ios view的创建过程

来源：互联网发布：windows改变图标编辑：程序博客网时间：2024/04/30 01:57

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{}

拿到这函数我也没多想就创建了一个single View application 然后创建一个viewcontroller 就将师傅的函数复制进去，然后在AppDelegeteD.m文件中写

- (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:]

这个就是创建view的时候，相关view创建函数的运行次序：

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；

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