XCode空白工程，手工添加Storyboard步骤

XCode新建空白工程后，手工增加Storyboard并添加ViewController后，只显示空白，不显示ViewController：
调试时会提示：

Application windows are expected to have a root view controller at the end of application launch

这时，需要手工修改一处代码和一处配置：
1、AppDelegate源码文件

//修改前
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
    // Override point for customization after application launch.
    self.window.backgroundColor = [UIColor whiteColor];
    [self.window makeKeyAndVisible];

    return YES;
}

//修改后
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    return YES;
}

2、指定启动的Storyboard
在Project-》Targets-》Summary中修改Main Storyboard属性为新添加的Storyboard名称（不带后缀）。
或者
修改XXX-Info.plist文件，添加属性

<key>UIMainStoryboardFile</key>
<string>Storyboard名称（不带后缀）</string>

然后就OK啦。