App crashes with low memory only on iPhone 8 iOS 14.4.1

Question

I am facing a weird error.

I have below method called on tapping a label. The method hides UIDatePicker. This is in UIViewController presented from collection view or table view.

this is in viewDidLoad()

self.StartDateLabel.addGestureRecognizer(UITapGestureRecognizer(target:self, action:#selector(self.startDateLabelTapped(_:))))

and this is the method called.Tapping the label first time shows the date picker so selector works but tapping again causes the issue. This happens on iPhone 8 only. I have tested on iPhone 11, 8 Plus. This is consistent behaviour.

I have one more such label for another date picker and same happens on that too.

What could be the reason?

@objc private func startDateLabelTapped(_ sender: Any) {
        
        if self.startDatePicker.isHidden {
    
            UIView.animate(withDuration: 0.3, delay: 0, options: [.transitionFlipFromLeft]) {
    
                DispatchQueue.main.async {
    
    
                    self.startDatePicker.isHidden = false
                }
            } //end of UIView.animate
        } else {
    
            UIView.animate(withDuration: 0.3, delay: 0, options: [.transitionFlipFromRight]) {
    
                DispatchQueue.main.async {
                    self.startDatePicker.isHidden = true //after this memory usage goes high and app crash with below stacktrace.
    
                }
            } //end of UIView.animate
    
        }
    }

Fatal Exception: NSInvalidArgumentException
0  CoreFoundation                 0x1818499d8 __exceptionPreprocess
1  libobjc.A.dylib                0x195bcfb54 objc_exception_throw
2  CoreFoundation                 0x181759bbc -[NSOrderedSet initWithSet:copyItems:]
3  UIKitCore                      0x1840e8d30 -[UIResponder doesNotRecognizeSelector:]
4  CoreFoundation                 0x18184c01c ___forwarding___
5  CoreFoundation                 0x18184df8c _CF_forwarding_prep_0
6  CoreFoundation                 0x1817ac370 __CFNOTIFICATIONCENTER_IS_CALLING_OUT_TO_AN_OBSERVER__
7  CoreFoundation                 0x1817ac330 ___CFXRegistrationPost_block_invoke
8  CoreFoundation                 0x1817ab928 _CFXRegistrationPost
9  CoreFoundation                 0x1817ab320 _CFXNotificationPost
10 Foundation                     0x1829e10a0 -[NSNotificationCenter postNotificationName:object:userInfo:]
11 Foundation                     0x182a62fa8 -[NSUbiquitousKeyValueStore _postDidChangeNotificationExternalChanges:sourceChangeCount:]
12 Foundation                     0x182be31e0 __53-[NSUbiquitousKeyValueStore _syncConcurrentlyForced:]_block_invoke_2
13 libdispatch.dylib              0x181481298 _dispatch_call_block_and_release
14 libdispatch.dylib              0x181482280 _dispatch_client_callout
15 libdispatch.dylib              0x1814645b0 _dispatch_main_queue_callback_4CF$VARIANT$armv81
16 CoreFoundation                 0x1817c95e0 __CFRUNLOOP_IS_SERVICING_THE_MAIN_DISPATCH_QUEUE__
17 CoreFoundation                 0x1817c3a88 __CFRunLoopRun
18 CoreFoundation                 0x1817c2ba0 CFRunLoopRunSpecific
19 GraphicsServices               0x19852b598 GSEventRunModal
20 UIKitCore                      0x1840b42f4 -[UIApplication _run]
21 UIKitCore                      0x1840b9874 UIApplicationMain
22 Lendable-Test                  0x10524ef38 main + 99 (AppDelegate.swift:99)
23 libdyld.dylib                  0x1814a1568 start

have checked with print statement after isHidden that the method is called. No app specific code is executed after it and The memory jumps executing some internal code. I can’t catch using breakpoint also as app crash due to memory.

Three screenshots from Instruments. I dont know how to analyse this data

memory leak

I get this stack trace when i pause just before memory tops out. Strangely my app works fine on iPhone 8 simulator but fails only on device !! I save added stack trace. i don't know why collection view related code is executed when i hide a control on another view.

