ios 如何令一张图片左右晃动

//开始动画

CABasicAnimation *momAnimation = [CABasicAnimation animationWithKeyPath:@"transform.rotation.z"];

    momAnimation.fromValue = [NSNumber numberWithFloat:-0.3];

    momAnimation.toValue = [NSNumber numberWithFloat:0.3];

    momAnimation.duration = 0.5;

    momAnimation.repeatCount = CGFLOAT_MAX;

    momAnimation.autoreverses = YES;

    momAnimation.delegate = self;

    [_momImageView.layer addAnimation:momAnimation forKey:@"animateLayer"];

//暂停动画，图片未复位

-(void)pauseLayer:(CALayer*)layer

{

    CFTimeInterval pausedTime = [layer convertTime:CACurrentMediaTime() fromLayer:nil];

    layer.speed = 0.0;

    layer.timeOffset = pausedTime;

}

//重新开始动画

-(void)resumeLayer:(CALayer*)layer{

    CFTimeInterval pausedTime = [layer timeOffset];

    layer.speed = 1.0;

    layer.timeOffset = 0.0;

    layer.beginTime = 0.0;

    CFTimeInterval timeSincePause = [layer convertTime:CACurrentMediaTime() fromLayer:nil] - pausedTime;

    layer.beginTime = timeSincePause;

}

//移除动画，图片复位

[self.momImageView.layer removeAllAnimations];