How to know if view is being animated? - ios

Question

Is there a way to know if my custom implementation of setFrame: (or an other setter of an animatable property) is being called from an animation block i.e. it will be animated or just set directly?
Example:
- (void)setFrame:(CGRect)newFrame {
[super setFrame:newFrame];
BOOL willBeAnimated = ?????
if (willBeAnimated) {
// do something
} else {
// do something else
}
}
In the above setter willBeAnimated should be YES it is called like this:
- (void)someMethod {
[UIView animateWithDuration:0.2
animations:^{view.frame = someRect;}
completion:nil];
}
and NO in this case:
- (void)someMethod {
view.frame = someRect;
}
someMethod here is a private method inside UIKit that I can't access or change, so I have to somehow determine this from the "outside".

Answer 1

You should be able to check the animationKeys of the layer of your UIView subclass right after changing the frame to see if it is being animated.
- (void)setFrame:(CGRect)newFrame {
[super setFrame:newFrame];
BOOL willBeAnimated = [super.layer animationForKey:#"position"] ? YES : NO;
if (willBeAnimated) {
// do something
} else {
// do something else
}
}
You can also to check if there are any animations by using animationsKeys which in this case would just return position.
In addition, if you want to force a change to not be animated you can use performWithoutAnimation:
[UIView performWithoutAnimation:^{
[super setFrame:newFrame];
}];
EDIT
Another tidbit I found by testing is that you can actually stop the animation if it is already in progress and instead making the change instantly by removing the animation from the layer and then using the above method instead.
- (void)setFrame:(CGRect)newFrame {
[super setFrame:newFrame];
BOOL willBeAnimated = [super.layer animationForKey:#"position"] ? YES : NO;
BOOL shouldBeAnimated = // decide if you want to cancel the animation
if (willBeAnimated && !shouldBeAnimated) {
[super removeAnimationForKey:#"position"];
[UIView performWithoutAnimation:^{
[super setFrame:newFrame];
}];
} else {
// do something else
}
}