IOS学习动画二之 Core Animation (2)

二、动手干活比如我们想实现一个类似心跳的缩放动画可以这么做，分为演员初始化、设定剧本、电影开拍三个步骤：

- (void)initScaleLayer {
//演员初始化
CALayer *scaleLayer = [[CALayer alloc] init];
scaleLayer.backgroundColor = [UIColor blueColor].CGColor;
scaleLayer.frame = CGRectMake(60, 20 + kYOffset, 50, 50);
scaleLayer.cornerRadius = 10;
[self.view.layer addSublayer:scaleLayer];
[scaleLayer release];

//设定剧本
CABasicAnimation *scaleAnimation = [CABasicAnimation animationWithKeyPath:@"transform.scale"];
scaleAnimation.fromValue = [NSNumber numberWithFloat:1.0];
scaleAnimation.toValue = [NSNumber numberWithFloat:1.5];
scaleAnimation.autoreverses = YES;
scaleAnimation.fillMode = kCAFillModeForwards;
scaleAnimation.repeatCount = MAXFLOAT;
scaleAnimation.duration = 0.8;

//开演
[scaleLayer addAnimation:scaleAnimation forKey:@"scaleAnimation"];
}

想要实现不同的效果，最关键的地方在于CABasicAnimation对象的初始化方式中keyPath的设定。在iOS中有以下几种不同的keyPath，代表着不同的效果：

此外，我们还可以利用GroupAnimation实现多种动画的组合，在GroupAnimation中的各个动画类型是同时进行的。

- (void)initGroupLayer
{
//演员初始化
CALayer *groupLayer = [[CALayer alloc] init];
groupLayer.frame = CGRectMake(60, 340+100 + kYOffset, 50, 50);
groupLayer.cornerRadius = 10;
groupLayer.backgroundColor = [[UIColor purpleColor] CGColor];
[self.view.layer addSublayer:groupLayer];
[groupLayer release];

//设定剧本
CABasicAnimation *scaleAnimation = [CABasicAnimation animationWithKeyPath:@"transform.scale"];
scaleAnimation.fromValue = [NSNumber numberWithFloat:1.0];
scaleAnimation.toValue = [NSNumber numberWithFloat:1.5];
scaleAnimation.autoreverses = YES;
scaleAnimation.repeatCount = MAXFLOAT;
scaleAnimation.duration = 0.8;

CABasicAnimation *moveAnimation = [CABasicAnimation animationWithKeyPath:@"position"];
moveAnimation.fromValue = [NSValue valueWithCGPoint:groupLayer.position];
moveAnimation.toValue = [NSValue valueWithCGPoint:CGPointMake(320 - 80,
groupLayer.position.y)];
moveAnimation.autoreverses = YES;
moveAnimation.repeatCount = MAXFLOAT;
moveAnimation.duration = 2;

CABasicAnimation *rotateAnimation = [CABasicAnimation animationWithKeyPath:@"transform.rotation.x"];
rotateAnimation.fromValue = [NSNumber numberWithFloat:0.0];
rotateAnimation.toValue = [NSNumber numberWithFloat:6.0 * M_PI];
rotateAnimation.autoreverses = YES;
rotateAnimation.repeatCount = MAXFLOAT;
rotateAnimation.duration = 2;

CAAnimationGroup *groupAnnimation = [CAAnimationGroup animation];
groupAnnimation.duration = 2;
groupAnnimation.autoreverses = YES;
groupAnnimation.animations = @[moveAnimation, scaleAnimation, rotateAnimation];
groupAnnimation.repeatCount = MAXFLOAT;
//开演
[groupLayer addAnimation:groupAnnimation forKey:@"groupAnnimation"];
}