Core Animation Warning: "uncommitted CATransaction" - iphone

Question

I am getting the following warning with Device only:
CoreAnimation: warning, deleted thread with uncommitted CATransaction; created by:
0 QuartzCore 0x3763c65d <redacted> + 220
1 QuartzCore 0x3763c541 <redacted> + 224
2 QuartzCore 0x3763fe2f <redacted> + 30
3 QuartzCore 0x3763b9bf <redacted> + 318
4 QuartzCore 0x3763b87b <redacted> + 50
5 QuartzCore 0x3763b80b <redacted> + 538
6 MyApp 0x000df597 -[CommonClass orangeGradient:] + 382
7 MyApp 0x000f70e1 -[HomeViewController updateStatusBar] + 1700
8 MyApp 0x000f61bd -[HomeViewController statusRecieved] + 224
9 MyApp 0x000cd323 -[CommonClass statusReceivedFromServer] + 142
10 MyApp 0x000d833d -[CommonClass accountStatus] + 7416
11 Foundation 0x35a3767d <redacted> + 972
12 libsystem_c.dylib 0x35c9a311 <redacted> + 308
13 libsystem_c.dylib 0x35c9a1d8 thread_start + 8
My Method that is on top of the stack is as follows:
- (void)orangeGradient: (UILabel *)fillLabel {
#synchronized([CommonClass class]) {
CAGradientLayer * gradientLayer = [CAGradientLayer layer];
gradientLayer.frame = fillLabel.bounds;
gradientLayer.colors = [NSArray arrayWithObjects:(id)[UIColorFromRGB(0xfbb250) CGColor],(id)[UIColorFromRGB(0xf47c2a) CGColor], nil];
[fillLabel.layer addSublayer:gradientLayer];
}
}
Any idea on why is this coming, and how I can fix this?

Answer 1

It looks like orangeGradient: is called from a background thread. Core Animation groups all changes into CATransactions. Usually this is done automatically from the run loop. On background threads there is (usually) no run loop, so you have to create the transaction yourself:
- (void)orangeGradient: (UILabel *)fillLabel {
#synchronized([CommonClass class]) {
[CATransaction begin];
CAGradientLayer * gradientLayer = [CAGradientLayer layer];
gradientLayer.frame = fillLabel.bounds;
gradientLayer.colors = [NSArray arrayWithObjects:(id)[UIColorFromRGB(0xfbb250) CGColor],(id)[UIColorFromRGB(0xf47c2a) CGColor], nil];
[fillLabel.layer addSublayer:gradientLayer];
[CATransaction commit];
}
}
There's another issue: UIKit is not thread safe. You can't call bounds on a UILabel on a background thread.

Answer 2

Check anywhere in your code there is an uncommitted CATransaction. You will need to perform this operation following way;
[CATransaction begin];
[CATransaction setDisableActions:YES];
[commonClassObject orangeGradient:lblFill];
[CATransaction commit];
[EDIT]
Basically this problem happens when NSOperation completes before CoreAnimation is done performing. There must be some relation between these two class in somewhere in your code you need to figure that out.

Answer 3

I'll just add that I had the same problem with initWithFrame from a background threads.
Seems that since iOS 7 and upwards, some calls to UIKit must be done under the main thread, and cannot be called from a background thread.
Also note that after several warnings like this, my app stopped responding completely. So better not ignore such warning.