在IOS7中设置applicationIconBadgeNumber不会有什么问题，但是直接在IOS8中设置applicationIconBadgeNumber会报错。因为在IOS8中要想设置applicationIconBadgeNumber，需要用户的授权，在IOS8中，需要加上下面的代码：

UIUserNotificationSettings *settings = [UIUserNotificationSettings settingsForTypes:UIUserNotificationTypeBadge categories:nil];[[UIApplication sharedApplication] registerUserNotificationSettings:settings];

但是这两句如果是在IOS7的系统中运行的话就会报错，所以需要先判断IOS的版本，完整代码如下：

float version = [[[UIDevice currentDevice] systemVersion] floatValue];    if (version >= 8.0) {    UIUserNotificationSettings *settings = [UIUserNotificationSettings settingsForTypes:UIUserNotificationTypeBadge categories:nil];    [[UIApplication sharedApplication] registerUserNotificationSettings:settings];}

如果是注册消息推送的话，需要这样写：

float version = [[[UIDevice currentDevice] systemVersion] floatValue];if (version >= 8.0) {    UIUserNotificationSettings *settings = [UIUserNotificationSettings settingsForTypes:UIUserNotificationTypeBadge categories:nil];    [[UIApplication sharedApplication] registerUserNotificationSettings:settings];    [application registerForRemoteNotifications];}