pragma mark ----- 获取window的方法 -----------
//第一种: 获取当前view的window
self.view.window.rootViewController = [[UIStoryboard storyboardWithName:@"Main" bundle:nil] instantiateInitialViewController];
//第二种: 获取当前应用的window
[UIApplication sharedApplication].keyWindow.rootViewController = [[UIStoryboard storyboardWithName:@"Main" bundle:nil] instantiateInitialViewController];