iOS: Core Animation Example: eggs falling out of a tree

ios_coreanimation_eggs.m

// Core Animation Example: eggs falling out of a tree
// This was glommed from iphonedevsdk: http://www.iphonedevsdk.com/forum/iphone-sdk-development/65632-animation-sample-code-our-newest-app.html

// This is the main animation routine.

- (IBAction) doorEasterEggAction;
{
  //treeDoorImageView
  CATransform3D theTransform;
  UIImageView* anEgg;

  
  CABasicAnimation *rotateAnimation;
  
  switch (animationStep) 
  {
    case 0:
      animationStep++;
      
      //-----------------------
      //Create 2 sounds players so we can alternate between them and keep up with 
      //the pace of egg launching
      self.popSoundPlayer1 = [Utils audioPlayerFromFilenameInBundle: @"pop sound" 
                                                            ofType: @"mp3"];
      self.popSoundPlayer2 = [Utils audioPlayerFromFilenameInBundle: @"pop sound" 
                                                             ofType: @"mp3"];
      [self.popSoundPlayer1 prepareToPlay];
      [self.popSoundPlayer2 prepareToPlay];
    //---------------------

      treeDoorButton.enabled = FALSE;  //Disable the hidden button during the animation.
      
      
      //Open the door.
      rotateAnimation = [CABasicAnimation animation];
      rotateAnimation.keyPath = @"transform";
      rotateAnimation.fromValue = [NSValue valueWithCATransform3D:CATransform3DIdentity];
      
      //Pivot on the right edge (y axis rotation)
      theTransform = CATransform3DRotate(CATransform3DIdentity, degreesToRadians(70), 0, 1, 0);
      
      rotateAnimation.toValue = [NSValue valueWithCATransform3D:theTransform];
      
      rotateAnimation.duration = 0.5;
      
      // leaves presentation layer in final state; preventing snap-back to original state
      rotateAnimation.removedOnCompletion = NO;
      rotateAnimation.fillMode = kCAFillModeBoth; 
      
      rotateAnimation.repeatCount = 0;
      rotateAnimation.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseInEaseOut];
      rotateAnimation.delegate = self;
      [treeDoorImageView.layer addAnimation:rotateAnimation forKey:@"transform"];
      break;
      
    case 1:
      //Pause briefly after the door opens.
      animationStep++;
      eggCount = 101;
      [self performSelector: @selector(doorEasterEggAction) withObject: nil afterDelay: 0.2];
      break;
      
    case 2:
      //Move each egg onto the screen.
      if (eggCount <= 134)
      {
        [self animateEgg];
        eggCount++;
      }
      else
      {
        //After we've started the last egg moving, pause to let them all finish animating
        animationStep++;
        eggCount--;

        [self performSelector: @selector(doorEasterEggAction) withObject: nil afterDelay: 1.5];
      }
      
      break;
      
    case 3:    
      //Now make the eggs go away one at a time.
      anEgg = (UIImageView*)[self.view viewWithTag: eggCount];
      if (anEgg && [anEgg isMemberOfClass: [UIImageView class]])
      {
        [UIView beginAnimations: [NSString stringWithFormat: @"Egg %d", eggCount] context: nil];
        [UIView setAnimationDuration: .2];

        anEgg.alpha = 0;
        anEgg.transform = CGAffineTransformMakeScale(.01, .01);

        [UIView commitAnimations];
        [self performSelector: @selector(doorEasterEggAction) withObject: nil afterDelay: .05];
        
        eggCount--;
        if (eggCount < 101)
          animationStep++;
      }
      break;
    case 4:
      //Pause briefly after the last egg has gone away.
      animationStep++;
      [self performSelector: @selector(doorEasterEggAction) withObject: nil afterDelay: 0.5];
      break;

    case 5:
      animationStep++;
      
      //First restore all the eggs to their starting state
      for (eggCount = 101; eggCount <= 134; eggCount++)
      {
        anEgg = (UIImageView*)[self.view viewWithTag: eggCount];
        if (anEgg && [anEgg isMemberOfClass: [UIImageView class]])
        {
          anEgg.alpha = 1.0;
          anEgg.transform = CGAffineTransformIdentity;
          anEgg.hidden = TRUE;
        }
      }
      
