iOS 实现类似雷达效果的核心代码

 -(void)drawRect:(CGRect)rect
 {
     [[UIColor clearColor]setFill];
     UIRectFill(rect);
     NSInteger pulsingCount = ;
     double animationDuration = ;

     CALayer * animationLayer = [[CALayer alloc]init];
     self.animationLayer = animationLayer;

     for (int i = ; i < pulsingCount; i++) {
         CALayer * pulsingLayer = [[CALayer alloc]init];
         pulsingLayer.frame = CGRectMake(, , rect.size.width, rect.size.height);
         pulsingLayer.backgroundColor = [UIColor colorWithRed:92.0/255.0 green:181.0/255.0 blue:217.0/255.0 alpha:1.0].CGColor;
         pulsingLayer.borderColor = [UIColor colorWithRed:92.0/255.0 green:181.0/255.0 blue:217.0/255.0 alpha:1.0].CGColor;
         pulsingLayer.borderWidth = 1.0;
         pulsingLayer.cornerRadius = rect.size.height/;

         CAMediaTimingFunction * defaultCurve = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionLinear];

         CAAnimationGroup * animationGroup = [[CAAnimationGroup alloc]init];
         animationGroup.fillMode = kCAFillModeBoth;
         animationGroup.beginTime = CACurrentMediaTime() + (double)i * animationDuration/(double)pulsingCount;
         animationGroup.duration = animationDuration;        animationGroup.repeatCount = HUGE_VAL;
         animationGroup.timingFunction = defaultCurve;

         CABasicAnimation * scaleAnimation = [CABasicAnimation animationWithKeyPath:@"transform.scale"];
         scaleAnimation.autoreverses = NO;
         scaleAnimation.fromValue = [NSNumber numberWithDouble:0.2];
         scaleAnimation.toValue = [NSNumber numberWithDouble:1.0];

         CAKeyframeAnimation * opacityAnimation = [CAKeyframeAnimation animationWithKeyPath:@"opacity"];
         opacityAnimation.values = @[[NSNumber numberWithDouble:1.0],[NSNumber numberWithDouble:0.5],[NSNumber numberWithDouble:0.3],[NSNumber numberWithDouble:0.0]];
         opacityAnimation.keyTimes = @[[NSNumber numberWithDouble:0.0],[NSNumber numberWithDouble:0.25],[NSNumber numberWithDouble:0.5],[NSNumber numberWithDouble:1.0]];
         animationGroup.animations = @[scaleAnimation,opacityAnimation];

         [pulsingLayer addAnimation:animationGroup forKey:@"pulsing"];
         [animationLayer addSublayer:pulsingLayer];
     }
     self.animationLayer.zPosition = -;//重新加载时，使动画至底层
     [self.layer addSublayer:self.animationLayer];

     CALayer * thumbnailLayer = [[CALayer alloc]init];
     thumbnailLayer.backgroundColor = [UIColor whiteColor].CGColor;
     CGRect thumbnailRect = CGRectMake(, , , );
     thumbnailRect.origin.x = (rect.size.width - thumbnailRect.size.width)/2.0;
     thumbnailRect.origin.y = (rect.size.height - thumbnailRect.size.height)/2.0;
     thumbnailLayer.frame = thumbnailRect;
     thumbnailLayer.cornerRadius = 23.0;
     thumbnailLayer.borderWidth = 1.0;
     thumbnailLayer.masksToBounds = YES;
     thumbnailLayer.borderColor = [UIColor whiteColor].CGColor;
     UIImage * thumbnail = self.thumbnailImage;
     thumbnailLayer.contents = (id)thumbnail.CGImage;
     thumbnailLayer.zPosition = -;
     [self.layer addSublayer:thumbnailLayer];
 }