计算偏移的方法直接用；

+(void)animationView:(UIScrollView *)anmaView activeRect:(CGRect)filedRect

{

//    CGRect filedRect=filed.frame;

    CGPoint point=anmaView.contentOffset;

//    计算出距离屏幕上方的相对坐标高度

    float  realDis=filedRect.origin.y-point.y; 

//    计算到目标点的距离的绝对值

    float distance=fabsf(realDis-FILED_POSITION);

    ihope(@"%f", distance);

    if (realDis>FILED_POSITION) {

        point.y+=distance;

    }else{

        point.y-=distance;

    }

    [UIView beginAnimations:nil context:nil];

    [UIView setAnimationDuration:0.5];

    anmaView.contentOffset=point;

    [UIView commitAnimations];

}