动画有点抖s

gif.gif

给UIView添加一个分类

#import <UIKit/UIKit.h>

@interface UIView (RadarAnimation)

@property(nonatomic,strong)UIColor *radarColor; //扩散颜色
@property(nonatomic,assign)UIColor *radarBorderColor; //扩散边界颜色
-(void)addRadarAnimation;
@end

调用方法：

 button.radarColor = LBColor(237, 174, 130, 1);
 button.radarBorderColor = LBColor(237, 174, 130, 0.5);
  [button addRadarAnimation];

添加动画的方法,创建三个layer，只不过，开始动画的时间要错开形成这个效果：

-(void)Animation{
    NSInteger pulsingCount = 3;
    double animationDuration = 2;
    
    CALayer * animationLayer = [[CALayer alloc]init];
    
    for (int i = 0; i < pulsingCount; i++) {
        CALayer * pulsingLayer = [[CALayer alloc]init];
        pulsingLayer.frame = CGRectMake(0, 0, self.frame.size.width, self.frame.size.height);
        pulsingLayer.backgroundColor = self.radarColor.CGColor;
        pulsingLayer.borderColor = self.radarBorderColor.CGColor;


        pulsingLayer.borderWidth = 1.0;
        pulsingLayer.cornerRadius = self.frame.size.height/2;
        
        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:1];
        scaleAnimation.toValue = [NSNumber numberWithDouble:1.5];
        
        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];
    }
        animationLayer.zPosition = -1;//重新加载时，使动画至底层
    [self.layer addSublayer:animationLayer];

}

为了防止动画进入后台假死，需要监听通知：
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(appDidEnterPlayground) name:UIApplicationDidBecomeActiveNotification object:nil];

demo 地址：漫漫的demo