有时候在开发中， 需要我们实现一个晃动动画，
达到一个提示的效果，如下图所示

思路， 我们要实现的本质上是一个旋转动画，然后
设置一个旋转角度，以底部中间为中心旋转，
左右各有一个旋转的角度，并且旋转角度逐渐变小，
动画速度逐渐变快，即时间间隔逐渐减小

代码

#define radian(angle) ((angle) / 180.0 * M_PI)
- (void)setUpUI
{
    [self configCorners:UIRectCornerTopLeft | UIRectCornerTopRight | UIRectCornerBottomRight radius:6.5];
    self.layer.backgroundColor = [UIColor redColor].CGColor;
    self.textColor = [UIColor whiteColor];
    self.font = [UIFont systemFontOfSize:9];
    self.textAlignment = NSTextAlignmentCenter;
    self.layer.anchorPoint = CGPointMake(0.5, 1);
    self.layer.masksToBounds = YES;
    CGFloat width = [UIScreen mainScreen].bounds.size.width;
    CGFloat height = [UIScreen mainScreen].bounds.size.height;
    self.layer.position = CGPointMake(width / 2.f - 15, height/2.f + 5);
    [self addMoveAnimation:self];
   
}
    
- (void)addMoveAnimation:(UIView *)view
{
    CAKeyframeAnimation *animation = [CAKeyframeAnimation animation];
    animation.delegate = self;
    animation.keyPath = @"transform.rotation.z";
    animation.values = @[@(radian(0)), @(radian(-15)), @(radian(0)), @(radian(15)),@(radian(0)),@(radian(-10)), @(radian(0)), @(radian(10)),@(radian(0)),@(radian(-7)), @(radian(0)), @(radian(7)),@(radian(0)),@(radian(-3)), @(radian(0)), @(radian(3)),@(radian(0)),@(radian(-1)), @(radian(0)), @(radian(1)),@(radian(0))];
    animation.keyTimes = @[@0, @0.07, @0.14 , @0.21, @0.28, @0.35,@0.42, @0.49, @0.56, @0.63, @0.70, @0.75, @0.80, @0.85, @0.88,@0.91,@0.94, @0.96, @0.98,@0.99, @1];
    animation.duration = 1;
    // 动画的重复执行次数
    animation. repeatCount = 1;
    // 保持动画执行完毕后的状态
    animation.removedOnCompletion = YES;
    animation.fillMode = kCAFillModeRemoved;
    [view.layer addAnimation:animation forKey:@"shake_animation"];
}

#pragma mark - 动画代理

- (void)animationDidStop: (CAAnimation *)animation finished:(BOOL)flag
{
  dispatshafter_ 2, NSOperationQueuePriorityHigh, ^{
        [self addMoveAnimation:self];
    });
}