IOS 代码创建控件，并有处理事件详解手机开发

    @interface AppDelegate()   
       
    @property UILabel* show;   
    @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];   
           
        //创建一个UIViewController 对象   
        UIViewController* controller = [[UIViewController alloc] init];   
        //让该程序的窗口加载并显示 viewController 视图控制器关联的用户界面   
        self.window.rootViewController = controller;   
        //创建一个UIView 对象   
        UIView* rootView = [[UIView alloc] initWithFrame:[[UIScreen mainScreen] bounds]];   
        //设置 controller 显示 rootView 控件   
        controller.view = rootView;   
        //创建一个圆角按钮   
        UIButton* button = [UIButton buttonWithType:UIButtonTypeRoundedRect];   
        //设置按钮的大小   
        button.frame = CGRectMake(120, 100, 80, 40);   
        //为按钮设置文本   
        [button setTitle:@"确定" forState:UIControlStateNormal];   
        //将按钮添加到 rootView 控件中   
        [rootView addSubview:button];   
        //创建一个 UILabel 对象   
        self.show = [[UILabel alloc] initWithFrame:CGRectMake(60, 40, 180, 30)];   
    //    UILabel* show = [[UILabel alloc] initWithFrame:CGRectMake(60, 40, 180, 30)];   
        //将UILabel 添加到 rootView 控件中   
        [rootView addSubview: self.show];   
        //设置 UILabel 默认显示的文本   
        self.show.text = @"初始文本";   
        self.show.backgroundColor = [UIColor grayColor];   
        //为圆角按钮的触碰事件绑定事件处理方法   
        [button addTarget:self action:@selector(clickHandler:) forControlEvents:UIControlEventTouchUpInside];   
           
        //将该 UIWindow 对象设为主窗口并显示出来   
        [self.window makeKeyAndVisible];   
        return YES;   
    }  

    - (void)clickHandler:(id)sender {   
        self.show.text = @"开始学习 IOS 吧！";   
    }