iOS: Modal ViewController with transparent background

Question

I'm trying to present a view controller modally, with a transparent background. My goal is to let both the presenting and presented view controllers's view to be displayed at the same time. The problem is, when the presenting animation finishes, the presenting view controller's view disappears.

- (IBAction)pushModalViewControllerButtonPressed:(id)sender
{
    ModalViewController *modalVC = [[ModalViewController alloc] init];
    [self presentViewController:modalVC animated:YES completion:nil];
}

I know I could just add the view as a subview, but I'd like to avoid this solution for some reason. How could I fix it?

Answer 1

For those trying to get this to work in iOS 8, the "Apple-approved" way to display a transparent modal view controller is by setting modalPresentationStyle on the presented controller to UIModalPresentationOverCurrentContext.

This can be done in code, or by setting the properties of the segue in the storyboard.

From the UIViewController documentation:

UIModalPresentationOverCurrentContext

A presentation style where the content is displayed over only the parent view controller’s content. The views beneath the presented content are not removed from the view hierarchy when the presentation finishes. So if the presented view controller does not fill the screen with opaque content, the underlying content shows through.

When presenting a view controller in a popover, this presentation style is supported only if the transition style is UIModalTransitionStyleCoverVertical. Attempting to use a different transition style triggers an exception. However, you may use other transition styles (except the partial curl transition) if the parent view controller is not in a popover.

Available in iOS 8.0 and later.

https://developer.apple.com/documentation/uikit/uiviewcontroller

The 'View Controller Advancements in iOS 8' video from WWDC 2014 goes into this in some detail.

Note:

• Be sure to give your presented view controller a clear background color, lest it not actually be see-through!
• You have to set this before presenting ie setting this parameter in the viewDidLoad of the presentedViewController won't have any affect