Setting UIButton background image stops animation - ios

Question

I try to set the background image in animation completion and basically it prevents the animation to happen.
This is the code for animation:
[UIView animateWithDuration: 0.5f animations: ^
{
//[buttonPanel setBackgroundImage: [UIImage imageNamed: imageName] forState: UIControlStateNormal];
CGFloat yOrigin = buttonFrame.origin.y - (self.bounds.size.height - buttonFrame.size.height);
yOrigin -= buttonFrame.size.height;
buttonPanel.frame = CGRectMake(buttonFrame.origin.x, yOrigin, buttonFrame.size.width, buttonFrame.size.height);
}
completion: ^(BOOL finished)
{
[UIView animateWithDuration: 0.5f animations:^
{
[buttonPanel setBackgroundImage: [UIImage imageNamed: imageName] forState: UIControlStateNormal];
[self setAlpha: 1.0f];
}];
}];
If I remove the setBackgroundImage: message it just animating to new frame position correctly. Why?
Thank you.

Answer 1

OK, new answer! Your comment gave me the clue I needed. You said:
Makes the button to return to initial frame for a reason. basically any operation, like calling a modal UIViewController from this UIViewController sets the button to initial Fram position
Right. Because showing a modal controller and then dismissing it causes your view to appear, and causes layout to happen. You must be using Auto Layout! Auto Layout would cause this to happen. So the problem here is that you don't understand how to change the position/size of a view (in animation or any other time) when using Auto Layout.
The rule is simple. He who lives by the constraint dies by the constraint. If you are using Auto Layout, you must not change the frame of anything. You must make all positional / size adjustments by changing a constraint.
The wonderful thing is that this is usually much easier and simpler than changing the frame! You don't have to fetch the frame, change it, and assign the frame; instead, you can usually just change a constraint's constant directly.
In this example, I animate the shrinkage of a UITextView so that the whole UITextView will be visible when the keyboard rises from the bottom of the screen (iPhone):
[UIView animateWithDuration:duration.floatValue
animations:
^{
self.bottomConstraint.constant = -r.size.height;
[self.view layoutIfNeeded];
} completion:nil];
That is how to animate a constraint: as you change the constant, you must also call layoutIfNeeded to get new layout at each instant of the animation.
So, I'm not saying that you are wrong not to use Auto Layout. It is "opt-in"; you can start using when you want to, you can use it in some nibs and not others, etc etc. But it is much more powerful than the old way of doing layout, and in many ways it leads to simpler code - once you know how to use it.

Answer 2

backgroundImage is not an animatable property so why are you setting it inside an animation block? Try setting it before all the animations. Just a guess, but worth trying.
EDIT: I just tried this:
[UIView animateWithDuration:0.4 animations:^{
CGRect r = self.otherButton.frame;
r.origin.y += 100;
self.otherButton.frame = r;
[self.otherButton setBackgroundImage:[UIImage imageNamed:#"car.jpg"]
forState:UIControlStateNormal];
}];
It worked fine. So I'm not able to reproduce your issue. Is there something else going on in your code that you aren't telling us about? In other words, try reducing it to a simpler case that works, and then build it back up and that way you'll discover the point at which things go wrong.

Answer 3

OK,
I have found this crazy issue, I had a UIViewController, Use Autolayout check and it was messing up all my animations.
Even if you have a UIViewController checked Use Autolayout it messes up all the controllers, maybe because I don't use UINavigationController, and
the segues are modal.
This was.