How to use UIApplicationDidBecomeActiveNotification

Question

How to use UIApplicationDidBecomeActiveNotification?

Should I declare it in viewDidLoad or viewWillAppear to reload data when coming from background to foreground.

Does UIApplicationDidBecomeActiveNotification gets called only when app comes from background to foreground?

Please help. Thanks.

Answer 1

Sometimes it is useful to have a listener of UIApplicationDidBecomeActiveNotification when you need to make some action in your view controller on wake up from background (in case you entered to background with this view controller on-screen). In such wake up viewWillAppear will not be triggered!

Example of use:

- (void)viewWillAppear:(BOOL)animated
{
    [super viewWillAppear:animated];

    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(someMethod)     name:UIApplicationDidBecomeActiveNotification object:nil];
}


- (void)viewWillDisappear:(BOOL)animated
{
    [super viewWillDisappear:animated];

    [[NSNotificationCenter defaultCenter] removeObserver:self name:UIApplicationDidBecomeActiveNotification object:nil];

}

- (void)someMethod
{
    <YOUR CODE AT WAKE UP FROM BACKGROUND>
}

Of course, you can also implement all you need at your app delegate class life cycle.