我意识到这是一篇旧文章，但有时我发现#定义这样的常量很有用，这样我就不必担心它:

#define DEVICE_SIZE [[[[UIApplication sharedApplication] keyWindow] rootViewController].view convertRect:[[UIScreen mainScreen] bounds] fromView:nil].size

无论设备朝向如何，上述常量都应返回正确的大小。然后获取尺寸就像这样简单:

lCurrentWidth = DEVICE_SIZE.width;
lCurrentHeight = DEVICE_SIZE.height;

利用这些struct来了解Swift中当前设备的有用信息。

struct ScreenSize { // Answer to OP's question
    
    static let SCREEN_WIDTH         = UIScreen.main.bounds.size.width
    static let SCREEN_HEIGHT        = UIScreen.main.bounds.size.height
    static let SCREEN_MAX_LENGTH    = max(ScreenSize.SCREEN_WIDTH, ScreenSize.SCREEN_HEIGHT)
    static let SCREEN_MIN_LENGTH    = min(ScreenSize.SCREEN_WIDTH, ScreenSize.SCREEN_HEIGHT)
    
}

struct DeviceType { //Use this to check what is the device kind you're working with
    
    static let IS_IPHONE_4_OR_LESS  = UIDevice.current.userInterfaceIdiom == .phone && ScreenSize.SCREEN_MAX_LENGTH < 568.0
    static let IS_IPHONE_SE         = UIDevice.current.userInterfaceIdiom == .phone && ScreenSize.SCREEN_MAX_LENGTH == 568.0
    static let IS_IPHONE_7          = UIDevice.current.userInterfaceIdiom == .phone && ScreenSize.SCREEN_MAX_LENGTH == 667.0
    static let IS_IPHONE_7PLUS      = UIDevice.current.userInterfaceIdiom == .phone && ScreenSize.SCREEN_MAX_LENGTH == 736.0
    static let IS_IPHONE_X          = UIDevice.current.userInterfaceIdiom == .phone && ScreenSize.SCREEN_MAX_LENGTH == 812.0
    static let IS_IPAD              = UIDevice.current.userInterfaceIdiom == .pad && ScreenSize.SCREEN_MAX_LENGTH == 1024.0
    
}


struct iOSVersion { //Get current device's iOS version
    
    static let SYS_VERSION_FLOAT  = (UIDevice.current.systemVersion as NSString).floatValue
    static let iOS7               = (iOSVersion.SYS_VERSION_FLOAT >= 7.0 && iOSVersion.SYS_VERSION_FLOAT < 8.0)
    static let iOS8               = (iOSVersion.SYS_VERSION_FLOAT >= 8.0 && iOSVersion.SYS_VERSION_FLOAT < 9.0)
    static let iOS9               = (iOSVersion.SYS_VERSION_FLOAT >= 9.0 && iOSVersion.SYS_VERSION_FLOAT < 10.0)
    static let iOS10              = (iOSVersion.SYS_VERSION_FLOAT >= 10.0 && iOSVersion.SYS_VERSION_FLOAT < 11.0)
    static let iOS11              = (iOSVersion.SYS_VERSION_FLOAT >= 11.0 && iOSVersion.SYS_VERSION_FLOAT < 12.0)
    static let iOS12              = (iOSVersion.SYS_VERSION_FLOAT >= 12.0 && iOSVersion.SYS_VERSION_FLOAT < 13.0)
    static let iOS13              = (iOSVersion.SYS_VERSION_FLOAT >= 13.0 && iOSVersion.SYS_VERSION_FLOAT < 14.0)
    static let iOS14              = (iOSVersion.SYS_VERSION_FLOAT >= 14.0 && iOSVersion.SYS_VERSION_FLOAT < 15.0)
    static let iOS15              = (iOSVersion.SYS_VERSION_FLOAT >= 15.0 && iOSVersion.SYS_VERSION_FLOAT < 16.0)
    static let iOS16              = (iOSVersion.SYS_VERSION_FLOAT >= 16.0 && iOSVersion.SYS_VERSION_FLOAT < 17.0)
    
}

NSLog(@"%.0f", [[UIScreen mainScreen] bounds].size.width);
NSLog(@"%.0f", [[UIScreen mainScreen] bounds].size.height);

斯威夫特3.0

的宽度

UIScreen.main.bounds.size.width

身高

UIScreen.main.bounds.size.height

我们还必须考虑设备的朝向:

CGFloat screenHeight;
// it is important to do this after presentModalViewController:animated:
if ([[UIApplication sharedApplication] statusBarOrientation] == UIDeviceOrientationPortrait || [[UIApplication sharedApplication] statusBarOrientation] == UIDeviceOrientationPortraitUpsideDown){
    screenHeight = [UIScreen mainScreen].applicationFrame.size.height;
}
else{
    screenHeight = [UIScreen mainScreen].applicationFrame.size.width;
}

这里我已经更新了swift 3

applicationFrame已从iOS 9弃用

在swift 3中，他们已经删除了()，他们已经改变了一些命名惯例，你可以参考这里的链接

func windowHeight() -> CGFloat {
    return UIScreen.main.bounds.size.height
}

func windowWidth() -> CGFloat {
    return UIScreen.main.bounds.size.width
}