ios - 模仿 iOS 7 Safari 导航栏

Question

在 iOS7 中，Safari 中的导航栏在滚动时会自动缩小。Facebook 中的导航栏也是如此，甚至到了完全消失的地步。

您将如何自己实施这种行为？我想您还必须动态调整 contentOffset 并且我想这也会与默认的刷新控件发生冲突，不是吗？

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.