I have a UIImageView that when the user taps it, a border of 4 points toggles on and off. I'm trying to animate the border in and out as follows:
CABasicAnimation *widthAnimation = [CABasicAnimation animationWithKeyPath:#"borderWidth"];
widthAnimation.toValue = self.isSelected ? #4.0 : #0.0;
widthAnimation.duration = 0.1;
[self.imageView.layer addAnimation:widthAnimation forKey:#"borderWidth"];
Now, as I've learned from research and scouring SO, CABasicAnimation just changes the presentation layer, but not the actual model. I've also read that using fillMode and removedOnCompletion is bad practice, since it leads to inconsistencies between the model and what the user sees. So, I tried to change the model with the following line:
self.imageView.layer.borderWidth = self.isSelected ? 4.0 : 0.0;
The problem is, this line seems to set the property straight away, so by the time the animation kicks in, the border width is already at it's desired value. I've tried sticking this line at the beginning of the code, end, and everywhere in between, but to no success. I did manage to find a hacky solution: instead of setting the property, I passed the property setter to performSelector: withObject: afterDelay:, with the delay being the duration of the animation. This works most of the time, but sometimes the cycles don't quite match up, and the animation will run first, then it jumps back to the original state, then it snaps to the new state, presumably as a result of performSelector
So is there any way to smoothly animate a border without performSelector?
Any help is greatly appreciated.
Here is an example of CABasicAnimation I made a while ago :
-(void) animateProgressFrom:(CGFloat)fromValue to:(CGFloat)toValue
{
CABasicAnimation *animation = [CABasicAnimation animationWithKeyPath:#"opacity"];
animation.fromValue = #(fromValue);
animation.toValue = #(toValue);
animation.duration = ABS(toValue - fromValue)*3.0;
[self.layer addAnimation:animation forKey:#"opacity"];
[CATransaction begin];
[CATransaction setDisableActions:YES];
self.layer.opacity = toValue;
[CATransaction commit];
}
I think what you needed is the CATransaction at the end of the layer animation.
Related
I have an iOS app which is using a CABasicAnimation on repeat:
CABasicAnimation *fadeAnim = [CABasicAnimation animationWithKeyPath:#"opacity"];
fadeAnim.fromValue = [NSNumber numberWithFloat:1.0];
fadeAnim.toValue = [NSNumber numberWithFloat:0.2];
fadeAnim.duration = 1.0;
fadeAnim.autoreverses = YES;
fadeAnim.repeatCount = INFINITY;
[colourbutton.titleLabel.layer addAnimation:fadeAnim forKey:#"opacity"];
I have a button which when pressed is meant to stop the animation.
-(IBAction)stopAnim {
[colourbutton.titleLabel.layer removeAllAnimations];
}
It works fine but one thing I am noticing is that is stops the animation suddenly, it doesn't let the animation finish. So how can I get it to finish the current animation and then stop. (Or in other words how can I get it to removeAllAnimations....withAnimation?).
On a side note, do I need to include CoreAnimation framework for this to work. So far the animation is running and I havn't imported the CoreAnimation framework.
Thanks, Dan.
Just add another animation and after that remove the first one like this:
CABasicAnimation *endAnimation = [CABasicAnimation animationWithKeyPath:#"opacity"];
endAnimation.fromValue = #(((CALayer *)colourbutton.titleLabel.layer.presentationLayer).opacity);
endAnimation.toValue = #(1);
endAnimation.duration = 1.0;
[colourbutton.titleLabel.layer addAnimation:endAnimation forKey:#"end"];
[colourbutton.titleLabel.layer removeAnimationForKey:#"opacity"];
The key here is to use the presentation layer to get the current state. Don't forget to set the actual end state of the layer, because the animation will be removed on completion.
In NKorotov's answer, he uses the presentationLayer to find out where you are in the animation. That is the correct way to go.
You could go with this solution, although IMO you would also have to calculate the duration animation correctly (based on the duration of the original animation and on how far you are along the animation path currently).
If you find it "silly" to add a new animation, you could perhaps call removeAllAnimations using dispatch_after at the correct time.
I am using a CABasicAnimation to rotate a UIImageView 90 degrees clockwise, but I need to have it rotate a further 90 degrees later on from its position after the initial 90 degree rotation.
CABasicAnimation *animation = [CABasicAnimation animationWithKeyPath:#"transform.rotation.z"];
animation.duration = 10;
animation.additive = YES;
animation.removedOnCompletion = NO;
animation.fillMode = kCAFillModeForwards;
animation.fromValue = [NSNumber numberWithFloat:DEGREES_TO_RADIANS(0)];
animation.toValue = [NSNumber numberWithFloat:DEGREES_TO_RADIANS(90)];
[_myview.layer addAnimation:animation forKey:#"90rotation"];
Using the code above works initially, the image stays at a 90 degree angle. If I call this again to make it rotate a further 90 degrees the animation starts by jumping back to 0 and rotating 90 degrees, not 90 to 180 degrees.
I was under the impression that animation.additive = YES; would cause further animations to use the current state as a starting point.
Any ideas?
tl;dr: It is very easy to misuse removeOnCompletion = NO and most people don't realize the consequences of doing so. The proper solution is to change the model value "for real".
