这可以使用UIView的过渡动画来完成.isHighlighted
属性不可设置动画并不重要,因为它会转换整个视图.
UIView.transition(with: button,
duration: 4.0,
options: .transitionCrossDissolve,
animations: { button.isHighlighted = true },
completion: nil)
[UIView transitionWithView:button
duration:4.0
options:UIViewAnimationOptionTransitionCrossDissolve
animations:^{ button.highlighted = YES; }
completion:nil];