Question

I’m copying a database I include in my bundle with my app and transferring it to the Documents directory to make it writeable. It takes some time and I we currently have just a splash screen. Is there a way to put a “Loading…” alert or some sort of activity indicator (Like how Words With Friends does it when loading your games), to give the user some context as to what’s happening for the first 20 seconds the first time they open the app? I didn’t know if I had a reference to that screen somehow since the first viewController that gets presented from the AppDelegate is not loaded yet. Thanks.

Answer 1

When performing long running tasks on application launch there are a few considerations.

Application Did Finish Launching

You must finish the - (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions within a certain amount of time, which I believe is 20 seconds, otherwise your application will get shut down from the watchdog

Note On WatchDog Crashes

What I usually do is create a LoaderViewController and add it as a subview of the window. I still set the root view controller of the application to the first view controller though. this essentially hands off loading control to the loader view controller to perform your functions.

Although this is sometime frowned upon by Apple’s Human Interface Guidelines

Avoid displaying an About window, a splash screen, or providing any
other type of startup experience that prevents people from using your
application immediately.

iOS Human Interface Guidelines

Non Blocking

You’re also going to want to perform all your copying in the background using GrandCentral Dispatch or use - (void)performSelectorInBackground:(SEL)aSelector withObject:(id)arg to prevent blocking the main thread. This way you can present a UIActivityIndicatorView that remains spinning while the task is being performed.

Grand Central Dispatch

Grand Central Dispatch is probably the best way to handle this. You can perform your task in the background and update the main thread, like a UIProgressView in the same block like this

dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
        //Do something in background
        dispatch_async(dispatch_get_main_queue(), ^{
            //Update UI
        });
    });

Once finished, remove your LoaderViewController [loaderViewController removeFromSuperview]; and your application will go to the first controller. At this time you can also refresh the UI to display updated information.

Grand Central Dispatch Reference