iOS 13.4 Beta 4 - crash

Hi, I am encountering a similar problem, in my case it's triggered when closing a view controller and setting rootViewController on the UIWindow.

Were you able to find the cause of the issue ?

I have same crash. In my case, the UIToolbar is crashing the app, laying out its internal items.

Radar # FB7654080

iOS 13.4 UIToolbar crashes app inside call to _layoutBar() ========

This bug only occurs in iOS 13.4. It does not iOS 13.3 and earlier. Verified in Simulator.

Because this bug makes the app unusable, the app has been Removed from Sale on the App store.

This crash occurs when the user clicks on a Tab button to switch to a different Tab view. If that Tab view has a toolbar, with several operating modes, where its toolbar item sets have to be swapped out by viewWillAppear(), the app will crash.

The crash occurs while UIKit is laying out all the subviews in the upcoming Tab view. This is all 100% Apple code. My own functions are not in the crash callback list.

It is 100% repeatable, but sometimes it takes several attempts. For instance, my app has these 2 tabs (among others): File and Favorites.

If the user has a document open in the Files tab and then switches back and forth to Favorites, then back to File tab, ....

It takes 2 or 3 repeats of tab switching to cause the crash.

It looks like UIKit is holding on to the prior count of UIToolbarItems, which does not match the "actual" number of items. And then it inserts items into an out-of-bounds index. CRASH !

So the fix is simple, UIButtonBar._layoutBar() needs to check the actual upper bound index before the insertion.

*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: 'index out of bounds for arranged subview: index = 5 expected to be less than or equal to 4'

*** First throw call stack:

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After investigating, I have determined that in my case the crash was caused by setting duplicate (same instance) UIBarButtonItem items in rightBarButtonItems or leftBarButtonItems (for example for spacing purposes)

Fixed by creating unique instances

@Tiberiu891 pointed the problem. You should be careful when adding items to the toolbar. The same instances added several times cause this strange crash. Here is an example:

NSMutableArray* items = [self.toolbar.items mutableCopy];
[items addObject:self.fixedSpaceButton];
//...
[self.toolbar setItems:items];

The correct way doing this is:

NSMutableArray* items = [self.toolbar.items mutableCopy];
if(![items containsObject:self.fixedSpaceButton]) {
    [items addObject:self.fixedSpaceButton];
}
//...
[self.toolbar setItems:items];