IOS UIApplication使用

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.

//    UIApplication *app = [UIApplication sharedApplication];
//    UIApplication *app1 = [UIApplication sharedApplication];
////    UIApplication *app2 = [[UIApplication alloc] init];
//    NSLog(@"%p - %p ", app, app1);

    UIButton *btn = [[UIButton alloc] initWithFrame:CGRectMake(, , , )];
    [btn setTitle:@"点我啊" forState:UIControlStateNormal];
    [btn addTarget:self action:@selector(onClick) forControlEvents:UIControlEventTouchUpInside];
    btn.backgroundColor = [UIColor redColor];
    [self.view addSubview:btn];
}

- (void)onClick
{
//    NSLog(@"被点了");
    UIApplication *app = [UIApplication sharedApplication];
    // 设置应用程序图标上的数字
//    app.applicationIconBadgeNumber = 998;
    // 设置状态栏的联网动画
//    app.networkActivityIndicatorVisible = YES;

    // 设置状态栏的样式
    // app.statusBarStyle = UIStatusBarStyleLightContent;
//    [app setStatusBarStyle:UIStatusBarStyleLightContent animated:YES];

    // 设置状态栏是否隐藏
//    app.statusBarHidden = YES;
//    [app setStatusBarHidden:YES withAnimation:UIStatusBarAnimationFade];

    /*
     URL:统一资源定位符 , 用来唯一的表示一个资源
     URL: 协议头://主机地址/资源路径

     网络资源:http://www.baidu.com/images/20140603/abc.png
     本地资源:file:///users/apple/desktop/abc.png
     */

    NSURL *url = [NSURL URLWithString:@"http://ios.itcast.cn"];
    [app openURL:url];
}

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

//- (BOOL)prefersStatusBarHidden
//{
//    return YES;
//}