问题描述
在我的应用中，当iOS系统暗模式设置更改时，我需要进行一些自定义UI更改.根据 https://developer.apple.com/videos/play/wwdc2019/214/明确提到要实现traitCollectionDidChange并使用hasDifferentColorAppearance(comparedTo:)比较以前和当前的特征集.
In my app I need to make some custom UI changes when iOS system dark mode settings change. According to https://developer.apple.com/videos/play/wwdc2019/214/ it's explicitly mentioned to implement traitCollectionDidChange and compare the previous and current trait collection using hasDifferentColorAppearance(comparedTo:).
文档说:
我在视图控制器的子类中实现了
In my view controller's subclass I implemented
override func traitCollectionDidChange(_ previousTraitCollection: UITraitCollection?) {
super.traitCollectionDidChange(previousTraitCollection)
if #available(iOS 13.0, *),
self.traitCollection.hasDifferentColorAppearance(comparedTo: previousTraitCollection) {
let isSameUserInterfaceStyle = (self.traitCollection.userInterfaceStyle == previousTraitCollection?.userInterfaceStyle)
let isSameAcessibilityContrast = (self.traitCollection.accessibilityContrast == previousTraitCollection?.accessibilityContrast)
// do custom stuff
}
}
但是在某些情况下，isSameUserInterfaceStyle和isSameAcessibilityContrast都将评估为true，如果hasDifferentColorAppearance(comparedTo:)也返回true，我没想到.我不喜欢解决Apple建议的API使用问题，但另一方面，如果userInterfaceStyle实际没有更改，我不想对UI进行不必要的更改.因此，我不确定是否应该依靠hasDifferentColorAppearance(comparedTo:)的结果还是仅比较两个特征集的userInterfaceStyle就足够了.
But in some cases both isSameUserInterfaceStyle and isSameAcessibilityContrast evaluate to true which I did not expect if hasDifferentColorAppearance(comparedTo:) also returns true.I'm not a fan of working around Apple's suggested API usage but on the other hand I don't want to make unnecessary changes to my UI if userInterfaceStyle did not actually change. So I'm not sure if I should rely on the result of hasDifferentColorAppearance(comparedTo:) or if it suffices to just compare userInterfaceStyle of both trait collections.
推荐答案
对两个特征集的更深入研究表明，当前特征集的userInterfaceLevel属性设置为.elevated.其他所有属性均相同. userInterfaceLevel值的更改是由于将另一个视图控制器显示为弹出框而引起的.考虑到这一事实，我需要另外检查self.traitCollection.userInterfaceStyle != previousTraitCollection?.userInterfaceStyle以确定暗/亮外观是否确实发生了变化.
A deeper investigation of both trait collections brought to light that the current trait collection's userInterfaceLevel property was set .elevated. All other properties were identical. The change in userInterfaceLevel's value was caused by presenting another view controller as a popover. Considering this fact I need to additionally check for self.traitCollection.userInterfaceStyle != previousTraitCollection?.userInterfaceStyle to determine whether the dark / light appearance has actually changed.
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