iOS 圆的放大动画效果

第一步：创建一个View，将这个View添加到当前的控制器

如：

CGFloat timeW = self.view.bounds.size.width;
timeAnimation * timean = [[timeAnimation alloc]initWithFrame:CGRectMake(0,0,timeW,timeW)];
    　timean.center = CGPointMake(self.view.bounds.size.width*0.5, self.view.bounds.size.height *0.5);
[self.view addSubview:timean];

第二步：在View的.m文件中添加如下代码

#define PI 3.14159265358979323846

#define kradius self.bounds.size.width*0.1

-(instancetype)initWithFrame:(CGRect)frame
{
    if (self = [super initWithFrame:frame]) {
        self.frame = frame;
        self.backgroundColor = [UIColor clearColor];
    }
    return self;
}
- (void)drawRect:(CGRect)rect {
    CGContextRef context = UIGraphicsGetCurrentContext();

    [self greenRound:context];
    self.alpha = 0.5;
    [self test];
}
-(void)test
{
    // 2.创建缩放动画对象
    CABasicAnimation *scale = [CABasicAnimation animation];
    scale.keyPath = @"transform.scale";
    scale.fromValue =[NSNumber numberWithFloat:0.0];
    scale.toValue =[NSNumber numberWithFloat:1.0];
    CABasicAnimation *scale1 = [CABasicAnimation animation];
    scale1.keyPath = @"opacity";
    scale1.fromValue =[NSNumber numberWithFloat:1.0];
    scale1.toValue =[NSNumber numberWithFloat:0.0];
    // 4.将所有的动画添加到动画组中
    CAAnimationGroup *group = [CAAnimationGroup animation];
    group.animations = @[scale,scale1];
    group.duration =.6;
    group.repeatCount = HUGE_VALF;
    group.removedOnCompletion = NO;
    group.fillMode = kCAFillModeForwards;
    [self.layer addAnimation:group forKey:nil];
}
/**画绿色的圆*/
-(void)greenRound:(CGContextRef)context
{
    CGContextSetRGBStrokeColor(context, 33/255.0, 177/255.0, 75/255.0, 1);//画笔线的颜色
    CGContextSetLineWidth(context, 4.0);//线的宽度
    // x,y为圆点坐标，radius半径，startAngle为开始的弧度，endAngle为 结束的弧度，clockwise 0为顺时针，1为逆时针。
    CGContextAddArc(context, self.bounds.size.width *0.5,self.bounds.size.height*0.5,self.bounds.size.width*0.21, 0, 2*PI, 0); //添加一个圆
    CGContextDrawPath(context, kCGPathStroke); //绘制路径
}