iOS：滚动表格视图时隐藏和显示自定义导航栏

Question

我有一个自定义导航栏，我试图在滚动时隐藏它并在滚动停止时显示。

- (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView
{
        self.navigationBView.hidden = YES;
        self.bTableView.frame = CGRectMake(0, 0, CGRectGetWidth(self.view.frame), CGRectGetHeight(self.view.frame));
}

- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView
{
    self.navigationBView.hidden = NO;
     self.bTableView.frame = CGRectMake(0, CGRectGetHeight(self.navigationBView.frame), CGRectGetWidth(self.view.frame), CGRectGetHeight(self.view.frame) - CGRectGetHeight(self.navigationBView.frame));
}

但问题是我还使用了UIRefreshControl 进行拉动刷新方法。当我尝试拖动 tableView 进行刷新时，它会调用

- (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView

并隐藏导航栏。有没有一种方法可以检查用户是否从屏幕顶部（即第一个表格单元格）下拉？

我试过了

- (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView
{
    if (scrollView.contentOffset.y != 0)
    {
        self.navigationBView.hidden = YES;
        self.bTableView.frame = CGRectMake(0, 0, CGRectGetWidth(self.view.frame), CGRectGetHeight(self.view.frame));
    }

}

但是当用户向下滚动时，这不会隐藏导航栏。有什么办法可以解决这个问题？

Answer 1

只需在scrollViewWillBeginDragging 中将您的条件!= 更改为>=

- (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView
{
    if (scrollView.contentOffset.y >= 0)
    {
        self.navigationBView.hidden = YES;
        self.bTableView.frame = CGRectMake(0, 0, CGRectGetWidth(self.view.frame), CGRectGetHeight(self.view.frame));
    }

}

Answer 2

你可以试试下面的代码，看看这是否适合你。

@property (nonatomic) CGFloat lastContentOffset; //是一个 iVar

- (void)scrollViewDidScroll:(UIScrollView *)scrollView
{
    float movement = fabsf(self.lastContentOffset-scrollView.contentOffset.y);
    if (self.lastContentOffset > scrollView.contentOffset.y)
    {
        //user is scrolling up through the list
        if (movement > 15 && movement < 40)
        {
            //show the navigation bar 
        }

    }
    else if (self.lastContentOffset < scrollView.contentOffset.y)
    {
        //user is scrolling down through the list
        if (movement > 15 && movement < 40)
        {
           //show the navigation bar 
        }
    }

    self.lastContentOffset = scrollView.contentOffset.y;
}

- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView
{    
   //show the navigation bar 
}