1     NS_CLASS_AVAILABLE_IOS(2_0)  @interface UIWindow : UIView
2     @available(iOS 2.0, *)       public class UIWindow : UIView

 1     // 声明窗口视图
 2     @property (strong, nonatomic) UIWindow *window; 
 3 
 4     - (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
 5 
 6         // 实例化窗口视图，window 的大小和当前手机屏幕一样大
 7         self.window = [[UIWindow alloc] initWithFrame: [UIScreen mainScreen].bounds];   
 8 
 9         // 设置 window 的背景颜色
10         self.window.backgroundColor = [UIColor whiteColor];  
11 
12         // 将窗口显示到屏幕上
13         [self.window makeKeyAndVisible];
14 
15         return YES;
16     }

 1     // 声明窗口视图
 2     var window: UIWindow?
 3 
 4     func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool {
 5 
 6         // 实例化窗口视图，window 的大小和当前手机屏幕一样大
 7         self.window = UIWindow(frame: UIScreen.mainScreen().bounds)
 8 
 9         // 设置 window 的背景颜色
10         self.window?.backgroundColor = UIColor.whiteColor()
11 
12         // 将窗口显示到屏幕上 
13         self.window?.makeKeyAndVisible()
14 
15         return true
16     }

1     // 当前屏幕的宽度
2     CGFloat width =  [UIScreen mainScreen].bounds.size.width;
3 
4     // 当前屏幕的高度      
5     CGFloat height = [UIScreen mainScreen].bounds.size.height;

1     // 当前屏幕的宽度
2     let width:CGFloat = UIScreen.mainScreen().bounds.size.width
3 
4     // 当前屏幕的高度
5     let height:CGFloat = UIScreen.mainScreen().bounds.size.height