Preventing view from unloading in iOS SDK?

Question

I've built an app that uses a UITableView inside a UINavigationController, inside a UITabBarController. Every entry in the UITableView opens up a view that contains some basic text, buttons, but most importantly, an MPMoviePlayerController that plays audio when started. A user can click this MPMoviePlayerController and continue to browse around the rest of the app (different tabs, or moving back in the navcontroller, opening other views from the tableview) and continue to hear the audio.

I'd like the user to be able to return to the view with the active MPMoviePlayerController at any time. I understand how I would go about allowing the user to return to a certain view from any view, but I'm struggling with how to prevent that view from being reloaded when the user tries accessing the same view.

Is there any way I can save a view in memory? Or save the active MPMoviePlayerController as some type of global object, so that I can at least access that from anywhere?

I appreciate any and all help. Thanks!

Answer 1

I'd recommend you create a property for the MPMoviePlayerController in your app's UIApplicationDelegate (which you can then access from anywhere in the code with [UIApplication sharedApplication].delegate but you will need to cast to your UIApplicationDelegate subclass).

When you come to enter the screen which plays content, check whether your movie player property in the app delegate is nil, if it is create it, otherwise re-use it.

Don't forget to release the reference to your MPMoviePlayerController when the media stops playing, or when the media has already stopped and you get a memory warning or when your app shuts down.

The down side of this approach is it causes coupling between most of your view controllers and your app delegate. You could mitigate this with the use of a protocol however.

Answer 2

A little bit of a hack, but you can override setView: in your subclass so that it never allows to set the view to nil:

-(void)setView:(UIView *)view
{
    if (view == nil) return;

    [super setView:view];
}

Answer 3

You should simply retain it. Like this [myView retain] and keep a pointer to it in where you need. When you want myView to appear, just add it as a subview to current visible view like[myController.view addSubview:myView].

Hope that will help, Good luck!

Answer 4

I've found that even adding a retain doesn't do the trick. I've actually found the best success with overriding the setView (since part of unloading the view involves calling setView:nil. I have a BOOL that gets set the FIRST time the VC loads and once thats set it will never allow setView to be called again.

- (void) setView: (UIView*) view{
  NSLog(@"MainViewController: setView");

  // this is our attempt to stop iOS from unloading our view.. when iOS tries to unload your view they call setView:nil.. so, no!
  if(!viewDidAppear) [super setView:view];
}