App freeze while Schedule LocalNotifications in background

Question

- (void)applicationDidEnterBackground:(UIApplication *)application
{
    for (int i =0; i<30; i++){
       //add a local notification and schedule it
    }
}

when app switch to background, these codes will freeze app in a while.

Answer 1

There's no document about UIApplication is thread safe or not.
After a long time test I found most time execute LocalNotification on background works well. but some times it just crash our app.

So it seems like all the class with 'UI' prefixed are not thread safe and you should never invoke there's methods on another thread.

And my solution is reduced the number of LocalNotification, it still freeze app in a bit, but we thing we can accept this little freeze.