Present a transparent modal UIViewController

Question

I'm trying to make a custom alertView (for iOS7+) on my own but I struggle with the alertView presentation.

I have a UIViewController with a black background (alpha set to 0.25f), and a alertView as subview.

When I want to show the alertView, I present modally the viewController:

-(void) show 
{
    UIWindow* window = [[UIApplication sharedApplication] keyWindow];
    self.modalTransitionStyle = UIModalPresentationCustom;
    self.transitioningDelegate = self;
    [window.rootViewController presentViewController:self animated:YES completion:nil];
}

And here is my animator object:

-(NSTimeInterval) transitionDuration:(id<UIViewControllerContextTransitioning>)transitionContext
{
    NSLog(@"%s",__PRETTY_FUNCTION__);
    return 2;
}

-(void) animateTransition:(id<UIViewControllerContextTransitioning>)transitionContext
{
    NSLog(@"%s",__PRETTY_FUNCTION__);

    UIView* toView = [transitionContext viewForKey:UITransitionContextToViewKey];
    toView.alpha = 0;

    UIView* container = [transitionContext containerView];
    [container addSubview:toView];

    [UIView animateWithDuration:[self transitionDuration:transitionContext] animations:^{
        toView.alpha = 0.5;
    } completion:^(BOOL finished) {
        [transitionContext completeTransition:YES];
    }];
}

The thing is: the modal VC is fading with the presenting VC in background as its supposed to do, but when the animation ends the presenting VC is removed from the background.

If I call [transitionContext completeTransition:YES]; instead, the presenting VC is in background but the modal VC is removed at animation end, so I guess the context cancels the presentation if we send 'NO'.

Is there a way to keep the presenting VC in background without having to make a snapshot of it and set it as background of the modal VC's view?

Answer 1

I've tried this solution and it works on both iOS 7 and 8:

if ([[UIDevice currentDevice].systemVersion integerValue] >= 8)
{
    //For iOS 8
    presentingViewController.providesPresentationContextTransitionStyle = YES;
    presentingViewController.definesPresentationContext = YES;
    presentedViewController.modalPresentationStyle = UIModalPresentationOverCurrentContext;
}
else
{
    //For iOS 7
    presentingViewController.modalPresentationStyle = UIModalPresentationCurrentContext;
}

Note: Be aware of the difference between 'presentingViewController' and 'presentedViewController'.