iOS 13+的答案(找到键窗口的代码来源):

guard let window = UIApplication.shared.windows.first(where: { $0.isKeyWindow }) else {
    return
}

let windowWidth = window.frame.width
let windowHeight = window.frame.height

这是非常非常容易得到你的设备大小，以及考虑方向:

// grab the window frame and adjust it for orientation
UIView *rootView = [[[UIApplication sharedApplication] keyWindow] 
                                   rootViewController].view;
CGRect originalFrame = [[UIScreen mainScreen] bounds];
CGRect adjustedFrame = [rootView convertRect:originalFrame fromView:nil];

注意，[UIScreen mainScreen]包含状态栏，如果你想检索你的应用程序的框架(不包括状态栏)，你应该使用

+ (CGFloat) window_height   {
    return [UIScreen mainScreen].applicationFrame.size.height;
}

+ (CGFloat) window_width   {
    return [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
}

你可以把这些宏放在你的pch文件中，并使用"SCREEN_WIDTH"在项目的任何地方使用

#define SCREEN_WIDTH                ((([UIApplication sharedApplication].statusBarOrientation == UIInterfaceOrientationPortrait) || ([UIApplication sharedApplication].statusBarOrientation == UIInterfaceOrientationPortraitUpsideDown)) ? [[UIScreen mainScreen] bounds].size.width : [[UIScreen mainScreen] bounds].size.height)

和“SCREEN_HEIGHT”

#define SCREEN_HEIGHT               ((([UIApplication sharedApplication].statusBarOrientation == UIInterfaceOrientationPortrait) || ([UIApplication sharedApplication].statusBarOrientation ==   UIInterfaceOrientationPortraitUpsideDown)) ? [[UIScreen mainScreen] bounds].size.height : [[UIScreen mainScreen] bounds].size.width)

使用示例:

CGSize calCulateSizze ;
calCulateSizze.width = SCREEN_WIDTH/2-8;
calCulateSizze.height = SCREEN_WIDTH/2-8;

iOS 13+的答案(找到键窗口的代码来源):

guard let window = UIApplication.shared.windows.first(where: { $0.isKeyWindow }) else {
    return
}

let windowWidth = window.frame.width
let windowHeight = window.frame.height