要将自定义button包装在另一个UIView here中。

Answer 2

UIView不是UINavigationItem.setLeftBarButtonItems(_:animated:)子类是有原因的。如果这是您想要的效果（平台一致性说您应该使用backButton），则应该将leftBarButtonItem添加到视图层次结构中，对其进行动画处理，然后将其设置为navigationController?.navigationBar.addSubview(backButton) // layout back button in it's final spot here, either via constraints or frame math backButton.transform = CGAffineTransform(translationX: -(button.bounds.width + leadingSpacing), translationY: 0.0) UIView.animate(duration: 0.3, animations: { backButton.transform = .identity } { completed in self.navigationItem.leftBarButtonItem = UIBarButtonItem }在完成块中。

请记住，您可能必须将其添加到导航栏视图层次结构中，以便它显示在其顶部。这种方法还意味着您基本上是在复制导航栏的布局代码，并且必须弄清楚它应该在哪里结束。

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从左侧滑动UIBarButtonItem

2 个答案: