tableview（scrollview） （使其停止滑动 && 计算拉动距离）

再仔细说下：

1：想求出拉动tableview(scrollview)移动的距离。

2：使它被拉动后在被拉动的状态下停下的方法。
{
    aTopBtn = [UIButton buttonWithType:UIButtonTypeCustom];
    aTopBtn.frame = CGRectMake(ScreenWidth-50,ScreenHeight-64-105, 35, 35);
    aTopBtn.backgroundColor = [UIColor clearColor];
    aTopBtn.hidden=YES;
    [aTopBtn setImage:[UIImage imageNamed:@"zs_shanghuabiao"] forState:UIControlStateNormal];
    [aTopBtn addTarget:self action:@selector(aToping:) forControlEvents:UIControlEventTouchUpInside];
    [self.view addSubview:aTopBtn];
   
}

- (void)scrollViewDidScroll:(UIScrollView *)scrollView{

NSLog(@"scrollView.contentOffset.y%f",scrollView.contentOffset.y);
    if (scrollView.contentOffset.y>0) {
        aTopBtn.frame = CGRectMake(ScreenWidth-50,ScreenHeight-64-105, 35, 45);
        aTopBtn.hidden=NO;
        [aTopBtn setImage:[UIImage imageNamed:@"zs_huitou"] forState:UIControlStateNormal];

} else {
        aTopBtn.frame = CGRectMake(ScreenWidth-50,ScreenHeight-64-105, 35, 35);
        aTopBtn.hidden=YES;
        [aTopBtn setImage:[UIImage imageNamed:@"zs_shanghuabiao"] forState:UIControlStateNormal];
    }
}