Scroll to bottom when keyboard appears causing crash - ios

Question

I want to scroll my tableview to bottom when keyboard appears. But i am getting lot of crash reports from my users.
My code:
func keyboardWillShow(_ notification: Foundation.Notification) {
var info = notification.userInfo!
let keyboardFrame: CGRect = (info[UIKeyboardFrameEndUserInfoKey] as! NSValue).cgRectValue
self.view.layoutIfNeeded()
UIView.animate(withDuration: 0.2, animations: {
self.bottomCons.constant = keyboardFrame.size.height
self.view.layoutIfNeeded()
})
let numberOfRows = tableView.numberOfRows(inSection: 0)
if numberOfRows != 0 {
do {
try tableView.scrollToRow(at: IndexPath(row: numberOfRows-1, section: 0), at: .bottom, animated: false)
}catch {
print("error")
}
}
}
Crash log:
Fatal Exception: NSRangeException
0 CoreFoundation 0x18f3bafe0 __exceptionPreprocess
1 libobjc.A.dylib 0x18de1c538 objc_exception_throw
2 CoreFoundation 0x18f299200 -[__NSArrayM removeObjectAtIndex:]
3 UIKit 0x195826f90 -[UITableView _existingCellForRowAtIndexPath:]
4 UIKit 0x195836a50 -[UITableView _heightForRowAtIndexPath:]
5 UIKit 0x1956291c0 -[UISectionRowData heightForRow:inSection:canGuess:]
6 UIKit 0x195628ebc -[UITableViewRowData rectForRow:inSection:heightCanBeGuessed:]
7 UIKit 0x19562c21c -[UITableView rectForRowAtIndexPath:]
8 UIKit 0x195704180 -[UITableView _contentOffsetForScrollingToRowAtIndexPath:atScrollPosition:]
9 UIKit 0x195703c84 -[UITableView scrollToRowAtIndexPath:atScrollPosition:animated:]
10 Ribony 0x1000a3044 ChatViewController.keyboardWillShow(Notification) -> () (ChatViewController.swift)
11 Ribony 0x1000a07d4 #objc ChatViewController.showConnectedLayout(Notification) -> ()
12 CoreFoundation 0x18f3555f4 __CFNOTIFICATIONCENTER_IS_CALLING_OUT_TO_AN_OBSERVER__
13 CoreFoundation 0x18f354d08 _CFXRegistrationPost
14 CoreFoundation 0x18f354a84 ___CFXNotificationPost_block_invoke
15 CoreFoundation 0x18f3c37a8 -[_CFXNotificationRegistrar find:object:observer:enumerator:]
16 CoreFoundation 0x18f29895c _CFXNotificationPost
17 Foundation 0x18fdaa930 -[NSNotificationCenter postNotificationName:object:userInfo:]
18 UIKit 0x195ed0190 -[UIInputWindowController postStartNotifications:withInfo:]
19 UIKit 0x195ed0edc __48-[UIInputWindowController viewDidLayoutSubviews]_block_invoke
20 UIKit 0x195ecdc04 -[UIInputWindowController performWithSafeTransitionFrames:]
21 UIKit 0x195ed098c -[UIInputWindowController viewDidLayoutSubviews]
22 UIKit 0x1954e90f4 -[UIView(CALayerDelegate) layoutSublayersOfLayer:]
23 QuartzCore 0x1926d9274 -[CALayer layoutSublayers]
24 QuartzCore 0x1926cdde8 CA::Layer::layout_if_needed(CA::Transaction*)
25 UIKit 0x1954fd814 -[UIView(Hierarchy) layoutBelowIfNeeded]
26 UIKit 0x195ecc4cc -[UIInputSetHostView layoutIfNeeded]
27 UIKit 0x195c79310 -[_UIRemoteKeyboards controllerDidLayoutSubviews:]
28 UIKit 0x195d49364 -[UICompatibilityInputViewController viewDidLayoutSubviews]
29 UIKit 0x1954e90f4 -[UIView(CALayerDelegate) layoutSublayersOfLayer:]
30 QuartzCore 0x1926d9274 -[CALayer layoutSublayers]
31 QuartzCore 0x1926cdde8 CA::Layer::layout_if_needed(CA::Transaction*)
32 UIKit 0x1954fd814 -[UIView(Hierarchy) layoutBelowIfNeeded]
33 UIKit 0x195ecc4cc -[UIInputSetHostView layoutIfNeeded]
34 UIKit 0x195ed4da0 -[UIInputWindowController _updateBackdropViews]
35 UIKit 0x195d4823c -[UICompatibilityInputViewController setInputMode:]
36 CoreFoundation 0x18f3555f4 __CFNOTIFICATIONCENTER_IS_CALLING_OUT_TO_AN_OBSERVER__
37 CoreFoundation 0x18f354d08 _CFXRegistrationPost
38 CoreFoundation 0x18f354a84 ___CFXNotificationPost_block_invoke
39 CoreFoundation 0x18f3c37a8 -[_CFXNotificationRegistrar find:object:observer:enumerator:]
40 CoreFoundation 0x18f29895c _CFXNotificationPost
41 Foundation 0x18fdaa930 -[NSNotificationCenter postNotificationName:object:userInfo:]
42 UIKit 0x195908be4 -[UIKeyboardImpl setKeyboardInputMode:userInitiated:updateIndicator:executionContext:]
43 UIKit 0x19590a388 -[UIKeyboardImpl setInputModeToNextInPreferredListWithExecutionContext:]
44 UIKit 0x1956aed88 -[UIKeyboardLayoutStar completeSendStringActionForTouchUp:withActions:timestamp:interval:didLongPress:prevActions:executionContext:]
45 UIKit 0x1956a1f18 -[UIKeyboardLayoutStar completeRetestForTouchUp:timestamp:interval:executionContext:]
46 UIKit 0x19592bbb8 __45-[UIKeyboardLayout touchUpTaskForTouchState:]_block_invoke
47 UIKit 0x195515e0c -[UIKeyboardTaskQueue continueExecutionOnMainThread]
48 UIKit 0x19592b868 -[UIKeyboardLayout _touchEndedProcessingForTouches:]
49 UIKit 0x195520390 -[UIWindow _sendTouchesForEvent:]
50 UIKit 0x19551b728 -[UIWindow sendEvent:]
51 UIKit 0x1954ec33c -[UIApplication sendEvent:]
52 UIKit 0x195ce6014 __dispatchPreprocessedEventFromEventQueue
53 UIKit 0x195ce0770 __handleEventQueue
54 UIKit 0x195ce0b9c __handleHIDEventFetcherDrain
55 CoreFoundation 0x18f36942c __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__
56 CoreFoundation 0x18f368d9c __CFRunLoopDoSources0
57 CoreFoundation 0x18f3669a8 __CFRunLoopRun
58 CoreFoundation 0x18f296da4 CFRunLoopRunSpecific
59 GraphicsServices 0x190d00074 GSEventRunModal
60 UIKit 0x195551058 UIApplicationMain
61 Ribony 0x10003f11c main (AppDelegate.swift:15)
62 libdyld.dylib 0x18e2a559c start
How can i resolve this issue?

Answer 1

I am convinced problem lays here
UIView.animate(withDuration: 0.2, animations: {
self.bottomCons.constant = keyboardFrame.size.height
self.view.layoutIfNeeded()
})
...
try tableView.scrollToRow(at: IndexPath(row: numberOfRows-1, section: 0), at: .bottom, animated: false)
You are reloading layout and trying to scroll in the very same moment, you should scroll afterwards or before. Might be I am not right, but this is usually the problem.