how to animate both the frame of an UIView and the frame of one of its sublayers? - objective-c

Question

What I have:
I have a UIView (named pView) which has as sublayer a CAGradientLayer. Practically is this:
ViewController -> View ->pView -> CAGradientLayer
This is the code that creates all this:
#implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
UITestView * pView = nil;
UIColor * scolor = nil, *ecolor = nil;
self.view.backgroundColor = [UIColor yellowColor];
pView = [[UITestView alloc] initWithFrame: CGRectMake(self.view.frame.origin.x, 100.0, self.view.frame.size.width, 100.0)];
scolor = [UIColor colorWithRed:(14/255.0) green: (238/255.0) blue:(123/255.0) alpha:1];
ecolor = [UIColor colorWithRed:(6/255.0) green: (216/255.0) blue:(69/255.0) alpha:1];
// creating the gradient layer
CAGradientLayer * layer = [[CAGradientLayer alloc] init];
layer.frame = self.bounds;
layer.colors = #[(id)scolor.CGColor,(id)ecolor.CGColor];
[pView.layer insertSublayer:layer atIndex:0];
// creating a tapGestureRecognizer
[pView addGestureRecognizer:[[UITapGestureRecognizer alloc] initWithTarget:self action:#selector(handleTapInViews:)]];
[self.view addSubview:pView];
touched = NO;
}
....
#end
What I'm trying to do
Once a tap gesture is detected over pView I want to increase the height of pView by 100.0 but animatedly. If pView was previously touched (that is, its height was already increased by 100.0) I want to decrease the height of pView by 100.0 (that is, returning it to its original size);
What I already know
I know that since I want to change the frame of pView I must change also the frame (or bounds) of the CAGradientLayer attached to pView. Since I want to animate these changes, I want these animations occurs at the same time and have the same duration.
I know that the frame (or bounds) of a layer is only animatable inside an animation block.
What I do:
This is the option I've test:
- (void) handleTapInViews: (nonnull UITapGestureRecognizer *) sender {
pView = sender.view;
if (touched) {
[UIView animateWithDuration:0.4 animations:^{
pView.frame = CGRectMake(pView.frame.origin.x, pView.frame.origin.y, pView.frame.size.width, pView.frame.size.height - 100.0);
pView.layer.sublayers[0].frame = pView.bounds;
[self.view setNeedsLayout];
} completion:^(BOOL finished) {
touched = NO;
}];
}
else {
[UIView animateWithDuration:0.4 animations:^{
pView.frame = CGRectMake(pView.frame.origin.x, pView.frame.origin.y, pView.frame.size.width, pView.frame.size.height + 100.0);
pView.layer.sublayers[0].frame = pView.bounds;
[self.view setNeedsLayout];
} completion:^(BOOL finished) {
touched = YES;
}];
}
}
This option actually works (that is, both the frame of pView and the frame of the layer change animatedly) but they are not synchronised; that is, the changes in the frame of the layer are slightly (but perceptible) more faster than the changes in the frame of pView. This effect is more evident when the height of pView is decreased.
I 've also read about CABasicAnimation and CAAnimationGroup, in order to animate both the bounds and position of the layer. In this case also the animation of the layer is bit faster than the animation of the view (it is perceptible and it is not a matter of seconds in case anyone ask about setting duration or whatever) and also in this case, after the animation the bound of the layer return to its original size which is not the desired effect. I already know this last matter can be fixed assigned the new values to the layer at the end of the animation but I certainty do not know where in my code put that.
Most of what i've read regarding this other option is from these links:
link1
link2
link3
link4
In any case, does anybody please knows how can I fix this?? thanks in advance.

Answer 1

Well I ended setting the backgroundColor of Pview as ecolor = [UIColor colorWithRed:(6/255.0) green: (216/255.0) blue:(69/255.0) alpha:1. This way, the effect I commented about the animation of the layer been faster than the animation of the view is not noticeable now. I think maybe this is not the proper answer but it suit me.