Animating only the image in UIBarButtonItem

Question

Ive seen this effect in 2 apps and I REALLY want to find how to do it.

The animation is in a UIBarButtonItem, and is only to the image. The image is a + symbol, and

Answer 1

I wanted to keep the expanded tapping size that the native UIBarButtonItem view provides (such as -initWithBarButtonSystemItem:target:action: versus -initWithCustomView:).

Here's a basic implementation of my code.

- (void)setup {
    self.navigationItem.rightBarButtonItem = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemAdd target:self action:@selector(navigationBarRightAction)];
}

- (void)navigationBarRightAction {
    UIView *itemView = [self.navigationItem.rightBarButtonItem performSelector:@selector(view)];
    UIImageView *imageView = [itemView.subviews firstObject];

    if (self.shouldRotate) {
        imageView.contentMode = UIViewContentModeCenter;
        imageView.autoresizingMask = UIViewAutoresizingNone;
        imageView.clipsToBounds = NO;
        imageView.transform = CGAffineTransformMakeRotation(M_PI_4);

    } else {
        imageView.transform = CGAffineTransformIdentity;
    }
}