在定向更改后查询UIScreen.main.bounds.height
时,我得到了一些奇怪的结果。也许这不是正确的方法。
我有一个观察者,听取NSNotification.Name.UIDeviceOrientationDidChange
事件:
NotificationCenter.default.addObserver(self, selector: #selector(self.orientationChange), name: NSNotification.Name.UIDeviceOrientationDidChange, object: nil)
这会调用一个将约束设置为新屏幕高度的75%的函数。这适用于iPhone,但iPad返回错误的屏幕高度。
如果iPad处于横向,UIScreen.main.bounds.height
将返回一个等于纵向高度的值,反之亦然。
func orientationChange() {
// This will print the correct value on iPhone and iPad.
if UIDevice.current.orientation.isLandscape {
print("Landscape")
} else {
print("Portrait")
}
let screenSize = UIScreen.main.bounds
let screenHeight = screenSize.height
self.searchViewHeightConstraint.constant = screenHeight * 0.75
// Correct value on iPhone. Incorrect on iPad.
print("screenHeight: '\(screenHeight)'")
UIView.animate(withDuration: 0.6, delay: 0, usingSpringWithDamping: 0.8, initialSpringVelocity: 0, options: .curveEaseOut, animations: {
self.searchView.superview?.layoutIfNeeded()
}, completion: nil)
}
我也遇到了监测方向变化的viewWilltransition
方法,但这与上述方法完全相反。即。 iPad上的高度是正确的但在iPhone上不正确:
override func viewWillTransition(to size: CGSize, with coordinator: UIViewControllerTransitionCoordinator) {
let screenSize = UIScreen.main.bounds
let screenHeight = screenSize.height
self.searchViewHeightConstraint.constant = screenHeight * 0.75
// Correct value on iPad. Incorrect on iPhone.
print("screenHeight: '\(screenHeight)'")
}
iPhone和iPad之间这种不一致行为的原因是什么,并且正在使用NotificationCenter
监控方向变化的正确方法?
你应该使用的是viewWillTransition(to size: CGSize, with coordinator: UIViewControllerTransitionCoordinator)
。这将为您提供尺寸,并且比使用通知更可靠。
此外,如果你想做动画,在UIViewControllerTransitionCoordinator内你可以利用方法animate(alongsideTransition animation: ((UIViewControllerTransitionCoordinatorContext) -> Swift.Void)?, completion: ((UIViewControllerTransitionCoordinatorContext) -> Swift.Void)? = nil) -> Bool
你需要使用:
dispatch_async(dispatch_get_main_queue()) {
println("h:\(view.bounds.size.height)")
println("w:\(view.frame.size.width)")
}
//你需要在dispatch_async下编写代码
旋转完成后(在主队列中)将执行此代码,并且新的大小可用。
对于iPad和iPhone,这适用于Swift 2.3。
override func viewWillTransitionToSize(size: CGSize, withTransitionCoordinator coordinator: UIViewControllerTransitionCoordinator) {
print(size.height)
if UIDevice.currentDevice().orientation.isLandscape {
print("Landscape")
print(size.height)
}
else {
print("Portrait")
print(size.height)
}
}