First of all: I'm not trying to judge or be mean to you. I see the same misunderstanding over and over and I can see why it happens. By explaining why things happen I hope that everyone who experience the same issues and sees this answer learn more about what their code is doing.
What went wrong
I was under the impression that animation.additive = YES; would cause further animations to use the current state as a starting point.
That is very true and it's exactly what happens. Computers are funny in that sense. They always to exactly what you tell them and not what you want them to do.
removeOnCompletion = NO can be a bitch
In your case the villain is this line of code:
animation.removedOnCompletion = NO;
It is often misused to keep the final value of the animation after the animation completes. The only problem is that it happens by not removing the animation from the view. Animations in Core Animation doesn't alter the underlying property that they are animating, they just animate it on screen. If you look at the actual value during the animation you will never see it change. Instead the animation works on what is called the presentation layer.
Normally when the animation completes it is removed from the layer and the presentation layer goes away and the model layer appears on screen again. However, when you keep the animation attached to the layer everything looks as it should on screen but you have introduced a difference between what the property says is the transform and how the layer appears to be rotated on screen.
When you configure the animation to be additive that means that the from and to values are added to the existing value, just as you said. The problem is that the value of that property is 0. You never change it, you just animate it. The next time you try and add that animation to the same layer the value still won't be changed but the animation is doing exactly what it was configured to do: "animate additively from the current value of the model".
The solution
Skip that line of code. The result is however that the rotation doesn't stick. The better way to make it stick is to change the model. Set the new end value of the rotation before animating the rotation so that the model looks as it should when the animation gets removed.
byValue is like magic
There is a very handy property (that I'm going to use) on CABasicAnimation that is called byValue that can be used to make relative animations. It can be combined with either toValue and fromValue to do many different kinds of animations. The different combinations are all specified in its documentation (under the section). The combination I'm going to use is:
byValue and toValue are non-nil. Interpolates between (toValue - byValue) and toValue.
Some actual code
With an explicit toValue of 0 the animation happens from "currentValue-byValue" to "current value". By changing the model first current value is the end value.
NSString *zRotationKeyPath = #"transform.rotation.z"; // The killer of typos
// Change the model to the new "end value" (key path can work like this but properties don't)
CGFloat currentAngle = [[_myview.layer valueForKeyPath:zRotationKeyPath] floatValue];
CGFloat angleToAdd = M_PI_2; // 90 deg = pi/2
[_myview.layer setValue:#(currentAngle+angleToAdd) forKeyPath:zRotationKeyPath];
CABasicAnimation *animation = [CABasicAnimation animationWithKeyPath:zRotationKeyPath];
animation.duration = 10;
// #( ) is fancy NSNumber literal syntax ...
animation.toValue = #(0.0); // model value was already changed. End at that value
animation.byValue = #(angleToAdd); // start from - this value (it's toValue - byValue (see above))
// Add the animation. Once it completed it will be removed and you will see the value
// of the model layer which happens to be the same value as the animation stopped at.
[_myview.layer addAnimation:animation forKey:#"90rotation"];
Small disclaimer:
I didn't run this code but am fairly certain that it runs as it should and that I didn't do any typos. Correct me if I did. The entire discussion is still valid.
pass incremental value of angle see my code
static int imgAngle=0;
- (void)doAnimation
{
CABasicAnimation *animation = [CABasicAnimation animationWithKeyPath:#"transform.rotation.z"];
animation.duration = 5;
animation.additive = YES;
animation.removedOnCompletion = NO;
animation.fillMode = kCAFillModeForwards;
animation.fromValue = [NSNumber numberWithFloat:DEGREES_TO_RADIANS(imgAngle)];
animation.toValue = [NSNumber numberWithFloat:DEGREES_TO_RADIANS(imgAngle+90)];
[self.imgView.layer addAnimation:animation forKey:#"90rotation"];
imgAngle+=90;
if (imgAngle>360) {
imgAngle = 0;
}
}
Above code is just for idea. Its not tested
I am trying to animate a CAEmitterLayer's emitterPosition like this:
CABasicAnimation *animation = [CABasicAnimation animationWithKeyPath:#"emitterPosition.x"] ;
animation.toValue = (id) toValue ;
animation.removedOnCompletion = NO ;
animation.duration = self.translationDuration ;
animation.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseInEaseOut] ;
animation.completion = ^(BOOL finished)
{
[self animateToOtherSide] ;
} ;
[_emitterLayer addAnimation:animation forKey:#"emitterPosition"] ;
CGPoint newEmitterPosition = CGPointMake(toValue.floatValue, self.bounds.size.height/2.0) ;
_emitterLayer.emitterPosition = newEmitterPosition ;
Note that animation.completion is declared in a category that just calls the corresponding CAAnimation delegate method.
The problem is that this doesn't animate at all and shows the emitter in its final position. I was under the impression that once you add the animation to the layer, you should change the actual model behind it to its final position so that when the animation completes the model is in its final state; i.e., to prevent the animation from "snapping back" to its original position.
