Activity indicator in a UITabBar application on the iPhone

Question

Hi,

I have a UITabBar + UINavigationController application which often needs data from the internet. Sometimes it takes quite a while before it gets it, so I would like to show an activity indicator.

What I was trying is to add a activityView to my window in my applicationDidFinishLaunching method:

[window addSubview:tabBarController.view];
fullscreenLoadingView.hidden = YES;
[window addSubview:fullscreenLoadingView];

And then I add the application delegate as a observer to the default notification center:

[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(startFullscreenLoading:) name:@"startFullscreenLoading" object:nil];
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(stopFullscreenLoading:) name:@"stopFullscreenLoading" object:nil];

and implement the methods:

- (void)startFullscreenLoading:(NSNotification *)notification {
    fullscreenLoadingView.hidden = NO;
}

- (void)stopFullscreenLoading:(NSNotification *)notification {
    fullscreenLoadingView.hidden = YES;
}

When I then use this directly in the applicationDidFinishLaunching method the loading indicator view shows upp as expected:

[[NSNotificationCenter defaultCenter] postNotificationName:@"startFullscreenLoading" object:self];

But when I use it from one of the navigation controllers the startFullscreenLoading: method is called but I don't see the loading indicator view. Why is that?

Answer 1

The most likely thing I can guess is that your indicator view is below some other view. Try

[[fullScreenLoadingView superView] bringSubviewToFront:fullScreenLoadingView]

If that doesn't work, I would suggest breaking inside of -startFullscreenLoading to make sure the fullscreenLoadingView is still valid.

Answer 2

Are you loading your data on a background thread? Your main thread will be blocked & won't be able to redraw or process any other events.

Answer 3

In my app I did this by adding the UIActivityView in IB and making sure it was above everything else (as a top-level object). It's set to be invisible when stopped.

Then in my code I make it appear with [activityIndicator startAnimating] and make it disappear with [activityIndicator stopAnimating];