FIX: A blank view appears after QLPreviewController dismissed in iOS 7

Recently when I am working with iOS 7, I encounter the following problem: If the modalPresentationStyle of an view controller is set as UIModalPresentationFormSheet or UIModalPresentationPageSheet and after one uses the QLPreviewController once in the view controller and dismisses the Quick Look, a blank / gray view will appear on the screen instead of the presented view controller. This blank view cannot be dismissed or interacted.

That seems a serious bug in iOS 7. :(

After some days trying errors, I've found the following workaround:

in the presenting ViewController:

if ([self DeviceSystemMajorVersion] >= 7) {

modalVC.transitioningDelegate = self;

modalVC.modalPresentationStyle = UIModalPresentationCustom;

} else {

modalVC.modalPresentationStyle = UIModalPresentationFormSheet;

}

The function to detect iOS 7:

- (NSUInteger) DeviceSystemMajorVersion {

    static NSUInteger _deviceSystemMajorVersion = -1;

    static dispatch_once_t onceToken;

dispatch_once(&onceToken, ^{

  _deviceSystemMajorVersion = [[[[[UIDevice currentDevice] systemVersion] componentsSeparatedByString:@"."] objectAtIndex:0] intValue];

 });

return _deviceSystemMajorVersion;

}

The presenting view controller should conform to the protocol UIViewControllerAnimatedTransitioning and UIViewControllerTransitioningDelegate, in order to use the custom transaction style that indroduced in iOS 7. Continue to add these methods:

- (id<UIViewControllerAnimatedTransitioning>)animationControllerForPresentedController:(UIViewController *)presented

                                                                  presentingController:(UIViewController *)presenting

                                                                      sourceController:(UIViewController *)source {

return self;

}

- (void)animateTransition:(id <UIViewControllerContextTransitioning>)transitionContext {

UIView *inView = [transitionContext containerView];

    UIView *toView = [transitionContext viewControllerForKey:UITransitionContextToViewControllerKey].view;

    UIView *fromView = [transitionContext viewControllerForKey:UITransitionContextFromViewControllerKey].view;

 

 UIView *preferenceOverlay = [[UIView alloc] initWithFrame:inView.frame];

 preferenceOverlay.backgroundColor = [UIColor blackColor];

 preferenceOverlay.alpha = 0;

 [inView addSubview:preferenceOverlay];



 toView.frame = CGRectMake(0, 0, 540, 540);

 toView.center = CGPointMake(CGRectGetMidX(inView.frame), CGRectGetMidY(inView.frame));



 [inView addSubview:toView];

 

    [UIView animateKeyframesWithDuration:(1.0) delay:0 options:0 animations:^{

  preferenceOverlay.alpha = 0.4;

    } completion:^(BOOL finished) {

        [transitionContext completeTransition:finished];

    }];

}

Then in the presented view controller:

-(void)viewWillLayoutSubviews {

 [super viewWillLayoutSubviews];



if ([self DeviceSystemMajorVersion] >= 7) {

if (QLOpened) {

self.view.frame = CGRectMake(0, 0, 540, 540);

CGFloat xCenter = CGRectGetMidX(self.view.superview.frame) + 125;

CGFloat yCenter = CGRectGetMidY(self.view.superview.frame) - 125;

self.view.center = CGPointMake(xCenter, yCenter);

   NSLog(@"Center X:%f Y:%f",xCenter,yCenter);

  }

 }

}

Then let the view controller to conform the protocol QLPreviewControllerDelegate and add the following method:

- (void)previewControllerWillDismiss:(QLPreviewController *)controller {

NSLog(@"QLView dismissed");

 [self.view setNeedsLayout];

}

DONE!

If you have the centering problem of the modal view controller, try fine-tuning the center point of the method viewWillLayoutSubviews