Toolbar button selector not fired with message in console: <Error>: CGContextSaveGState: invalid context

Question

I am adding UIToolbar programatically with the below code. It should handle basic image editing, but when I tap any button on the toolbar, I get this error message instead, and the selector is not called. The viewController is embeded in UINavigationController and has UIScrollView with UIImageView.

I have found here that the error might be ignored in some cases as it is a bug in iOS, however in my situation my selector is also not called along with this message. I have also found someone get this error with zero sized CGContext and I do some image capturing with CGContext, but it is working fine and it is not related to toolbar buttons and selectors. Any suggestions?

<Error>: CGContextSaveGState: invalid context 0x0. This is a serious error.
This application, or a library it uses, is using an invalid context  and is
thereby contributing to an overall degradation of system stability and
reliability. This notice is a courtesy: please fix this problem. It will
become a fatal error in an upcoming update.

Code:

- (void)addBasicToolbar
{
    // create toolbar
    UIToolbar *basicToolbar = [[UIToolbar alloc] init];
    basicToolbar.barStyle = UIBarStyleBlack;
    basicToolbar.translucent = NO;
    basicToolbar.translatesAutoresizingMaskIntoConstraints = NO;
    [self.view addSubview:basicToolbar];

    // add constraints
    NSDictionary *metrics = @{@"barHeight":@44.0};
    [self.view addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"|[basicToolbar]|" options:0 metrics:nil views:NSDictionaryOfVariableBindings(basicToolbar)]];
    [self.view addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:[basicToolbar(==barHeight)]|" options:0 metrics:metrics views:NSDictionaryOfVariableBindings(basicToolbar)]];

    // add bar buttons
    UIBarButtonItem *rotateLeft = [[UIBarButtonItem alloc] initWithTitle:@"Rotate left" style:UIBarButtonItemStylePlain target:self action:@selector(rotateLeft)];
    UIBarButtonItem *rotateRight = [[UIBarButtonItem alloc] initWithTitle:@"Rotate right" style:UIBarButtonItemStylePlain target:self action:@selector(rotateRight)];
    UIBarButtonItem *resetButton = [[UIBarButtonItem alloc] initWithTitle:@"Revert to original" style:UIBarButtonItemStylePlain target:self action:@selector(resetToOriginal)];
    UIBarButtonItem *markupButton = [[UIBarButtonItem alloc] initWithTitle:@"Add markup" style:UIBarButtonItemStylePlain target:self action:@selector(addMarkup)];
    UIBarButtonItem *flexibleSpace = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemFlexibleSpace target:nil action:nil];

    basicToolbar.items = @[resetButton, flexibleSpace, rotateLeft, rotateRight, flexibleSpace, markupButton];
}

- (void)rotateLeft
{
    NSLog(@"rotate left called"); // but is actually not called
}

Answer 1

I found the issue on the end. I have tap gesture recognizer which cancelled touch events and they never reached the tabbar. Still have no idea why the CGContext error appeared.