Custom table cells and NSAccessibilityExceptions
Custom table cells and NSAccessibilityExceptions
- Subject: Custom table cells and NSAccessibilityExceptions
- From: Mickey Roberson <email@hidden>
- Date: Mon, 10 May 2010 17:57:22 -0400
| I have implemented custom table cells (subclass of NSTextFieldCell) in my application (a Twitter client). Each cell represents a tweet including things like name, date, tweet text, etc. Within my cell subclass I have the following code:
- (NSArray *)accessibilityAttributeNames {
if(validAXAttributes == nil) {
validAXAttributes = [[NSArray alloc] initWithObjects:NSAccessibilityRoleAttribute,
NSAccessibilityRoleDescriptionAttribute,
NSAccessibilityHelpAttribute,
NSAccessibilityFocusedAttribute,
NSAccessibilityParentAttribute,
NSAccessibilityChildrenAttribute,
NSAccessibilityWindowAttribute,
NSAccessibilityPositionAttribute,
NSAccessibilitySizeAttribute,
NSAccessibilityEnabledAttribute,
NSAccessibilityValueAttribute, nil];
}
return validAXAttributes;
}
- (id)accessibilityAttributeValue:(NSString *)attribute
{
if([attribute isEqualToString:NSAccessibilityRoleAttribute]) //AXRole
return NSAccessibilityStaticTextRole;
if([attribute isEqualToString:NSAccessibilityRoleDescriptionAttribute]) //AXRoleDescription
return @"Timeline Tweet";
if([attribute isEqualToString:NSAccessibilityHelpAttribute]) //AXHelp
return @"Timeline Tweet";
if([attribute isEqualToString:NSAccessibilityValueAttribute]) { //AXValue
SRXTweetObject* tweet = (SRXTweetObject*)[self objectValue];
NSMutableString* readableString = [NSMutableString stringWithFormat:@"%@: %@", [tweet.user displayName], tweet.text];
//Removed for brevity...
return readableString;
}
return [super accessibilityAttributeValue:attribute];
}
For the most part this behaves correctly except that it occasionally reads the Accessibility Content twice. While looking into this in gdb I noticed that multiple NSAccessibilityExceptions are being thrown when I turn VO on with a tweet as main focus.
2010-05-10 17:39:43.954 Syrinx[85907:a0f] NSExceptionHandler has recorded the following exception:
NSAccessibilityException -- Attempt to observe "AXTextInputMarkingSessionBegan" on non-observable element: <NSTableViewCellProxy: 0x11d4ebbf0> col:0 row:33 real element:<SRXTableCell: 0x11d51e5a0>
Stack trace: 0x7fff81c18a2c 0x7fff827510f3 0x7fff82ed19b9 0x7fff86485c45 0x7fff864839f5 0x7fff8618900b 0x7fff86192f6c 0x7fff8616f541 0x7fff82e16201 0x7fff82e148df 0x7fff85349ada 0x7fff853498df 0x7fff85349798 0x7fff86235a2a 0x7fff86235379 0x7fff861fb05b 0x7fff861f3d7c 0x100001365 0x100001314 0x1
(gdb) continue
(gdb) continue
2010-05-10 17:39:44.641 Syrinx[85907:a0f] NSExceptionHandler has recorded the following exception:
NSAccessibilityException -- Attempt to observe "AXCreated" on non-observable element: <NSTableViewCellProxy: 0x11e673ac0> col:0 row:33 real element:<SRXTableCell: 0x11d51e5a0>
Stack trace: 0x7fff81c18a2c 0x7fff827510f3 0x7fff82ed19b9 0x7fff86485c45 0x7fff864839f5 0x7fff8618900b 0x7fff86192f6c 0x7fff8616f541 0x7fff82e16201 0x7fff82e148df 0x7fff85349ada 0x7fff853498df 0x7fff85349798 0x7fff86235a2a 0x7fff86235379 0x7fff861fb05b 0x7fff861f3d7c 0x100001365 0x100001314 0x1
What am I doing wrong that is causing these exceptions, and how do I fix them?
_______________________ Mickey Roberson
MRR Software
|
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