Imitate Facebook hide/show expanding/contracting Navigation Bar

Question

The solution given by @peerless is a great start, but it only kicks off an animation whenever dragging begins, without considering the speed of the scroll. This results in a choppier experience than you get in the Facebook app. To match Facebook's behavior, we need to:

• hide/show the navbar at a rate that is proportional to the rate of the drag
• kick off an animation to completely hide the bar if scrolling stops when the bar is partially hidden
• fade the navbar's items as the bar shrinks.

First, you'll need the following property:

@property (nonatomic) CGFloat previousScrollViewYOffset;

And here are the UIScrollViewDelegate methods:

- (void)scrollViewDidScroll:(UIScrollView *)scrollView
{
    CGRect frame = self.navigationController.navigationBar.frame;
    CGFloat size = frame.size.height - 21;
    CGFloat framePercentageHidden = ((20 - frame.origin.y) / (frame.size.height - 1));
    CGFloat scrollOffset = scrollView.contentOffset.y;
    CGFloat scrollDiff = scrollOffset - self.previousScrollViewYOffset;
    CGFloat scrollHeight = scrollView.frame.size.height;
    CGFloat scrollContentSizeHeight = scrollView.contentSize.height + scrollView.contentInset.bottom;

    if (scrollOffset <= -scrollView.contentInset.top) {
        frame.origin.y = 20;
    } else if ((scrollOffset + scrollHeight) >= scrollContentSizeHeight) {
        frame.origin.y = -size;
    } else {
        frame.origin.y = MIN(20, MAX(-size, frame.origin.y - scrollDiff));
    }

    [self.navigationController.navigationBar setFrame:frame];
    [self updateBarButtonItems:(1 - framePercentageHidden)];
    self.previousScrollViewYOffset = scrollOffset;
}

- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView
{
    [self stoppedScrolling];
}

- (void)scrollViewDidEndDragging:(UIScrollView *)scrollView 
                  willDecelerate:(BOOL)decelerate
{
    if (!decelerate) {
        [self stoppedScrolling];
    }
}

You'll also need these helper methods:

- (void)stoppedScrolling
{
    CGRect frame = self.navigationController.navigationBar.frame;
    if (frame.origin.y < 20) {
        [self animateNavBarTo:-(frame.size.height - 21)];
    }
}

- (void)updateBarButtonItems:(CGFloat)alpha
{
    [self.navigationItem.leftBarButtonItems enumerateObjectsUsingBlock:^(UIBarButtonItem* item, NSUInteger i, BOOL *stop) {
        item.customView.alpha = alpha;
    }];
    [self.navigationItem.rightBarButtonItems enumerateObjectsUsingBlock:^(UIBarButtonItem* item, NSUInteger i, BOOL *stop) {
        item.customView.alpha = alpha;
    }];
    self.navigationItem.titleView.alpha = alpha;
    self.navigationController.navigationBar.tintColor = [self.navigationController.navigationBar.tintColor colorWithAlphaComponent:alpha];
}

- (void)animateNavBarTo:(CGFloat)y
{
    [UIView animateWithDuration:0.2 animations:^{
        CGRect frame = self.navigationController.navigationBar.frame;
        CGFloat alpha = (frame.origin.y >= y ? 0 : 1);
        frame.origin.y = y;
        [self.navigationController.navigationBar setFrame:frame];
        [self updateBarButtonItems:alpha];
    }];
}

For a slightly different behavior, replace the line that re-positions the bar when scrolling (the else block in scrollViewDidScroll) with this one:

frame.origin.y = MIN(20, 
                     MAX(-size, frame.origin.y - 
                               (frame.size.height * (scrollDiff / scrollHeight))));

This positions the bar based on the last scroll percentage, instead of an absolute amount, which results in a slower fade. The original behavior is more Facebook-like, but I like this one, too.

Note: This solution is iOS 7+ only. Be sure to add the necessary checks if you're supporting older versions of iOS.

EDIT: Only for iOS 8 and above.

You can try use

self.navigationController.hidesBarsOnSwipe = YES;

Works for me.

If your coding in swift you have to use this way (from https://stackoverflow.com/a/27662702/2283308)

navigationController?.hidesBarsOnSwipe = true

Here is one more implementation: TLYShyNavBar v1.0.0 released!

I decided to make my own after trying the solutions provided, and to me, they were either performing poorly, had a a high barrier of entry and boiler plate code, or lacked the extension view beneath the navbar. To use this component, all you have to do is:

self.shyNavBarManager.scrollView = self.scrollView;

Oh, and it is battle tested in our own app.

You can have a look at my GTScrollNavigationBar. I have subclassed UINavigationBar to make it scroll based on the scrolling of a UIScrollView.

Note: If you have an OPAQUE navigation bar, the scrollview must EXPAND as the navigation bar gets HIDDEN. This is exactly what GTScrollNavigationBar does. (Just as in for example Safari on iOS.)