I have tried placing the last two lines in the animation.completion block, and this does indeed animate as expected. However, when the animation finishes some particles are intermittently emitted at the emitter's original position. If you put the system under load (for example, scrolling a tableview while the animation is playing), this happens more often.
Another solution I was thinking about is to not move the emitterPosition at all but just move the CAEmitterLayer itself, although I haven't tried that yet.
Thanks in advance for any help you can provide.
Perhaps emitterPosition.x is not a valid key path for animation. Try using emitterPosition instead (and so you'll have to provide CGPoint values wrapped up in an NSValue).
I just tried this on my own machine and it works fine:
CABasicAnimation* ba = [CABasicAnimation animationWithKeyPath:#"emitterPosition"];
ba.fromValue = [NSValue valueWithCGPoint:CGPointMake(30,100)];
ba.toValue = [NSValue valueWithCGPoint:CGPointMake(200,100)];
ba.duration = 6;
ba.autoreverses = YES;
ba.repeatCount = HUGE_VALF;
[emit addAnimation:ba forKey:nil];
Other things to think about:
You can typically use nil as the key in addAnimation:forKey:, unless you're going to need to find this animation later (e.g. to remove it or override it in some way). The key path is the important thing.
Setting removedOnCompletion to NO is almost always wrong and is typically the last refuge of a scoundrel (i.e. due to not understanding how animation works).
If, as you say, setting _emitterLayer.emitterPosition = newEmitterPosition inside the completion block does animate, then when why are you using CABasicAnimation at all? Why not just call UIView animate... and set the emitterPosition in the animations block? If that works, it will kill two birds with one stone, moving the position and animating it too.
I am creating some animation on my application and the code below zooms out an object till it disappears. I can't figure out how to make the object to disappear and keep that way, ie. how to make the animation stay put after it finishes. Any gotchas on that? Cheers!
CABasicAnimation* zoomOut = [CABasicAnimation animationWithKeyPath:#"transform.scale"];
zoomOut.duration = 1;
zoomOut.toValue = [NSNumber numberWithFloat:0];
[draggedObject addAnimation:zoomOut forKey:nil];
I found it. It also needs the two methods below:
zoomOut.removedOnCompletion = NO;
zoomOut.fillMode = kCAFillModeForwards;
Ok so this happens because the animation doesn't actually change the underlying property, which is why it jumps back after the animation is complete.
Try adding this line before the line starting the animation -
zoomOut.removedOnCompletion = NO;
i'm rotating a CALayer using CABasicAnimation and works fine. The problem is, when I try to rotate the same layer, it returns back to its original position before it will rotate. My expected output is that, for the next rotation, it should start from where it has ended. Here's my code:
CABasicAnimation *animation = [CABasicAnimation animationWithKeyPath:#"transform.rotation"];
animation.fromValue = 0;
animation.toValue = [NSNumber numberWithFloat:3.0];
animation.duration = 3.0;
animation.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseInEaseOut];
animation.removedOnCompletion = NO;
animation.fillMode = kCAFillModeForwards;
animation.autoreverses = NO;
[calayer addAnimation:animation forKey:#"rotate"];
Is there anything missing on my code? thanks
What's happening is that you're seeing the animation in the presentation layer. However, that doesn't update the actual position of your layer. So, once the animation finishes, you see the layer as it was because it hasn't changed.
It's really worth reading the "Core Animation Rendering Architecture". Otherwise this can be very confusing.
To fix it, set a delegate to your CABasicAnimation as follows:
[animation setDelegate:self];
Then, create a method to set your target properties that you want when the animation completes. Now, here's the confusing part. You should do this on animationDidStart not animationDidStop. Otherwise, the presentation layer animation will finish, and you'll get a flicker as you see the calayer in the original position then it jumps - without animation - to the target position. Try it with animationDidStop and you'll see what I mean.
I hope that's not too confusing!
- (void)animationDidStart:(CAAnimation *)theAnimation
{
[calayer setWhateverPropertiesExpected];
}
EDIT:
I later discovered that Apple recommend a much better way to do this.
Oleg Begemann has a nice description of the correct technique in his blog post Prevent Layers from Snapping Back to Original Values When Using Explicit CAAnimations
Basically what you do is before you start the animation, you take a note of the layer's current value, i.e., the original value:
// Save the original value
CGFloat originalY = layer.position.y;
Next, set the toValue on the layer's model. Therefore the layer model has the final value of whatever animation you are about to do:
// Change the model value
layer.position = CGPointMake(layer.position.x, 300.0);
Then, you set the animation up with the animation fromValue being that original value that you noted above:
CABasicAnimation *animation = [CABasicAnimation animationWithKeyPath:#"position.y"];
// Now specify the fromValue for the animation because
// the current model value is already the correct toValue
animation.fromValue = #(originalY);
animation.duration = 1.0;
// Use the name of the animated property as key
// to override the implicit animation
[layer addAnimation:animation forKey:#"position"];
Note that code in edit above was copy/pasted from Ole Begemann's blog for clarity
If you want the animation to start from where it has ended, then set the fromValue property to the CALayer's current rotation.
Obtaining that value is tricky, but this SO post shows you how: https://stackoverflow.com/a/6706604/1072846