我原先是这么做的，通常也是这么做
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
// Override point for customization after application launch.
ViewController *firstVC = [[ViewController alloc] init];
UINavigationController *naviController = [[UINavigationController alloc] initWithRootViewController:firstVC];
self.window.rootViewController = naviController;
self.window.backgroundColor = [UIColor whiteColor];
[self.window makeKeyAndVisible];
return YES;
}
然而运行后，UINavigationController的确作为windows的根视图显示了，但是firstVC里的控件却没有显示，一片空白
事实证明不能这样直接alloc firstVC，而是要从storyboard中加载，我改成如下就行了：
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
// Override point for customization after application launch.
UIStoryboard *storyBoard = [UIStoryboard storyboardWithName:@"Main_" bundle:nil];
ViewController *firstVC = [storyBoard instantiateViewControllerWithIdentifier:@"MainView"];
UINavigationController *naviController = [[UINavigationController alloc] initWithRootViewController:firstVC];
self.window.rootViewController = naviController;
self.window.backgroundColor = [UIColor whiteColor];
[self.window makeKeyAndVisible];
return YES;
}
我查看过很多代码例子都是像前者一样直接alloc加载就可以，但是我这里却不行，一定要这样从storyboard中加载，我哪里没注意到望大神告知