      //Now close the door.
      rotateAnimation = [CABasicAnimation animation];
      rotateAnimation.keyPath = @"transform";
      
      //Pivot on the right edge (y axis rotation)
      //  CGFloat width = treeDoorImageView.frame.size.width / 2;
      //  theTransform = CATransform3DTranslate(theTransform, width, 0, 0);
      theTransform = CATransform3DRotate(CATransform3DIdentity, degreesToRadians(70), 0, 1, 0);
      
      rotateAnimation.fromValue = [NSValue valueWithCATransform3D:theTransform];
      rotateAnimation.toValue = [NSValue valueWithCATransform3D:CATransform3DIdentity];

      rotateAnimation.duration = 0.5;
      
      rotateAnimation.removedOnCompletion = YES;
      // leaves presentation layer in final state; preventing snap-back to original state
      rotateAnimation.fillMode = kCAFillModeBoth; 
      rotateAnimation.repeatCount = 0;
      rotateAnimation.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseInEaseOut];
      rotateAnimation.delegate = self;
      [treeDoorImageView.layer addAnimation:rotateAnimation forKey:@"transform"];
      break;
      
    case 6:
      //Finally, restore everything to it's starting state and renable the hidden button.
      [treeDoorImageView.layer removeAllAnimations];
      treeDoorButton.enabled = TRUE;
      animationStep = 0;
      self.popSoundPlayer1 = nil;
      self.popSoundPlayer2 = nil;
      break;

  }
  
  
}

//This is the CAAnimation delegate method that gets called once the "open the door" animation completes. 
/It simply calls the main animation method again.
- (void)animationDidStop:(CAAnimation *)theAnimation finished:(BOOL)flag
{
  [self doorEasterEggAction];
}


//This is the code that animates a single egg moving in an arc from the open door to it's final position.
- (void) animateEgg;
{
  CGPoint endPoint;
  UIImageView* anEgg;
  CGMutablePathRef aPath;
  CGFloat arcTop = 185;
  CGFloat duration = 0.75;
  
  //Use the egg count as a tag to find the egg's UIImageView in it's superview
  anEgg = (UIImageView*)[self.view viewWithTag: eggCount];
  if (anEgg && [anEgg isMemberOfClass: [UIImageView class]])
  {
    //Get the egg's position and save it as the end point for the animation.
    endPoint = anEgg.center;
 
    //Create a CGPath that will describe the arc for this egg.
    aPath = CGPathCreateMutable();
    anEgg.hidden = FALSE;

    //Start each animation at the same point, the door of the tree.
    CGPathMoveToPoint(aPath, NULL, 170, 275);
    CGPathAddCurveToPoint(aPath, NULL, 170, arcTop, endPoint.x, arcTop, endPoint.x, endPoint.y);
    CAKeyframeAnimation* arcAnimation = [CAKeyframeAnimation animationWithKeyPath: @"position"];
    
    [arcAnimation setDuration: duration];
    [arcAnimation setAutoreverses: NO];
    arcAnimation.removedOnCompletion = NO;
    arcAnimation.fillMode = kCAFillModeBoth; 
    [arcAnimation setPath: aPath];
    CFRelease(aPath);
    
    //Alternate between 2 sound players so they can keep up with the rapid-fire egg launching
    if (eggCount %2 == 0)
      [self.popSoundPlayer1 play];
    else 
      [self.popSoundPlayer2 play];


    [anEgg.layer addAnimation: arcAnimation forKey: @"position"];
    anEgg.transform = CGAffineTransformMakeScale(.2, .2);
    
    [UIView beginAnimations: [NSString stringWithFormat: @"Egg %d", eggCount] context: nil];
    [UIView setAnimationDuration: duration];

    anEgg.transform = CGAffineTransformIdentity;
    [UIView commitAnimations];
    [self performSelector: @selector(doorEasterEggAction) withObject: nil 
      afterDelay: 0.07 + [Utils randomFloatPlusOrMinus: .03 ]];
  }
           
}