创建UINavigationController

设置UIWindow的根视图为导航控制器  

#import "CYYAppDelegate.h"
#import "CYYViewController.h"

@implementation CYYAppDelegate

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
    self.window.backgroundColor = [UIColor whiteColor];
   
    // 1. 实例化导航控制器
    CYYViewController *one = [[CYYViewController alloc] init];
   
    UINavigationController *nav = [[UINavigationController alloc] initWithRootViewController:one];
    nav.view.backgroundColor = [UIColor redColor];

   
    self.window.rootViewController = nav;
   
    [self.window makeKeyAndVisible];
    return YES;
}