I add this function to post a notification when the app enter foreground:

- (void)applicationWillEnterForeground:(UIApplication *)application
{
    [[NSNotificationCenter defaultCenter] postNotificationName: @"UIApplicationWillEnterForegroundNotification" object: nil];
}

In my own class:

- (void) handleEnterForeground: (NSNotification*) sender
{
    [self reloadTableData];
}


- (void)viewDidLoad
{
    [super viewDidLoad];
    [[NSNotificationCenter defaultCenter] addObserver: self
                                         selector: @selector(handleEnterForeground:)
                                             name: @"UIApplicationWillEnterForegroundNotification"
                                           object: nil];
}

but the handleEnterForeground: function will called twice, I don't know why. The reloadTableData: function will call remote webService , so when the app enter foreground, it will stuck for a while.

有帮助吗?

解决方案

The system will call that event automatically. The reason it fires twice is because you manually fire it again.

P.S. It's better to use the variable name UIApplicationWillEnterForeground, instead of a NSString literal.

EDIT: I realize now the confusion is coming from the fact that you didn't know that this even name was already taken. As a note to other people who run into this kind of problem, it is a good practice to prefix your event names with your project prefix (i.e. XYZEventNotification) to avoid collisions.

许可以下: CC-BY-SA归因
不隶属于 StackOverflow
scroll top