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  • 程序的入口及AppDelegate窗体显示原理

    AppDelegate.m

    - (void)dealloc
    {
        [_window release];
        [super dealloc];
    }
    
    - (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
    {
        
        self.window = [[UIWindow alloc] initWithFrame:CGRectMake(0, 0, 320, 480)];
        self.window.backgroundColor = [UIColor redColor];
        
        /*
         makeKeyAndVisible的作用:
         1.让window在屏幕上直接显示,这是window的属性。view没有这个属性,假设室view,须要加入到其它的视图上显示
         2.将当前窗体设置为主窗体
         */
        [_window makeKeyAndVisible];
        
        _window.windowLevel = UIWindowLevelStatusBar;
        
        UIWindow *w2 = [[UIWindow alloc] initWithFrame:CGRectMake(0, 0, 90, 90)];
        w2.backgroundColor = [UIColor greenColor];
    //    [w2 makeKeyAndVisible];   不能这么写
        
        //hidden的作用:在主窗体上显示w2,可是w2不是主窗体
        w2.hidden = NO;
        
        /*
         设置window的优先级:UIWindowLevelNormal < UIWindowLevelStatusBar < UIWindowLevelAlert;
         默认是:UIWindowLevelNormal
         */
        w2.windowLevel = UIWindowLevelAlert;
        
        //拿到当前程序的主window
        UIWindow *w3 = application.keyWindow;
        NSLog(@"self.window:%@",self.window);
        NSLog(@"w3:%@",w3);
        
        
        return YES;
    }


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  • 原文地址:https://www.cnblogs.com/gccbuaa/p/7281912.html
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