版本的判断

// =
#define STDEVICE_Same(v)    [[UIDevice currentDevice].systemVersion compare:v options:NSNumericSearch] == NSOrderedSame
// <
#define STDEVICE_Less(v)    [[UIDevice currentDevice].systemVersion compare:v options:NSNumericSearch] == NSOrderedAscending
// >
#define STDEVICE_Than(v)    [[UIDevice currentDevice].systemVersion compare:v options:NSNumericSearch] == NSOrderedDescending
// >=
#define STDEVICE_Than_Same(v)    [[UIDevice currentDevice].systemVersion compare:v options:NSNumericSearch] != NSOrderedAscending
// <=
#define STDEVICE_Less_Same(v)    [[UIDevice currentDevice].systemVersion compare:v options:NSNumericSearch] != NSOrderedDescending

ios 8之后屏幕的宽高发生了变化

iOS7

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)

ios8

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)

因此

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！iOS8的statusbar还会在横屏默认隐藏

新增的api iOS8 nativebounds nativeScale

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

结论iOS 8的nativebounds固定不变

写个分类

@implementation UIScreen (Additions)

+ (float)screenWidth{
    
    

    
    
    if (UIInterfaceOrientationIsLandscape([UIApplication sharedApplication].statusBarOrientation)) {
        if ([[UIDevice currentDevice].systemVersion floatValue]>=8.0) {
            return [UIScreen mainScreen].nativeBounds.size.height/[UIScreen mainScreen].nativeScale;
        } else {
            return [UIScreen mainScreen].bounds.size.height;
        }
    } else {
        if ([[UIDevice currentDevice].systemVersion floatValue]>=8.0) {
            return [UIScreen mainScreen].nativeBounds.size.width/[UIScreen mainScreen].nativeScale;
        } else {
            return [UIScreen mainScreen].bounds.size.width;
        }
    }
}

+ (float)screenHeight{
    if (UIInterfaceOrientationIsLandscape([UIApplication sharedApplication].statusBarOrientation)) {
        if ([[UIDevice currentDevice].systemVersion floatValue]>=8.0) {
            if ([UIApplication sharedApplication].statusBarFrame.size.width>20) {
                return [UIScreen mainScreen].nativeBounds.size.width/[UIScreen mainScreen].nativeScale-20;
            }
            return [UIScreen mainScreen].nativeBounds.size.width/[UIScreen mainScreen].nativeScale;
        } else {
            if ([UIApplication sharedApplication].statusBarFrame.size.width>20) {
                return [UIScreen mainScreen].bounds.size.width-20;
            }
            return [UIScreen mainScreen].bounds.size.width;
        }
    } else {
        if ([[UIDevice currentDevice].systemVersion floatValue]>=8.0) {
            if ([UIApplication sharedApplication].statusBarFrame.size.height>20) {
                return [UIScreen mainScreen].nativeBounds.size.height/[UIScreen mainScreen].nativeScale-20;
            }
            return [UIScreen mainScreen].nativeBounds.size.height/[UIScreen mainScreen].nativeScale;
        } else {
            if ([UIApplication sharedApplication].statusBarFrame.size.height>20) {
                return [UIScreen mainScreen].bounds.size.height-20;
            }
            return [UIScreen mainScreen].bounds.size.height;
        }
    }
}

+ (BOOL)isRetina{
    if ([[UIDevice currentDevice].systemVersion floatValue]>=8.0) {
        return [UIScreen mainScreen].nativeScale>=2;
    } else {
        return [UIScreen mainScreen].scale>=2;
    }
}

+ (float)scale{
    if ([[UIDevice currentDevice].systemVersion floatValue]>=8.0) {
        return [UIScreen mainScreen].nativeScale;
    } else {
        return [UIScreen mainScreen].scale;
    }
}