将ViewController添加为子视图时，不会显示UIImageView

Question

My main aim is to have one background for all of my ViewControllers . Every ViewController I have has a clear background.

To do this, I have made one UIViewController (called backgroundViewController ) that will act as the subview to all my other ViewControllers . It has one UIImageView which displays this particular background. I will then add this backgroundViewController as a subview of all my other ViewControllers .

The problem is - this imageView won't show as a subview!

This is how I display the imageView :

- (void)viewDidLoad
{


    if ([musicPlayer playbackState] == MPMusicPlaybackStateStopped) {

        UIImage *artworkBackgroundView;

        artworkBackgroundView = [UIImage imageNamed:@"noArtworkBackground"];

        UIImage *effectImage = nil;

        backgroundView.image = effectImage;

        [backgroundView setImage:artworkBackgroundView];
        backgroundView.image = effectImage;
    }
}

- (void) handle_NowPlayingItemChanged: (id) notification
{

    if ([musicPlayer playbackState] != MPMusicPlaybackStateStopped) {

// Get artwork for current now playing item
        MPMediaItem *currentItem = [musicPlayer nowPlayingItem];

        MPMediaItemArtwork *artwork = [currentItem valueForProperty: MPMediaItemPropertyArtwork];

        UIImage *artworkBackgroundView = [artwork imageWithSize: CGSizeMake(618, 618)];

        if (!artworkImage) {
            artworkBackgroundView = [UIImage imageNamed:@"noArtworkBackground"];
            artworkImage = [UIImage imageNamed:@"noArtwork"];
        }

        [backgroundView setImage:artworkBackgroundView];            
    }
}

As you can see, backgroundView changes each time the music player skips song.

To test that backgroundViewController does show as a subview, I added another imageView and changed its image to a static .png in Interface Builder, and that shows correctly as a subview .

This is how I make it a subview for other ViewControllers :

backgroundViewController *backgroundVC = [[backgroundViewController alloc] initWithNibName:@"backgroundViewController" bundle:nil];

[self.view insertSubview:backgroundVC.view atIndex:0];

What I want is the UIImageView called backgroundView to show up when it is being called as subview.

I have tested that backgroundView does change according to what song is playing, and it works correctly.

What am I doing wrong? backgroundView refuses to show up as a subview ?! I've searched a ton about adding ViewControllers as subviews but I can't find a similar problem.

Any help would be much appreciated, thanks! :)

Answer 1

This worked for me:

backgroundViewController *backgroundVC = [[backgroundViewController alloc] initWithNibName:@"backgroundViewController" bundle:nil];

[self addChildViewController:backgroundVC];
[self.view addSubview:backgroundVC.view];

I found the solution here . I need to read more about 'Custom Containers'.