模仿iOS 7 Safari导航栏

Question

In iOS7 the navigationBar in Safari automatically shrinks when scrolling. So does the navigationBar in Facebook, even to a point where it completely vanishes.

How would you implement this behavior yourself? I guess you would also have to dynamically adjust the contentOffset and I guess that would also collide with the default Refresh Control, wouldn't it?

Answer 1

That's not right way of doing this, but it worked for me. I created category on UINavigationBar and overrode sizeThatFits: there like this:

- (CGSize)sizeThatFits:(CGSize)size
{
    CGSize cSize = self.frame.size;
    BOOL isPortrait = UIInterfaceOrientationIsPortrait([[UIApplication sharedApplication] statusBarOrientation]);
    CGFloat originalHeight = isPortrait ? 44: 32;
    cSize.height = self.tag > 0 ? originalHeight / 2 : originalHeight;
    return cSize;
}

Then when I need to shrink navigation bar (in scroll view's delegate methods):

CGRect navBarFrame = self.navigationController.navigationBar.frame;
BOOL isPortrait = UIInterfaceOrientationIsPortrait(self.interfaceOrientation);
CGFloat originalHeight = isPortrait ? 44: 32;
navBarFrame.size.height = expand ? originalHeight : originalHeight / 2;
self.navigationController.navigationBar.tag = expand ? 0 : 1;
[UIView animateWithDuration:0.25 animations:^{
    self.navigationController.navigationBar.frame = navBarFrame;
    [self.navigationController.view setNeedsLayout];
}

Also, you may want to hide navigation items (like UIBarButtonItems) inside animation.