CODEWITHSUNDEEP
iosobjective-cuitableviewvoiceover
Arie Litovsky
Arie Litovsky

Reputation: 4983

Switching between multiple UITableView with VoiceOver causes crash

I have a UIViewController with the following view hierarchy:

    UIView (root of UIViewController)
      |__________
      |          |
UITableView(A)  UIView (overlay view)
            ____|_______
           |            |
       UITableView(B)  UITableView(C)

None of the UITableViews are shown simultaneously – I simply switch between them for various reasons: one is for normal items, one is used for searching results, etc.

I'm getting this crash, somewhat consistently, by turning on VoiceOver, causing UITableView B to appear, dismissing it, and then navigating through accessibility items in UITableView A.

Here's the call stack:

Thread : Crashed: com.apple.main-thread
0  libobjc.A.dylib                0x00000001954a7bd0 objc_msgSend + 16
1  UIKit                          0x000000018317ea68 -[UITableViewCellAccessibility _accessibilityReuseChildren:forMockParent:] + 496
2  UIKit                          0x000000018318f28c -[UITableViewCellAccessibilityElement tableViewCell] + 260
3  UIKit                          0x000000018318fcac -[UITableViewCellAccessibilityElement isAccessibilityElement] + 24
4  UIAccessibility                0x0000000191c2c030 _appendChildrenToArrayStartingAtIndexWithChildren + 352
5  UIAccessibility                0x0000000191c2bd04 _addAXElementsToArrayFromObject + 1620
6  UIAccessibility                0x0000000191c2b680 _appendVendedAXElementsFromUIElements + 288
7  UIAccessibility                0x0000000191c2b53c _createAXUIElementsFromUIElements + 160
8  UIAccessibility                0x0000000191c2a3cc _copyParameterizedAttributeValueCallback + 208
9  AXRuntime                      0x000000018a5f4a30 _AXXMIGCopyParameterizedAttributeValue + 256
10 AXRuntime                      0x000000018a5f0850 _XCopyParameterizedAttributeValue + 412
11 AXRuntime                      0x000000018a5fbbc0 mshMIGPerform + 272
12 CoreFoundation                 0x0000000184cf6200 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE1_PERFORM_FUNCTION__ + 56
13 CoreFoundation                 0x0000000184cf6160 __CFRunLoopDoSource1 + 436
14 CoreFoundation                 0x0000000184cf40e0 __CFRunLoopRun + 1640
15 CoreFoundation                 0x0000000184c210a4 CFRunLoopRunSpecific + 396
16 GraphicsServices               0x000000018ddc35a4 GSEventRunModal + 168
17 UIKit                          0x00000001895563c0 UIApplicationMain + 1488
18 Stack Exchange                 0x000000010018dbe4 main (main.m:16)
19 libdyld.dylib                  0x0000000195b02a08 start + 4

The crashing error is:

[UITableTextAccessibilityElement accessibilityContainer] message sent to deallocated instance

I'm running on iOS 8.1.2.

Clearly, this has something to do with VoiceOver, or rather, the way UIAccessibility is navigating through its accessibility elements, trying to access a deallocated object. I've tried posting accessibility notifications such as UIAccessibilityScreenChangedNotification and UIAccessibilityLayoutChangedNotification after hiding and showing the UITableViews to let the accessibility know that the screen has changed, but haven't had any luck.

My UITableViews A and C also have some extra subviews, used as refresh/load more controls, but even removing these isn't helping.

Update: I am also getting these warnings when using VoiceOver to tap on a UITextField which is a subview of UITableView(a) headerView property:

**** Accessibility: Could not find a valid index for <SESearchBar: 0x16a03150; frame = (0 0; 320 44); text = ''; layer = <CALayer: 0x16a02fc0>> in -[UITableView indexOfAccessibilityElement:]
|warning| **** Accessibility: Could not find where <SESearchBar: 0x16a03150; frame = (0 0; 320 44); text = ''; layer = <CALayer: 0x16a02fc0>> starts. Was its parent [<UITableView: 0x16208a00; frame = (0 0; 320 504); clipsToBounds = YES; autoresize = RM+BM; gestureRecognizers = <NSArray: 0x16b4a8c0>; layer = <CALayer: 0x16b49750>; contentOffset: {0, 0}; contentSize: {320, 1800}>] set correctly or did it disappear?

Upvotes: 3

Views: 777

Answers (1)

Mikrohard
Mikrohard

Reputation: 211

I had a similar issue in my project. After a few hours of debugging I found what the issue has been. It turns out that VoiceOver crashed due to some empty (empty as in without any labels/images/etc.) table view cells (I use empty cells as as additional spacing separators around the selected cell in a specific section). After I removed the accessibility elements in those cells the crashes also disappeared... maybe this helps in your case too.

- (NSInteger)accessibilityElementCount {
    return 0;
}

- (NSArray *)accessibilityElements {
    return nil;
}

Upvotes: 1

Related Questions