Core Animation之多种动画效果
前面介绍了Core Animation基础知识，还有CALayer的简单使用，最终还是有要动画的滴，这里列出几个动画效果，参考下能加深对Core Animation的认识和理解
1、把图片移到右下角变小透明
使用CAAnimationGroup叠加动画效果，就是下面按钮《把图片移到右下角变小透明》描述的效果：
、
上面三个图是动画的三个状态，实现代码如下：
- (void)viewDidLoad
{
[super viewDidLoad];
self.imageView = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"snaguosha.png"]];
self.imageView.frame = CGRectMake(10, 10, 128, 192);
[self.view addSubview:self.imageView];
}
- (IBAction)tranAction:(id)sender {
CGPoint fromPoint = self.imageView.center;
//路径曲线
UIBezierPath *movePath = [UIBezierPath bezierPath];
[movePath moveToPoint:fromPoint];
CGPoint toPoint = CGPointMake(300, 460);
[movePath addQuadCurveToPoint:toPoint
controlPoint:CGPointMake(300,0)];
//关键帧
CAKeyframeAnimation *moveAnim = [CAKeyframeAnimation animationWithKeyPath:@"position"];
moveAnim.path = movePath.CGPath;
moveAnim.removedOnCompletion = YES;
//旋转变化
CABasicAnimation *scaleAnim = [CABasicAnimation animationWithKeyPath:@"transform"];
scaleAnim.fromValue = [NSValue valueWithCATransform3D:CATransform3DIdentity];
//x，y轴缩小到0.1,Z 轴不变
scaleAnim.toValue = [NSValue valueWithCATransform3D:CATransform3DMakeScale(0.1, 0.1, 1.0)];
scaleAnim.removedOnCompletion = YES;
//透明度变化
CABasicAnimation *opacityAnim = [CABasicAnimation animationWithKeyPath:@"alpha"];
opacityAnim.fromValue = [NSNumber numberWithFloat:1.0];
opacityAnim.toValue = [NSNumber numberWithFloat:0.1];
opacityAnim.removedOnCompletion = YES;
//关键帧，旋转，透明度组合起来执行
CAAnimationGroup *animGroup = [CAAnimationGroup animation];
animGroup.animations = [NSArray arrayWithObjects:moveAnim, scaleAnim,opacityAnim, nil];
animGroup.duration = 1;
[self.imageView.layer addAnimation:animGroup forKey:nil];
}
代码解析：上面关键帧设置了动画的路径，scaleAnim设置了缩小，opacityAnim设置了透明度的变化。把三个动画组合到：animGroup。
在把animGroup添加到imageView.layer层的动画里。于是动画效果就有了。
2、旋转并向右移动
- (IBAction)RightRotateAction:(id)sender {
CGPoint fromPoint = self.imageView.center;
UIBezierPath *movePath = [UIBezierPath bezierPath];
[movePath moveToPoint:fromPoint];
CGPoint toPoint = CGPointMake(fromPoint.x +100 , fromPoint.y ) ;
[movePath addLineToPoint:toPoint];
CAKeyframeAnimation *moveAnim = [CAKeyframeAnimation animationWithKeyPath:@"position"];
moveAnim.path = movePath.CGPath;
CABasicAnimation *TransformAnim = [CABasicAnimation animationWithKeyPath:@"transform"];
TransformAnim.fromValue = [NSValue valueWithCATransform3D:CATransform3DIdentity];
//沿Z轴旋转
TransformAnim.toValue = [NSValue valueWithCATransform3D: CATransform3DMakeRotation(M_PI,0,0,1)];
//沿Y轴旋转
// scaleAnim.toValue = [NSValue valueWithCATransform3D: CATransform3DMakeRotation(M_PI,0,1.0,0)];
//沿X轴旋转
// TransformAnim.toValue = [NSValue valueWithCATransform3D: CATransform3DMakeRotation(M_PI,1.0,0,0)];
TransformAnim.cumulative = YES;
TransformAnim.duration =3;
//旋转2遍，360度
TransformAnim.repeatCount =2;
self.imageView.center = toPoint;
TransformAnim.removedOnCompletion = YES;
CAAnimationGroup *animGroup = [CAAnimationGroup animation];
animGroup.animations = [NSArray arrayWithObjects:moveAnim, TransformAnim, nil];
animGroup.duration = 6;
[self.imageView.layer addAnimation:animGroup forKey:nil];
}
代码解析:可能你没注意到，CATransform3DMakeRotation，这返回的是旋转的值。上面的动画效果里返回的是CATransform3DMakeScale缩放的值。
向右移动是因为关键帧使用了路径为直线的路径。
3、旋转并消除边缘锯齿
- (IBAction)Rotate360Action:(id)sender {
//图片旋转360度
CABasicAnimation *animation = [ CABasicAnimation
animationWithKeyPath: @"transform" ];
animation.fromValue = [NSValue valueWithCATransform3D:CATransform3DIdentity];
//围绕Z轴旋转，垂直与屏幕
animation.toValue = [ NSValue valueWithCATransform3D:
CATransform3DMakeRotation(M_PI, 0, 0, 1.0) ];
animation.duration = 3;
//旋转效果累计，先转180度，接着再旋转180度，从而实现360旋转
animation.cumulative = YES;
animation.repeatCount = 2;
//在图片边缘添加一个像素的透明区域，去图片锯齿
CGRect imageRrect = CGRectMake(0, 0, self.imageView.frame.size.width, self.imageView.frame.size.height);
UIGraphicsBeginImageContext(imageRrect.size);
[self.imageView.image drawInRect:CGRectMake(1,1,self.imageView.frame.size.width-2,self.imageView.frame.size.height-2)];
self.imageView.image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
[self.imageView.layer addAnimation:animation forKey:nil];
}
如果你仔细观察，会看到第二个动画里在旋转时，图片边缘是有锯齿的，如何消除呢？在图片边缘添加一个像素的透明区域，去图片锯齿。UIGraphicsBeginImageContext 开始图片内容
UIGraphicsGetImageFromCurrentImageContext 获取当前内容作为图片，
UIGraphicsEndImageContext结束。是和UIGraphicsBeginImageContext配套使用的。
4、吃豆人动画
这个有点复杂，首先说下实现的步骤：
- 画一个吃豆人开口的路径：pacmanOpenPath
- 画一个吃豆人闭口的路径：pacmanClosedPath
- 新建一个闭口的吃豆人头的层：shapeLayer
- 把开口和闭口路径设置成CABasicAnimation *chompAnimation动画的起点和终点，这样循环就能出现咬牙的动画了。
- 最后设置一个路径为关键帧，让吃豆人在这条路径上行动。
代码如下：
- (void)animationInit
{
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];
[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];
[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];
}
- (void)startAnimation {
// 创建咬牙动画
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(0, 100)];
[path addLineToPoint:CGPointMake(300, 100)];
[path addLineToPoint:CGPointMake(300, 200)];
[path addLineToPoint:CGPointMake(0, 200)];
[path addLineToPoint:CGPointMake(0, 300)];
[path addLineToPoint:CGPointMake(300, 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"];
}
- (void)viewDidLoad
{
[super viewDidLoad];
[self animationInit];
}
还需要添加一个宏：
#define DEGREES_TO_RADIANS(x) (3.14159265358979323846 * x / 180.0) 计算角度转换
添加了个手势，点一下屏幕，吃豆人就动起来了。效果：
原作者，容芳志 (http://blog.csdn.net/totogo2010)
