UIScrollView direction of scrolling

问题:

I would like to copy the effect seen in Pinterest app, where they hide top and bottom bars depending on the direction of scrolling. My question is: what is the correct way to determine which way the UIScrollView is scrolling?

回答1:

This is the solution:

-(void)scrollViewWillBeginDragging:(UIScrollView *)scrollView {
    pointNow = scrollView.contentOffset;
}

-(void)scrollViewDidScroll:(UIScrollView *)scrollView {
    if (scrollView.contentOffset.y<pointNow.y) {
        DLog(@"down");
    } else if (scrollView.contentOffset.y>pointNow.y) {
        DLog(@"up");
    }
}

回答2:

Use the methods from UIScrolViewDelegate's protocol. You can find the documentation here.