UIView动画不是动画

Question

我想隐藏徽标(图像视图)和显示搜索栏时，animately.But的代码运行被隐藏的动画立即工程(它必须在2秒内).search栏在2秒内可见的animately.what在此代码中是错误的？

  UIView.transition(with: self.logo, duration: 2, options: .transitionCrossDissolve, animations: {
            self.logo.isHidden = true
        }) { (completed) in
            UIView.transition(with: self.searchBar, duration: 2, options: .transitionCrossDissolve, animations: {
                self.searchBar.isHidden = false
            },completion: nil)
        }

Answer 1

正如注释中所指出的，您需要使用alpha属性来创建外观/消失效果。因此，您的代码将如下所示：

UIView.transition(with: self.logo, duration: 2, options: .transitionCrossDissolve, animations: {
            self.logo.alpha = 0
        }) { (completed) in
            UIView.transition(with: self.searchBar, duration: 2, options: .transitionCrossDissolve, animations: {
                self.searchBar.alpha = 1
            },completion: nil)
        }

正如这里的苹果文档中所说的：https://developer.apple.com/documentation/uikit/uiview，

UIView类的以下属性是可设置动画的:帧、边界、中心、变换、alpha、背景色