在横向启动我的 Swift 应用程序时设备屏幕宽度错误

Question

I use this code to get the screen width and height

public var width: CGFloat {
    return UIScreen.main.bounds.width
}

public var height: CGFloat {
    return UIScreen.main.bounds.height
}

After a rotation the code is working fine but if I start the app in Landscape mode, the returned height in viewDidLoad is wrong and is 812.0, which is the width. If I rotate to portrait and than back to landscape, than the value is 375.0 which is right.

Answer 1

According to this answer , you should run your code in viewWillAppear and/or viewDidLayoutSubviews . When viewDidLoad is called, that view controller's view is guaranteed to be loaded into memory, but it is not yet rendered. viewWillAppear is called when a view is about to be added to an on-screen view hierarchy, as detailed in the Apple developer documentation . At this point, the view controller should be able to access the orientation that the device is in, since its content views will most likely be rendered when viewWillAppear is called. If your code is still returning the wrong values, you may need to move it into viewDidLayoutSubviews , which is called whenever the bounds of the current view will change.

Edit: it looks like you will need to flip the width and height values based on the orientation and their relationship to one another, as stated in this answer , although that is in Objective-C. In Swift:

public var width: CGFloat {
    //If in landscape mode
    if (UIApplication.shared.statusBarOrientation.isLandscape) {
        //If in landscape and the width is less than the height (wrong),
        //return the height instead of the width 
        if (UIScreen.main.bounds.width < UIScreen.main.bounds.height) {
            return UIScreen.main.bounds.height
        }
    }
    //Else just return the width
    return UIScreen.main.bounds.width
}

public var height: CGFloat {
    //If in landscape mode
    if (UIApplication.shared.statusBarOrientation.isLandscape) {
        //If in landscape and the height is greater than the width (wrong),
        //return the width instead of the height 
        if (UIScreen.main.bounds.height > UIScreen.main.bounds.width) {
            return UIScreen.main.bounds.width
        }
    }
    //Else just return the height
    return UIScreen.main.bounds.height
}