Core Animation学习笔记三：CAkeyframeAnimation

CAkeyframeAnimation：提供了关键帧动画的支持。你可以为层属性指定key path来使其产生动画，这个数组的值保存了动画每个阶段的值，同时还有key frame的次数和时间函数。在动画运行的时候，数组中的每个值就会被轮流进行插值使用。

- (void)viewDidLoad {
    [super viewDidLoad];
    
    self.title = [[self class] displayName];
    
    self.view.backgroundColor = [UIColor blackColor];
    
    CGFloat radius = 30.0f;
    CGFloat diameter = radius * 2;
    CGPoint arcCenter = CGPointMake(radius, radius);
    
    // Create a UIBezierPath for Pacman's open state
    pacmanOpenPath = [[UIBezierPath bezierPathWithArcCenter:arcCenter
                                                               radius:radius 
                                                           startAngle:DEGREES_TO_RADIANS(35) 
                                                             endAngle:DEGREES_TO_RADIANS(315)
                                                            clockwise:YES] retain];    


    [pacmanOpenPath addLineToPoint:arcCenter];
    [pacmanOpenPath closePath];
    
    // Create a UIBezierPath for Pacman's close state
    pacmanClosedPath = [[UIBezierPath bezierPathWithArcCenter:arcCenter
                                                               radius:radius 
                                                           startAngle:DEGREES_TO_RADIANS(1) 
                                                             endAngle:DEGREES_TO_RADIANS(359) 
                                                            clockwise:YES] retain];
    [pacmanClosedPath addLineToPoint:arcCenter];
    [pacmanClosedPath closePath];    
    
    // Create a CAShapeLayer for Pacman, fill with yellow
    shapeLayer = [CAShapeLayer layer];
    shapeLayer.fillColor = [UIColor yellowColor].CGColor;
    shapeLayer.path = pacmanClosedPath.CGPath;
    shapeLayer.strokeColor = [UIColor grayColor].CGColor;
    shapeLayer.lineWidth = 1.0f;
    shapeLayer.bounds = CGRectMake(0, 0, diameter, diameter);
    shapeLayer.position = CGPointMake(-40, -100);
    [self.view.layer addSublayer:shapeLayer];
    
    SEL startSelector = @selector(startAnimation);
    UIGestureRecognizer *recognizer = [[UITapGestureRecognizer alloc] initWithTarget:self action:startSelector];
    [self.view addGestureRecognizer:recognizer];
    [recognizer release];
    
    // start animation after short delay
    [self performSelector:startSelector withObject:nil afterDelay:1.0];
}

- (void)startAnimation {

    // Create CHOMP CHOMP animation
    CABasicAnimation *chompAnimation = [CABasicAnimation animationWithKeyPath:@"path"];
    chompAnimation.duration = 0.25;
    
    chompAnimation.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionLinear];
    chompAnimation.repeatCount = HUGE_VALF;
    chompAnimation.autoreverses = YES;
    // Animate between the two path values
    chompAnimation.fromValue = (id)pacmanClosedPath.CGPath;
    chompAnimation.toValue = (id)pacmanOpenPath.CGPath;
    
    [shapeLayer addAnimation:chompAnimation forKey:@"chompAnimation"];
    
    // Create digital '2'-shaped path
    UIBezierPath *path = [UIBezierPath bezierPath];
    [path moveToPoint:CGPointMake(-40, 100)];
    [path addLineToPoint:CGPointMake(360, 100)];
    [path addLineToPoint:CGPointMake(360, 200)];
    [path addLineToPoint:CGPointMake(-40, 200)];
    [path addLineToPoint:CGPointMake(-40, 300)];
    [path addLineToPoint:CGPointMake(360, 300)];
    
    CAKeyframeAnimation *moveAnimation = [CAKeyframeAnimation animationWithKeyPath:@"position"];
    moveAnimation.path = path.CGPath;
    moveAnimation.duration = 8.0f;
    // Setting the rotation mode ensures Pacman's mouth is always forward.  This is a very convenient CA feature.
    moveAnimation.rotationMode = kCAAnimationRotateAuto;
    [shapeLayer addAnimation:moveAnimation forKey:@"moveAnimation"];

}