创建一个新工程
删除MainStoryBord LauchScreen.storyboard ViewController.m,ViewController.h
Targets—General将Launch Screan File设置为空
Targets—General—Deployment info 将MainIterface 设置为空
Assets.xcassets中添加一个LauchImage
将Launch Images Source 设置为Assets.xcassets中的LauchImage
代码：
self.window = [[UIWindow alloc]initWithFrame:[[UIScreen mainScreen] bounds]]
self.window.rootViewController = xxx;
self.window.backgroundColor = [UIColor whiteColor];
[self.window makeKeyAndVisible];
