弹性动画

http://blog.csdn.net/youshaoduo/article/details/53203211

[UIView animateWithDuration:0.3 delay:0.1 usingSpringWithDamping:0.6 initialSpringVelocity:3.0 options:UIViewAnimationOptionCurveLinear animations:^{
        __weakSelf.articleBtn.y = yPositio;
    } completion:^(BOOL finished) {
        self.userInteractionEnabled=YES;
    }];

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