Display UIView while waiting for main view to load? - ios

Question

So I am trying to create somewhat of a loading screen in my application. I have a view that takes 3-10 seconds to load. During this time I want to display a UIView that I made that is simply black with a loading screen. Currently I am putting my code inside of the viewDidLoad function just after super viewDidLoad. Here is my code
UIView* baseView = [[UIView alloc] initWithFrame:[[UIScreen mainScreen] applicationFrame]];
[self.view addSubview:baseView];
[baseView setBackgroundColor:[UIColor blackColor]];
[self.view bringSubviewToFront:baseView];
baseView.layer.zPosition = 1;
This works and creates my view overtop of everything exactly how I want it, however this waits until my main view is completely done loading before it actually shows anything. Is viewDidLoad not a good place to put this and if so where should I put it.
Simply put I have a very basic UIView that I want to load while I wait for the actual view to load and then simply hide it. Any ideas how to do this?

Answer 1

You need to dispatch your hard work on another thread, otherwise the OS will wait until all the process is done before refreshing the UI (that's why you see your loading screen appear only after 3-10 seconds).
Don't forget to dispatch back on the main thread after the lengthy job is done. All UI updates must be done on the main thread.
self.loadingView.hidden = NO;
// Dispatch lengthy stuff on another thread
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0), ^{
// Do lengthy stuff here
// Dispatch back on the main thread (mandatory for UI updates)
dispatch_async(dispatch_get_main_queue(), ^{
self.loadingView.hidden = YES;
});
});

Answer 2

UIView* baseView = [[UIView alloc] initWithFrame:[[UIScreen mainScreen] applicationFrame]];
[self.view addSubview:baseView];
[baseView setBackgroundColor:[UIColor blackColor]];
[self.view bringSubviewToFront:baseView];
baseView.layer.zPosition = 1;
//Create new dispatch for load data
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0), ^{
// Load data in here
// Call main thread to update UI
dispatch_async(dispatch_get_main_queue(), ^{
baseView.hidden = YES;
});
});