Navigation- & Toolbar not hidden when UIScrollView scrolls

Question

- (void)scrollViewDidScroll:(UIScrollView *)scrollView {
    lastOffset = scrollView.contentOffset;

    if (scrollView.contentOffset.y < lastOffset.y) {
        [self.navigationController setNavigationBarHidden:YES animated:YES];
        [self.navigationController setToolbarHidden:YES animated:YES];
    }
    else {
        [self.navigationController setNavigationBarHidden:NO animated:YES];
        [self.navigationController setToolbarHidden:NO animated:YES];
    }
}

What am I doing wrong? The UIScrollViewDelegate is already set in my header file.

score 4 · Accepted Answer · answered Aug 29 '12 at 19:11

4

You should move

lastOffset = scrollView.contentOffset;

to the end of the method, otherwise

scrollView.contentOffset.y < lastOffset.y

will never be true.

answered Aug 29 '12 at 19:11

Martin R

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why is the second line in your answer wrong? do you know where the error is? – filou Aug 29 '12 at 19:14
If you set `lastOffset = scrollView.contentOffset` then `scrollView.contentOffset.y` is equal to `lastOffset.y`. – Martin R Aug 29 '12 at 19:15
the bars should hide when the user scrolls down. how do I achieve that? – filou Aug 29 '12 at 19:17
Did you try what I suggested? Move the statement `lastOffset = scrollView.contentOffset` to the end of the method? – Martin R Aug 29 '12 at 19:19
yes, it's at the end now. But as you already said: `scrollView.contentOffset.y < lastOffset.y` is invalid. how can I fix that? this is my problem :) – filou Aug 29 '12 at 19:21
Where is `lastOffset` declared? – Martin R Aug 29 '12 at 19:22
it's just alloc'd in my header file. – filou Aug 29 '12 at 19:24
let us [continue this discussion in chat](http://chat.stackoverflow.com/rooms/15984/discussion-between-martin-r-and-sascha-wieland) – Martin R Aug 29 '12 at 19:25

score 1 · Answer 2 · answered Aug 29 '12 at 19:14

It's not hidden because every time code in else part is invoked. Suppose contentOffset = (100, 100) then you set last offset to equal contentOffset so if (scrollView.contentOffset.y < lastOffset.y) it will never be true. Put lastOffset = scrollView.contentOffset; on the end of scrollViewDidScroll method.

Navigation- & Toolbar not hidden when UIScrollView scrolls

2 Answers2