闲暇时间做了一个反馈手指点击屏幕的效果,用到了CAShapeLayer和基本的动画知识，模拟器上效果如下：

fingerWave.gif

• 这种效果使用在某些页面上肯定会给用户更有趣的体验，特别是面向儿童的app中。

具体的实现代码如下

• 首先监听控制器view的Tap事件

  UITapGestureRecognizer *tap = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(onTap:)];
    [self.view addGestureRecognizer:tap];

  - (void)onTap:(UITapGestureRecognizer*)sender {
    CGPoint center = [sender locationInView:sender.view];
    [FingerWaveView  showInView:self.view center:center];
  }

• FingerWaveView.h

  #import <UIKit/UIKit.h>
  @interface FingerWaveView : UIView
  + (instancetype)showInView:(UIView *)view center:(CGPoint)center;
  @end

• FingerWaveView.m

  #import "FingerWaveView.h"
  @interface FingerWaveView () <CAAnimationDelegate>
  {
    CGSize waveSize;
    NSTimeInterval duration;
  }
  @end
  @implementation FingerWaveView
  - (instancetype)initWithFrame:(CGRect)frame{
    self=[super initWithFrame:frame];
    if (self) {
        waveSize = CGSizeMake(150, 150);
        duration = 1.0;
    }
    return self;
  }
  + (instancetype)showInView:(UIView *)view center:(CGPoint)center {
    FingerWaveView *waveView = [FingerWaveView new];
    [waveView setframeWithCenter:center];
    [view addSubview:waveView];
    return waveView;
  }
  - (void)didMoveToSuperview{
    CAShapeLayer *waveLayer = [CAShapeLayer new];
    waveLayer.backgroundColor  = [UIColor clearColor].CGColor;
    waveLayer.opacity = 0.6;
    waveLayer.fillColor = [UIColor whiteColor].CGColor;
    [self.layer addSublayer:waveLayer];
    [self startAnimationInLayer:waveLayer];
  }
  - (void)startAnimationInLayer:(CALayer *)layer{
    UIBezierPath *beginPath = [UIBezierPath bezierPathWithArcCenter:[self pathCenter] radius:[self animationBeginRadius] startAngle:0 endAngle:M_PI*2 clockwise:YES];
    UIBezierPath *endPath = [UIBezierPath bezierPathWithArcCenter:[self pathCenter] radius:[self animationEndRadius] startAngle:0 endAngle:M_PI*2 clockwise:YES];
    CABasicAnimation *rippleAnimation = [CABasicAnimation animationWithKeyPath:@"path"];
    rippleAnimation.delegate = self;
    rippleAnimation.fromValue = (__bridge id _Nullable)(beginPath.CGPath);
    rippleAnimation.toValue = (__bridge id _Nullable)(endPath.CGPath);
    rippleAnimation.duration = duration;
    CABasicAnimation *opacityAnimation = [CABasicAnimation animationWithKeyPath:@"opacity"];
    opacityAnimation.delegate = self;
    opacityAnimation.fromValue = [NSNumber numberWithFloat:0.6];
    opacityAnimation.toValue = [NSNumber numberWithFloat:0.0];
    opacityAnimation.duration = duration;
    [layer addAnimation:rippleAnimation forKey:@"rippleAnimation"];
    [layer addAnimation:opacityAnimation forKey:@"opacityAnimation"];
  }
  - (void)setframeWithCenter:(CGPoint)center{
    CGRect frame = CGRectMake(center.x-waveSize.width*0.5, center.y-waveSize.height*0.5, waveSize.width, waveSize.height);
    self.frame = frame;;
  }
  - (CGFloat)animationBeginRadius{
    return waveSize.width*0.5*0.2;
  }
  - (CGFloat)animationEndRadius{
    return waveSize.width*0.5;
  }
  - (CGPoint)pathCenter{
    return CGPointMake(waveSize.width*0.5, waveSize.height*0.5);
  }
  #pragma mark - CAAnimationDelegate
  - (void)animationDidStop:(CAAnimation *)anim finished:(BOOL)flag{
    if (flag) {
        [self removeFromSuperview];
    }
  }
  @end

• 大家也可以DIY我的代码，做出很多其他的效果，比如改成其他的波纹颜色。

来自：http://www.jianshu.com/p/35e6f53ca0fe

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