检查远程通知是否开启 http://stackoverflow.com/questions/1535403/determine-on-iphone-if-user-has-enabled-push-notifications

gistfile1.m

- (BOOL)checkNotificationIsEnabled {
    UIApplication *application = [UIApplication sharedApplication];
    BOOL enabled = NO;
    // iOS8 and above
    if ([application respondsToSelector:@selector(isRegisteredForRemoteNotifications)]) {
        if ([application isRegisteredForRemoteNotifications]) {
            UIUserNotificationSettings *settings = [[UIApplication sharedApplication] currentUserNotificationSettings];
            if (settings.types != UIUserNotificationTypeNone) {
                enabled = YES;
            }
        }
    }
    else {
        UIRemoteNotificationType types = [[UIApplication sharedApplication] enabledRemoteNotificationTypes];
        if (types != UIRemoteNotificationTypeNone) {
            enabled = YES;
        }
    }
    
    NSLog(@"APNS is %@", @(enabled));
    
    return enabled;
}