How do I restart a CALayer animation going on? - ios

Question

Apple mentions these two methods for pausing and resuming a CALayer animation going on
-(void)pauseLayer:(CALayer*)layer {
CFTimeInterval pausedTime = [layer convertTime:CACurrentMediaTime() fromLayer:nil];
layer.speed = 0.0;
layer.timeOffset = pausedTime;
}
-(void)resumeLayer:(CALayer*)layer {
CFTimeInterval pausedTime = [layer timeOffset];
layer.speed = 1.0;
layer.timeOffset = 0.0;
layer.beginTime = 0.0;
CFTimeInterval timeSincePause = [layer convertTime:CACurrentMediaTime() fromLayer:nil] - pausedTime;
layer.beginTime = timeSincePause;
}
but how do I restart the animation?
this other SO question has nothing to do with what I need.

Answer 1

I have adopted code from blog in ViewController. Take a look at method [resetEmitterLayer:]. In your case all you need to do to reset animation is as follow:
Remove emitter layer from super layer.
Recreate emitter layer.
Add new emitter layer to the layer tree.
See ViewController implementation below
#import "EmitterViewController.h"
#import <QuartzCore/QuartzCore.h>
#interface EmitterViewController ()
#property (nonatomic, strong) CAEmitterLayer *emitterLayer;
#end
#implementation EmitterViewController
- (void)viewDidLoad {
[super viewDidLoad];
// Do any additional setup after loading the view.
self.emitterLayer = [self createEmitterLayer];
[self.view.layer addSublayer:self.emitterLayer];
}
-(CAEmitterLayer *)createEmitterLayer {
CAEmitterLayer *emitterLayer = [CAEmitterLayer layer];
emitterLayer.emitterPosition = CGPointMake(self.view.bounds.size.width / 2, self.view.bounds.origin.y);
emitterLayer.emitterZPosition = 10;
emitterLayer.emitterSize = CGSizeMake(self.view.bounds.size.width, 0);
emitterLayer.emitterShape = kCAEmitterLayerSphere;
CAEmitterCell *emitterCell = [CAEmitterCell emitterCell];
emitterCell.scale = 0.1;
emitterCell.scaleRange = 0.2;
emitterCell.emissionRange = (CGFloat)M_PI_2;
emitterCell.lifetime = 5.0;
emitterCell.birthRate = 10;
emitterCell.velocity = 200;
emitterCell.velocityRange = 50;
emitterCell.yAcceleration = 250;
emitterCell.contents = (id)[[UIImage imageNamed:#"WaterDrop.png"] CGImage];
emitterLayer.emitterCells = [NSArray arrayWithObject:emitterCell];
return emitterLayer;
}
-(IBAction)pauseEmitterLayer:(id)sender
{
CFTimeInterval pausedTime = [self.emitterLayer convertTime:CACurrentMediaTime() fromLayer:nil];
self.emitterLayer.speed = 0.0;
self.emitterLayer.timeOffset = pausedTime;
}
-(IBAction)resumeEmitterLayer:(id)sender
{
CFTimeInterval pausedTime = [self.emitterLayer timeOffset];
self.emitterLayer.speed = 1.0;
self.emitterLayer.timeOffset = 0.0;
self.emitterLayer.beginTime = 0.0;
CFTimeInterval timeSincePause = [self.emitterLayer convertTime:CACurrentMediaTime() fromLayer:nil] - pausedTime;
self.emitterLayer.beginTime = timeSincePause;
}
-(IBAction)resetEmitterLayer:(id)sender
{
[self.emitterLayer removeFromSuperlayer];
self.emitterLayer = [self createEmitterLayer];
[self.view.layer addSublayer:self.emitterLayer];
}
#end