一嫩实、UIApplication
1.打開網(wǎng)頁

    // URL：資源路徑
    // URL：協(xié)議頭://域名+路徑  http,https,file,tel
    // 協(xié)議頭:
    // 打開網(wǎng)頁 @"http://www.baidu.com"
    
    NSURL *url = [NSURL URLWithString:@"http://www.baidu.com"];
    
    [[UIApplication sharedApplication] openURL:url]; //跳到Safari打開網(wǎng)頁

2.隱藏狀態(tài)欄

    // 獲取UIApplication
    UIApplication *app = [UIApplication sharedApplication];
   
    // 隱藏狀態(tài)欄
    //    [app setStatusBarHidden:YES];
    
    [app setStatusBarHidden:YES withAnimation:UIStatusBarAnimationSlide];
// 在iOS7以后恨狈，狀態(tài)欄默認由控制器決定
// 隱藏狀態(tài)欄
//- (BOOL)prefersStatusBarHidden
//{
//    return YES;
//}


//- (UIStatusBarStyle)preferredStatusBarStyle
//{
//    return UIStatusBarStyleLightContent;
//}

3.設(shè)置提醒數(shù)字

// 1.整個app中只有一個UIApplication
    
    //    UIApplication *app = [[UIApplication alloc] init];
    
    UIApplication *app = [UIApplication sharedApplication];
    
    // 2.UIApplication一般用來做一些應(yīng)用級別的操作（app的提醒框帚戳，聯(lián)網(wǎng)狀態(tài)峻仇，打電話樱蛤，打開網(wǎng)頁壮莹，控制狀態(tài)欄）
    //    UIApplication *app1 = [UIApplication sharedApplication];
    
    // 設(shè)置appIcon提醒數(shù)字，必須注冊用戶通知
    app.applicationIconBadgeNumber = 10;
    // 創(chuàng)建用戶通知
    UIUserNotificationSettings *settings = [UIUserNotificationSettings settingsForTypes:UIUserNotificationTypeBadge categories:nil];
    // 注冊用戶的通知
    [app registerUserNotificationSettings:settings];
    
    // 設(shè)置聯(lián)網(wǎng)狀態(tài)
    app.networkActivityIndicatorVisible = YES;

二荣德、UIWindow
1.AppDelegate.h中的window屬性

// 程序啟動完成的時候
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
    // Override point for customization after application launch.
    
    // 1.創(chuàng)建窗口,注意窗口必須要有尺寸隧土，尺寸跟屏幕一樣大的尺寸,窗口不要被釋放
    self.window = [[UIWindow alloc] initWithFrame:[UIScreen mainScreen].bounds];
    self.window.backgroundColor = [UIColor redColor];
    
    // 2.創(chuàng)建窗口的根控制器
    UIViewController *vc = [[UIViewController alloc] init];
    vc.view.backgroundColor = [UIColor yellowColor];
    
    [vc.view addSubview:[UIButton buttonWithType:UIButtonTypeContactAdd]];
    
    // 如果設(shè)置窗口的根控制器，默認就會把控制器的view添加到窗口上
    // 設(shè)置窗口的根控制器命爬，默認就有旋轉(zhuǎn)功能
    self.window.rootViewController = vc;
    
//    [self.window addSubview:vc.view];
    
    // 3.顯示窗口
    [self.window makeKeyAndVisible];
    
    return YES;
}

2.窗口是有層級關(guān)系
UIWindowLevelNormal < UIWindowLevelStatusBar < UIWindowLevelAlert

// 設(shè)置窗口的層級關(guān)系
    self.window1.windowLevel = UIWindowLevelStatusBar;