#0  0x0000000195bcb498 in objc_msgSend ()
#1  0x00000001837a5d3c in __68-[NSCollectionLayoutSize _effectiveSizeForContainer:ignoringInsets:]_block_invoke ()
#2  0x00000001837a5c44 in -[NSCollectionLayoutSize _effectiveSizeForContainer:ignoringInsets:] ()
#3  0x00000001837d07a4 in -[_UICollectionLayoutItemSolver layoutFrame] ()
#4  0x00000001837d6ff0 in -[_UICollectionSolutionGroupArrangementItem initWithSolution:] ()
#5  0x00000001837d1764 in -[_UICollectionLayoutItemSolver _solveGroup] ()
#6  0x00000001837d0c64 in -[_UICollectionLayoutItemSolver _solveForContainer:layoutAxis:traitCollection:maxFrameCount:layoutRTL:preferredSizes:solutionRecursionDepth:] ()
#7  0x00000001837d1648 in -[_UICollectionLayoutItemSolver _solveGroup] ()
#8  0x00000001837d0c64 in -[_UICollectionLayoutItemSolver _solveForContainer:layoutAxis:traitCollection:maxFrameCount:layoutRTL:preferredSizes:solutionRecursionDepth:] ()
#9  0x00000001837cf92c in -[_UICollectionLayoutItemSolver solveForContainer:layoutAxis:traitCollection:maxFrameCount:layoutRTL:preferredSizes:] ()
#10 0x00000001837cf89c in -[_UICollectionLayoutItemSolver solveForContainer:layoutAxis:traitCollection:maxFrameCount:layoutRTL:] ()
#11 0x00000001837df388 in -[_UICollectionLayoutSectionFixedSolver _solve] ()
#12 0x00000001837bb1a0 in -[_UICollectionCompositionalLayoutSolver _solveWithSectionLayouts:preferredSizesDict:dataSourceSnapshot:update:] ()
#13 0x00000001837bac24 in -[_UICollectionCompositionalLayoutSolver _solve] ()
#14 0x00000001837b5944 in -[_UICollectionCompositionalLayoutSolver resolveForContainerChange:] ()
#15 0x00000001837acf68 in -[UICollectionViewCompositionalLayout _boundsChangeResolve] ()
#16 0x00000001837aaaec in -[UICollectionViewCompositionalLayout invalidateLayoutWithContext:] ()
#17 0x0000000183832f00 in -[UICollectionView _invalidateLayoutForUpdatedLayoutMarginsIfNeeded] ()
#18 0x0000000183832dc8 in -[UICollectionView layoutMarginsDidChange] ()
#19 0x0000000184592374 in -[UIView _layoutMarginsDidChangeFromOldMargins:] ()
#20 0x0000000184592acc in -[UIView _updateInferredLayoutMarginsFromSuperview:] ()
#21 0x00000001845a50c4 in -[UIView(Geometry) setBounds:] ()
#22 0x0000000184533548 in -[UIScrollView setBounds:] ()
#23 0x0000000183832474 in -[UICollectionView setBounds:] ()
#24 0x00000001845a43b0 in -[UIView(Geometry) _applyISEngineLayoutValuesToBoundsOnly:] ()
#25 0x00000001845a4790 in -[UIView(Geometry) _resizeWithOldSuperviewSize:] ()
#26 0x00000001844c8184 in -[UIScrollView(_UIOldConstraintBasedLayoutSupport) _resizeWithOldSuperviewSize:] ()
#27 0x00000001845a3c8c in __46-[UIView(Geometry) resizeSubviewsWithOldSize:]_block_invoke ()
#28 0x00000001817cd1d0 in __NSARRAY_IS_CALLING_OUT_TO_A_BLOCK__ ()
#29 0x0000000181731478 in -[__NSArrayM enumerateObjectsWithOptions:usingBlock:] ()
#30 0x00000001845a3be8 in -[UIView(Geometry) resizeSubviewsWithOldSize:] ()
#31 0x00000001844d619c in -[UIView(AdditionalLayoutSupport) _is_layout] ()
#32 0x00000001845ab8ac in -[UIView _updateConstraintsAsNecessaryAndApplyLayoutFromEngine] ()
#33 0x0000000183cff4e8 in -[_UIDatePickerCalendarDateView layoutSubviews] ()
#34 0x00000001845be398 in -[UIView(CALayerDelegate) layoutSublayersOfLayer:] ()
#35 0x0000000184ac3df4 in -[CALayer layoutSublayers] ()
#36 0x0000000184aca398 in CA::Layer::layout_if_needed(CA::Transaction*) ()
#37 0x0000000184ad56e8 in CA::Layer::layout_and_display_if_needed(CA::Transaction*) ()
#38 0x0000000184a20d7c in CA::Context::commit_transaction(CA::Transaction*, double, double*) ()
#39 0x0000000184a4af40 in CA::Transaction::commit() ()
#40 0x0000000184a4c1f0 in CA::Transaction::observer_callback(__CFRunLoopObserver*, unsigned long, void*) ()
#41 0x00000001817c887c in __CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION__ ()
#42 0x00000001817c2f50 in __CFRunLoopDoObservers ()
#43 0x00000001817c3498 in __CFRunLoopRun ()
#44 0x00000001817c2ba0 in CFRunLoopRunSpecific ()
#45 0x000000019852b598 in GSEventRunModal ()
#46 0x00000001840b42f4 in -[UIApplication _run] ()
#47 0x00000001840b9874 in UIApplicationMain ()
#48 0x000000010325aef0 in main at /Users/ashishn/Documents/Developer/XCode Projects/YOVL-Xcode/Source/AppDelegate.swift:99
#49 0x00000001814a1568 in start ()

