视图控制器及生命周期

import "AppDelegate.h"

import "RootViewController.h"

@interface AppDelegate ()

@end

@implementation AppDelegate

• (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];

  // 创建视图控制器对象
  RootViewController rootVC = [[RootViewController alloc]init];
  // 将创建好的视图控制器设置为window的根视图控制器
  [self.window setRootViewController:rootVC];
  /*

  • 模拟window类中，setRootViewController
    -(viod) setRootViewController:(UIViewContorller) rootVC{
    if(_rootViewController != rootVC ){
    [_rootViewController release];
    _rootViewController = [rootVC retain];
    }
    [self addSubView:_rootViewController.view];
    }
    */
    return YES;
    }

import "RootViewController.h"

@interface RootViewController ()
@end
@implementation RootViewController

// 创建视图控制器的时候，系统会帮我们创建一个和屏幕一样宽高的视图（view）作为视图控制器的属性
// 加载视图控制器自带的视图 当使用到该视图控制器自带的view时（调用view属性的get方法的时候），才会调用loadview方法创建该view

// 视图加载
-(void)loadView{
NSLog(@"%s",func);
// [super loadView];// 如果我们使用自定义的视图，就不要调用[super loadview]
// 自定义视图 (自定义的视图frame的尺寸创建时已经给定根屏幕一样的宽高，所以无法修改)
UIView *customView = [[UIView alloc]initWithFrame:CGRectMake(0, 0, CGRectGetWidth([UIScreen mainScreen].bounds), CGRectGetHeight([UIScreen mainScreen].bounds))];
customView.backgroundColor = [UIColor redColor];
// 将自定义的视图赋给当前视图控制器的view
self.view = customView;
}

// 创建label的方法
-(UILabel *)creatLabel{
UILabel *label = [[UILabel alloc]initWithFrame:CGRectZero];
label.text = @"title";
label.tag = 1000;
return label;
}

// 视图加载完毕

• (void)viewDidLoad {
  NSLog(@"%s",func);
  [super viewDidLoad];
  // self.view.backgroundColor = [UIColor yellowColor];

  // Do any additional setup after loading the view.
  }

// 视图即将出现
-(void)viewWillAppear:(BOOL)animated{
NSLog(@"%s",func);
[super viewWillAppear:animated];
}

// 视图已经出现
-(void)viewDidAppear:(BOOL)animated{
NSLog(@"%s",func);
[super viewDidAppear:animated];
}

// 视图即将消失
-(void)viewWillDisappear:(BOOL)animated{
NSLog(@"%s",func);
[super viewWillDisappear:animated];
}

// 视图已经消失
-(void)viewDidDisappear:(BOOL)animated{
NSLog(@"%s",func);
[super viewDidDisappear:animated];
}

// 视图被释放掉
-(void)dealloc{
// ARC下dealloc方法可以被重写，但是不能在内部使用[super dealloc]
// [super dealloc];
}

-(void)didReceiveMemoryWarning {
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}