Understanding the Crash Issue with UIActivityViewController on iOS 8 iPads

The UIActivityViewController class is a powerful tool within iOS that developers often utilize to present various services to users, such as sharing or copying content. However, under specific conditions in iOS 8, developers encountered a troublesome bug causing the UIActivityViewController to crash on iPad devices. This issue severely impacts the user experience and poses significant challenges in app development and maintenance for older iOS versions.

Technical Background

To better understand why UIActivityViewController might crash on iOS 8 iPads, it is essential to delve into the class's functioning. This controller is responsible for presenting various sharing actions in a standard modal interface. On iPads, this typically gets displayed in a popover.

Reasons for the Crash

1. Popover Presentation:
   • On an iPad, UIActivityViewController is shown in a popover, unlike iPhones, where a full-screen modal view is used.
   • In iOS 8, there were bugs in the popover presentation logic that caused instability, especially when the sourceView or sourceRect weren't set correctly.
2. Missing Source Information:
   • iOS 8 requires explicit specification of the sourceView or sourceRect for the popover. Failing to do so may lead to a UIPopoverPresentationController crash because the presentation logic lacks context on how to display the popover correctly.
3. Transition Handling:
   • Incorrect handling during the transition between the view controller states can lead to an unexpected state causing a crash.

Example Code

1UIActivityViewController *activityViewController = [[UIActivityViewController alloc] initWithActivityItems:@[textToShare] applicationActivities:nil];
2
3// Correct popover presentation on iPad
4activityViewController.popoverPresentationController.sourceView = self.view; // ensure this is set
5activityViewController.popoverPresentationController.sourceRect = CGRectMake(self.view.bounds.size.width/2.0, self.view.bounds.size.height/4.0, 1.0, 1.0);
6
7[self presentViewController:activityViewController animated:YES completion:nil];

Troubleshooting and Fixes

Developers dealing with this issue on iOS 8 might consider several strategies to mitigate it:

1. Ensure Source Provision:
   • Always assign both sourceView and sourceRect to the popoverPresentationController when working with iPads.
2. Conditional Code Logic:
   • Implement OS version checks to apply specific logic only for iOS 8 using tools like NSProcessInfo.
3. Update to Latest iOS 8.x:
   • Encourage users to update to the latest version of iOS 8 where possible, as some of these issues were eventually addressed in later point releases.
4. User Experience Adjustments:
   • Consider creating a custom sharing interface specific to iPads that bypasses UIActivityViewController if issues persist.

Key Points Summary

Conclusion

The UIActivityViewController crashes on iOS 8 iPads highlight a unique challenge in developing for older versions of iOS. By properly configuring popover presentation parameters and adopting alternative strategies when necessary, developers can maintain app stability and provide a seamless user experience. Understanding these nuances is crucial for continuing to support iOS 8 users without compromising the app’s functionality or user satisfaction.