let orientation: UIInterfaceOrientation = UIApplication.sharedApplication().statusBarOrientation

        println("Currently landscape: " + ((orientation == UIInterfaceOrientation.LandscapeLeft||orientation == UIInterfaceOrientation.LandscapeRight) ?"YES":"NO"))

        println("UIScreen.mainScreen().bounds: \(UIScreen.mainScreen().bounds)")

        println("UIScreen.mainScreen().applicationFrame: \(UIScreen.mainScreen().applicationFrame)")

在ios7中输出：

Currently landscape: NO

UIScreen.mainScreen().bounds: (0.0,0.0,320.0,568.0)

UIScreen.mainScreen().applicationFrame: (0.0,20.0,320.0,548.0)

Currently landscape: YES

UIScreen.mainScreen().bounds: (0.0,0.0,320.0,568.0)

UIScreen.mainScreen().applicationFrame: (20.0,0.0,300.0,568.0)

在ios8中输出：

Currently landscape: NO

UIScreen.mainScreen().bounds: (0.0,0.0,320.0,568.0)

UIScreen.mainScreen().applicationFrame: (0.0,20.0,320.0,548.0)

Currently landscape: YES

UIScreen.mainScreen().bounds: (0.0,0.0,568.0,320.0)

UIScreen.mainScreen().applicationFrame: (0.0,0.0,568.0,320.0)

结论：

1、在ios7中UIScreen.mainScreen().bounds是固定不变的值，在ios8中他的值是随横竖屏改变的！

为了在ios8中得到原来的效果可以：

+ (CGSize)screenSize {

    CGSize screenSize = [UIScreen mainScreen].bounds.size;

    return CGSizeMake(MIN(screenSize.width, screenSize.height), MAX(screenSize.width, screenSize.height));

}

2、

在ios8中增加了2个属性：

nativeBounds :  屏幕像素，不随横竖平改变的！

nativeScale   ：1(non retina)/2(retina)/3(retina hd)

https://developer.apple.com/library/ios/documentation/UIKit/Reference/UIScreen_Class/index.html#//apple_ref/occ/instp/UIScreen/nativeBounds

ios8输出：

Currently landscape: YES

UIScreen.mainScreen().bounds: (0.0,0.0,568.0,320.0)

UIScreen.mainScreen().applicationFrame: (0.0,20.0,568.0,300.0)

UIScreen.mainScreen().nativeBounds: (0.0,0.0,640.0,1136.0)

UIScreen.mainScreen().nativeScale: 2.0

Currently landscape: NO

UIScreen.mainScreen().bounds: (0.0,0.0,320.0,568.0)

UIScreen.mainScreen().applicationFrame: (0.0,20.0,320.0,548.0)

UIScreen.mainScreen().nativeBounds: (0.0,0.0,640.0,1136.0)

UIScreen.mainScreen().nativeScale: 2.0

3、从UIScreen.mainScreen().applicationFrame输出值看出，ios8默认横屏statusbar是隐藏掉了。你可以根据plist中

View controller-based status bar appearance的值的不同来用

UIApplication.sharedApplication().setStatusBarHidden(false, withAnimation: UIStatusBarAnimation.None)

或

  override func prefersStatusBarHidden() -> Bool {

        return false

    }

显示横屏statusbar