注册远程通知时iOS7崩溃

这在iOS8中运行良好,但是当我把它放在iOS7设备上时,它会崩溃,从而导致错误

-[UIApplication registerUserNotificationSettings:]: unrecognized selector sent to instance 0x14e56e20

我正在AppDelegate中注册通知：

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {

#ifdef __IPHONE_8_0
    UIUserNotificationSettings *settings = [UIUserNotificationSettings settingsForTypes:(UIRemoteNotificationTypeBadge
                                                                                         |UIRemoteNotificationTypeSound
                                                                                         |UIRemoteNotificationTypeAlert) categories:nil];
    [[UIApplication sharedApplication] registerUserNotificationSettings:settings];
#else
    //register to receive notifications
    UIRemoteNotificationType myTypes = UIRemoteNotificationTypeBadge | UIRemoteNotificationTypeAlert | UIRemoteNotificationTypeSound;
    [[UIApplication sharedApplication] registerForRemoteNotificationTypes:myTypes];
#endif

    application.applicationIconBadgeNumber = 0;

    return YES;
}

当我设置断点时,它总是运行__IPHONE_8_0块中的代码.我怎么能检测到哪个块运行？

你不应该像这样使用预处理器.更好的方法是检查您的对象是否响应您发送的消息,而不是检查操作系统版本.将您的方法更改为

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {

    if ([application respondsToSelector:@selector(registerUserNotificationSettings:)])
    {
        UIUserNotificationSettings *settings = [UIUserNotificationSettings settingsForTypes:(UIRemoteNotificationTypeBadge
                                                                                             |UIRemoteNotificationTypeSound
                                                                                             |UIRemoteNotificationTypeAlert) categories:nil];
        [application registerUserNotificationSettings:settings];
    }
    else
    {
        //register to receive notifications
        UIRemoteNotificationType myTypes = UIRemoteNotificationTypeBadge | UIRemoteNotificationTypeAlert | UIRemoteNotificationTypeSound;
        [application registerForRemoteNotificationTypes:myTypes];
    }
    application.applicationIconBadgeNumber = 0;

    return YES;
}

这里有几点需要注意.我将[UIApplication sharedApplication]更改为应用程序,因为委托已经在您的UIApplication实例中传递,因此只需直接访问它.

respondsToSelector：是来自NSObject的一个方法,它会告诉你接收者,应用程序是否会响应选择器(或方法).你只需要像@selector(myMethod :)那样包装方法来检查它.在使用较新的API时,这是一种很好的做法,可以实现向后兼容性.在处理id类型的匿名对象时,您还希望进行此类检查.

至于为什么#ifdef __IPHONE_8_0不起作用,请查看以下答案：https://stackoverflow.com/a/25301879/544094