iOS UITextField输入错误的震动动画

//左右震动效果
- (void)shake:(UIView *)view {
    CGRect frame = view.frame;
    CAKeyframeAnimation *shakeAnimation = [CAKeyframeAnimation animationWithKeyPath:@"position"];
    
    CGMutablePathRef shakePath = CGPathCreateMutable();
    CGPathMoveToPoint(shakePath, NULL, frame.origin.x+frame.size.width/2, frame.origin.y+frame.size.height/2);
    int index;
    for (index = 3; index >=0; --index) {
        CGPathAddLineToPoint(shakePath, NULL, frame.origin.x+frame.size.width/2 - frame.size.width * 0.02f * index, frame.origin.y+frame.size.height/2);
        CGPathAddLineToPoint(shakePath, NULL, frame.origin.x+frame.size.width/2 + frame.size.width * 0.02f * index, frame.origin.y+frame.size.height/2);
    }
    CGPathCloseSubpath(shakePath);
    
    shakeAnimation.path = shakePath;
    shakeAnimation.duration = 0.5f;
    shakeAnimation.removedOnCompletion = YES;
    
    [view.layer addAnimation:shakeAnimation forKey:nil];
    CFRelease(shakePath);
}