iOS重新设置window的rootViewController

有xib文件时的写法

<code>

• (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
  self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
  [_window release];
  // Override point for customization after application launch.
  RootViewController *rootVC = [[RootViewController alloc] initWithNibName:@"RootViewController" bundle:nil];
  //默认从包里边来找,所以是nil
  self.window.rootViewController = rootVC;
  [rootVC release];
  self.window.backgroundColor = [UIColor redColor];
  [self.window makeKeyAndVisible];
  return YES;
  }
  </code>