ios8 iPad uiwebview crashes while displaying popov

问题:

On ios8 and iPad if a uiwebview is displaying a HTML page containing a drop down list

eg this page http://www.w3schools.com/tags/tryit.asp?filename=tryhtml_select

then

• repeatedly tap on the HTML drop down list that contain lists of cars . first item is Volvo.
• tap every 1/2 second or so that uipopover opens and closes
• app will crash:

Terminating app due to uncaught exception 'NSGenericException', reason: 'UIPopoverPresentationController () should have a non-nil sourceView or barButtonItem set before the presentation occurs.'

Is there anyway to work around this in uiwebview in ios8?

It doesn't happen using wkwebview, but I would like to fix it in uiwebview.

Update: This seems to help but unsure of side effects. I have overridden the following in the view controller that contains the uiwebview.

-(void)dismissViewControllerAnimated:(BOOL)flag completion:(void (^)(void))completion
{
    if (completion)
    {
        completion();
    }

    [super dismissViewControllerAnimated:NO completion:nil];
}

回答1:

The solution mentioned in the question did not help me, however it did point me in the right direction. After some investigation I would say it's some sort of race condition between presenting and removing the popover. As a workaround you can postpone the presentation in the delegate of the UIWebView:

-(void)presentViewController:(UIViewController *)viewControllerToPresent animated:(BOOL)flag completion:(void (^)(void))completion
{
    dispatch_after(dispatch_time(DISPATCH_TIME_NOW, NSEC_PER_USEC), dispatch_get_main_queue(),
               ^{
                   [super presentViewController:viewControllerToPresent animated:flag completion:completion];
               });
}

回答2:

The previous solutions did not help me.

There is a bug already logged to Apple (see openradar) for this.

The issue seems to be that the web view tries to present a view controller in a popover without setting the sourceView of the popover. Although it's definitely an Apple issue I have used the following workaround to avoid my app to crash:

- (void)presentViewController:(UIViewController *)viewControllerToPresent animated:(BOOL)flag completion:(void (^)(void))completion
{
    // Override this method in the view controller that owns the web view - the web view will try to present on this view controller ;)

    if (viewControllerToPresent.popoverPresentationController && !viewControllerToPresent.popoverPresentationController.sourceView) {
        return;
    }

    [super presentViewController:viewControllerToPresent animated:flag completion:completion];
}

回答3:

I worked around it in the following way after noticing that sourceView is set in the cases where it crashes:

-(void)presentViewController:(UIViewController *)viewControllerToPresent animated:(BOOL)flag completion:(void (^)(void))completion {

  UIPopoverPresentationController* pres = viewControllerToPresent.popoverPresentationController;

  if(pres.sourceView) {
    //log the fact you are ignoring the call
  }
  else {
    [super presentViewController:viewControllerToPresent animated:flag completion:completion];
  }
}

回答4:

I had different exception in the same scenario, and none of workarounds from here helped me.

This was my exception:

Terminating app due to uncaught exception 'NSRangeException', reason: '-[UITableView _contentOffsetForScrollingToRowAtIndexPath:atScrollPosition:]: row (4) beyond bounds (0) for section (0).'

This is code I used to workaround it:

-(void)presentViewController:(UIViewController *)viewControllerToPresent animated:(BOOL)flag completion:(void (^)(void))completion {
    if ([viewControllerToPresent respondsToSelector:NSSelectorFromString(@"_cachedItems")]) {
        if([viewControllerToPresent valueForKey:@"_cachedItems"] == nil) {
            if (completion != nil) {
                completion();
            }
            return;
        }
    }

    [super presentViewController:viewControllerToPresent animated:flag completion:completion];
}

It's very nasty workaround that prevents from showing dropdown in cases when it's about to crash, and this solution can stop working in any time as it uses internal properties. However it was the only solution that worked for me so maybe it will be helpful for someone.

回答5:

I have decreased the probability of occurrence of crash in this way.. Used javascript code and native ios

Web Side code changes

1. Register a 'click' event listener to your html component(drop down).
2. In the call back method send notification to native code. ex : "window.location='fromJavaScript://PopoverIssue'; "
3. It will call uiwebviews shouldStartLoadWithRequest

Native Side code changes

1. Implement UIPopoverPresentationControllerDelegate protocol on viewcontroller which has uiwebview and over ride popoverPresentationControllerShouldDismissPopover popoverPresentationControllerDidDismissPopover
2. put below code in shouldStartLoadWithRequest method of uiwebview for the above click notification

   [[UIApplication sharedApplication] beginIgnoringInteractionEvents];
       self.popoverPresentationController = self.presentedViewController.popoverPresentationController;
       self.existedPopoverDelegate = [self.popoverPresentationController delegate];
       self.popoverPresentationController.delegate = self;
       dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0);
       dispatch_async(queue, ^{
           int64_t delay = 2.0;
           dispatch_time_t time = dispatch_time(DISPATCH_TIME_NOW, delay * NSEC_PER_SEC);
           dispatch_after(time, dispatch_get_main_queue(), ^{
               if([[UIApplication sharedApplication] isIgnoringInteractionEvents])
               {
                   [[UIApplication sharedApplication] endIgnoringInteractionEvents];
               }
           });
       });

3. implement the overridden protocol methods as follows

   
   
   
   (BOOL)popoverPresentationControllerShouldDismissPopover:(UIPopoverPresentationController *)popoverPresentationController
   {
   [self.existedPopoverDelegate popoverPresentationControllerShouldDismissPopover:popoverPresentationController];
   return YES;
   }
   (void)popoverPresentationControllerDidDismissPopover:(UIPopoverPresentationController *)popoverPresentationController
   {
   [self.existedPopoverDelegate popoverPresentationControllerDidDismissPopover:popoverPresentationController];
   dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0);
   dispatch_async(queue, ^{
   int64_t delay = 2.0;
   dispatch_time_t time = dispatch_time(DISPATCH_TIME_NOW, delay * NSEC_PER_SEC);
   dispatch_after(time, dispatch_get_main_queue(), ^{
       if([[UIApplication sharedApplication] isIgnoringInteractionEvents])
       {
           [[UIApplication sharedApplication] endIgnoringInteractionEvents];
       }
   });
   });
   }
   

Hope it will help to decrease the crash occurrence .