Generally sender should be set to `UITapGestureRecognizer`, not `Any`, i.e. `func startDateLabelTapped(_ sender: UITapGestureRecognizer)`. I don't know if it can cause such crash though — timbre timbre, Mar 21 '21 at 18:49
I am not using sender object in the method so it may not affect. I have checked with print statement after isHidden that the method is called. No app specific code is executed after it and The memory jumps executing some internal code. I can’t catch using breakpoint also as app crash due to memory. Added two screenshots from Instruments. — ashishn, Mar 22 '21 at 09:08

CSmith · Accepted Answer · 2021-03-22T11:35:08.937

You are animating a hidden view, and also inserting an async dispatch inside the animation block which changes the hidden state ... this seems wrong to me.

Try this code, which animates the alpha property and uses completion block to turn on hidden property when hiding.

@objc private func startDateLabelTapped(_ sender: Any) 
{
    if self.startDatePicker.isHidden 
    {
       // un-hide it
       self.startDatePicker.isHidden = false
       UIView.animate(withDuration: 0.3, delay: 0, options: [.transitionFlipFromLeft]) 
       {
            // animate alpha to make it visible
            self.startDatePicker.alpha = 1.0
       } completion: { (success: Bool) in
       }
    }
    else
    {
        UIView.animate(withDuration: 0.3, delay: 0, options: [.transitionFlipFromLeft]) 
        {
            // animate alpha to make it invisible
            self.startDatePicker.alpha = 0
        } completion: { (success: Bool) in
            // then hide it once animation is complete
            self.startDatePicker.isHidden = true
        }
    }
}

Be aware that this combines the alpha animation with the flip transition ... in other words it will fade in/out during the flip. If you want these to be discrete, flip then fade in/out, you can achieve this by chaining animations. Use the UIView.animation completion block to start the 2nd animation.

This didn't help. I created a sample project mocking similar scenario ie VC with collection view opening VC with hide/show. Strangely my app works fine on iPhone 8 simulator but fails only on device !! I save added stack trace. i don't know why collection view related code is executed when i hide a control on another view. — ashishn, Mar 25 '21 at 18:01

score 0 · Answer 2 · answered Apr 04 '21 at 15:34

Taking hint from this answer, i embedded the UIDatePicker in UIView and it solved the issue. The issue reported on that thread wasn't same as what i was facing so hope this solution helps similar issues in feature.

I changed method to as below to adde hiding and showing embedding view.

@objc private func startDateSelectionLabelTapped(_ sender: Any) {
        
        if self.startDatePicker.isHidden {

            // un-hide it
            self.startDatePicker.isHidden = false
            self.startDatePickerembeddingView.isHidden = false

            UIView.animate(withDuration: 0.5, delay: 0, options: [.transitionFlipFromTop]) {

                // animate alpha to make it visible
                self.startDatePicker.alpha = 1.0
                
            } //end of UIView.animate
            
        } else {

            UIView.animate(withDuration: 0.5, delay: 0, options: [.transitionFlipFromBottom]) {

                // animate alpha to make it invisible
                self.startDatePicker.alpha = 0
                self.startDatePicker.isHidden = true
                self.startDatePickerembeddingView.isHidden = true

            } //end of UIView.animate

        }
    }

App crashes with low memory only on iPhone 8 iOS 14.4.1

2 Answers2

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