I have an UIImageView spinning using the following code:
CABasicAnimation *rotation;
rotation = [CABasicAnimation animationWithKeyPath:#"transform.rotation"];
rotation.fromValue = [NSNumber numberWithFloat:0];
rotation.toValue = [NSNumber numberWithFloat:(2*M_PI)];
rotation.duration = 2.0;
rotation.repeatCount = HUGE_VALF;
[myView.layer addAnimation:rotation forKey:#"Spin"];
And I can stop it by running
[myView.layer removeAnimationForKey:#"Spin"];
However, when the animation stops, the image resets to where it started. This looks a little awkward if the image is mid-turn, so I would like for it to stop exactly where it is in the rotation. I assume this would require getting the current rotation amount just before stopping the animation, and then setting it back to that rotation amount instantly after stopping the animation. I do not know how to do this though.
There a couple ways of doing this. One way is my affecting the layers speed property which you can find an example of in the answer to this post: Is there a way to pause a CABasicAnimation?. But this way is more of a means to pause the animation.
Since you want to stop it, I recommend you keep calling removeAnimationForKey: like you are, and coupling it with a CATransform3D made to match the view's presentationLayer's transform before it stopped animating. Give it a try:
CATransform3D myTransform = [(CALayer*)[myView.layer presentationLayer] transform];
[myView.layer removeAnimationForKey:#"Spin"];
[myView.layer setTransform:myTransform];
Related
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.
I have a CAEmitterLayer and I'd like to have a simple animation run over the course of each particle's life.
As soon as particle pops in, I'd like it to scale up to about 1.2, then after a short time have it scale back to 1.0 and stay that way until it's lifetime expires.
I know about the scale, scaleRange and scaleSpeed properties of the CAEmitterCell but they're way too random for what I need.
Is this possible to do? I've tried adding a CABasicAnimation like this (my CAEmitterCell's name is "heart"):
CABasicAnimation *anim = [CABasicAnimation animationWithKeyPath:#"emitterCells.heart.scale"];
anim.fromValue = #(1.0);
anim.toValue = #(2.0);
anim.duration = 3.0;
anim.fillMode = kCAFillModeForwards;
anim.repeatCount = CGFLOAT_MAX;
[self.heartsEmitter addAnimation:anim forKey:#"scaleAnimation"];
but it doesn't work, the particles just appear at a random scale, they don't animate at all.
I'm not completely sure, but it seems to me that you are applying the animation to the emitter instead of the cells.
If the CAEmitterCell's name is heart try this: [self.heart addAnimation:anim forKey:#"scaleAnimation"];. Does this help?
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 using the following CABasicAnimation. But, its very slow..is there a way to speed it up ? Thanks.
- (void)spinLayer:(CALayer *)inLayer duration:(CFTimeInterval)inDuration
direction:(int)direction
{
CABasicAnimation* rotationAnimation;
// Rotate about the z axis
rotationAnimation =
[CABasicAnimation animationWithKeyPath:#"transform.rotation.z"];
// Rotate 360 degress, in direction specified
rotationAnimation.toValue = [NSNumber numberWithFloat: M_PI * 2.0 * direction];
// Perform the rotation over this many seconds
rotationAnimation.duration = inDuration;
// Set the pacing of the animation
rotationAnimation.timingFunction =
[CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionLinear];
// Add animation to the layer and make it so
[inLayer addAnimation:rotationAnimation forKey:#"rotationAnimation"];
}
Core Animation animations can repeat a number of times, by setting the repeatCount property on the animation.
So if you'd like to have an animation run for a total 80 seconds, you need to figure out a duration for one pass of the animation – maybe one full spin of this layer – and then set the duration to be that value. Then let the animation repeat that full spin several times to fill out your duration.
So something like this:
rotationAnimation.repeatCount = 8.0;
Alternatively, you can use repeatDuration to achieve a similar affect:
rotationAnimation.repeatDuration = 80.0;
In either case, you need to set the duration to the time of a single spin, and then repeat it using ONE of these methods. If you set both properties, the behavior is undefined. You can check out the documentation on CAMediaTiming here.