Swift 3/4 如何为 UIImageView 的 contentMode 设置动画

问题描述

我的目标是当我点击按钮切换 contentMode: scaleAspectFit &scaleAspectFill 使用动画.

 @IBAction func toggleContentModeAction(_ sender: UIButton) {sender.isSelected = !sender.isSelected如果 sender.isSelected {UIView.animate(withDuration: 0.3) {self.popImageView.contentMode = .scaleAspectFitself.view.layoutIfNeeded()}}别的 {UIView.animate(withDuration: 0.3) {self.popImageView.contentMode = .scaleAspectFillself.view.layoutIfNeeded()}}}

但对我的目标没有效果.请帮我解决，感谢柬埔寨.

解决方案

contentMode 本身不是可动画的属性.但是您可以使用

My goal is when I click on button to toggle contentMode: scaleAspectFit & scaleAspectFill with animation.

    @IBAction func toggleContentModeAction(_ sender: UIButton) {
    sender.isSelected = !sender.isSelected
    if sender.isSelected {
        UIView.animate(withDuration: 0.3) {
            self.popImageView.contentMode = .scaleAspectFit
            self.view.layoutIfNeeded()
        }
    }else {
        UIView.animate(withDuration: 0.3) {
            self.popImageView.contentMode = .scaleAspectFill
            self.view.layoutIfNeeded()
        }
    }
}

but no effective to my goal. Please fix for me, thanks from Cambodia.

解决方案

The contentMode, itself, is not an animatable property. But you can animated between two different renditions of a view with transition(with:duration:options:animations:completion:), e.g.

@IBAction func didTapButton(_ sender: UIButton) {
    let contentMode: UIViewContentMode = imageView.contentMode == .scaleAspectFill ? .scaleAspectFit : .scaleAspectFill

    UIView.transition(with: imageView, duration: 1, options: .transitionCrossDissolve, animations: {
        self.imageView.contentMode = contentMode
    }, completion: nil)
}

That yields:

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