师傅发我一堆view的创建函数，目的让我知道view的创建过程。

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
    if (self) {
        // Custom initialization
    }
    return self;
}
- (void)viewWillAppear:(BOOL)animated
{

}
- (void)viewDidAppear:(BOOL)animated
{

}
- (void)loadView
{

}
- (void)layoutSublayersOfLayer:(CALayer *)layer
{

}
- (void)viewWillLayoutSubviews
{

}
 - (void)viewDidLoad
{

}

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    self.window = [[UIWindow alloc]initWithFrame:[[UIScreen mainScreen] bounds]];

 
    self.window.rootViewController = [[MyViewController alloc]init];
    
    [self.window makeKeyAndVisible];
    // Override point for customization after application launch.
    return YES;
}

然后运行   。。。。。。凉了。。。出现错误了；

启动起来黑屏，然后是报这样一个错误Application windows are expected to have a root view controller at the end of application launch

2014-08-13 15:16:45.924 任务1副本[2629:60b] -[YouVC loadView]
2014-08-13 15:16:45.925 任务1副本[2629:60b] -[YouVC viewDidLoad]
2014-08-13 15:16:45.925 任务1副本[2629:60b] -[YouVC loadView]
2014-08-13 15:16:45.926 任务1副本[2629:60b] -[YouVC viewDidLoad]
2014-08-13 15:16:45.927 任务1副本[2629:60b] -[YouVC loadView]
2014-08-13 15:16:45.927 任务1副本[2629:60b] -[YouVC viewDidLoad]
2014-08-13 15:16:45.928 任务1副本[2629:60b] -[YouVC loadView]
2014-08-13 15:16:45.928 任务1副本[2629:60b] -[YouVC viewDidLoad]
2014-08-13 15:16:45.929 任务1副本[2629:60b] Application windows are expected to have a root view controller at the end of application launch

无解 ，网上搜得所有方案都不对。我把焦点放在了 self.window.rootviewcontroller = ....这句话上了；

我开始想它出错的原因，为什么这些方法调用了好几遍，单步调试发现这些函数不止是在初始化的init时候调用。

我又新建了一个viewcontroller就加了一个背景色，结果能运行，我又试着将师傅给的代码贴上去，结果又出现错误了。

我就开始挨个试是什么出现了问题，最后让我找到了原因出在-（void）loadview这个函数上面；

我又开始查询这个函数，最后从M了个J老师这获得了答案：

原来在每次调用view的时候，如果view为空，则会调用这个函数；他的作用就是来创建一个view，首先加载xib 如果没有xib 则自动创建一个大小320*480 的空白view；

在程序的

-（void）loadview 中加入了[super loadview];后程序能够运行了；

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
    if (self) {
        // Custom initialization
    }
    return self;
}
-(id)init
{
    if(self = [super init])
    {
        self.view.frame=[[UIScreen mainScreen]bounds];
        self.view.backgroundColor = [UIColor orangeColor];
    }
    return self;
}
- (void)loadView
{
   // [super loadView];
    NSLog(@"%s",__FUNCTION__);

}

- (void)viewDidLoad
{
    [super viewDidLoad];
    NSLog(@"%s",__FUNCTION__);
    // Do any additional setup after loading the view from its nib.
}
- (void)viewWillAppear:(BOOL)animated
{
    NSLog(@"%s",__FUNCTION__);
}
- (void)viewDidAppear:(BOOL)animated
{
    NSLog(@"%s",__FUNCTION__);
}

- (void)layoutSublayersOfLayer:(CALayer *)layer
{
    NSLog(@"%s",__FUNCTION__);
    
}
- (void)viewWillLayoutSubviews
{
    NSLog(@"%s",__FUNCTION__);
}

运行结果：

2014-08-13 15:35:54.783 任务1副本[2660:60b] -[YouVC loadView]
2014-08-13 15:35:54.783 任务1副本[2660:60b] -[YouVC viewDidLoad]
2014-08-13 15:35:54.784 任务1副本[2660:60b] -[YouVC viewWillAppear:]
2014-08-13 15:35:54.785 任务1副本[2660:60b] -[YouVC viewWillLayoutSubviews]
2014-08-13 15:35:54.835 任务1副本[2660:60b] -[YouVC viewDidAppear:]

M了个J老师的博客 http://www.cnblogs.com/mjios/archive/2013/02/26/2933667.html里面详细讲述了这几个函数；

ios view的创建过程,布布扣,bubuko.com

ios view的创建过程