Show tab bar after its hidden

Question

Is there any way to show a tab bar after it has been hidden?

Got a tabbar-nav structure. For one of the tabs, I need to hide the tab bar for its 2nd and 3rd level view. But at the same time I will need to show its 1st and 4th view.

The sample code from Elements isn't really applicable here I think.

Answer 1

I've found quite a good pragmatic solution to this problem - make the UITabBarController's view larger than it needs to be, so that the actual UITabBar is clipped by the screen.

Assuming that the tab bar view normally fills its superview, this sort of thing should work:

CGRect frame = self.tabBarController.view.superview.frame;
if (isHidden)
{
    CGFloat offset = self.tabBarController.tabBar.frame.size.height;
    frame.size.height += offset;
}
self.tabBarController.view.frame = frame;

The tab bar is still showing, but it's off the bottom of the screen, so appears to have been hidden.

It might have performance implications if it causes extra clipping, but so far, it seems to work.

Answer 2

The UIViewControllers that are pushed onto the navigation stack can do the something like the following:

- (void)viewWillAppear:(BOOL)animated {
    self.tabBarController.tabBar.hidden = NO; // Or YES as desired.
}

EDIT: Added additional code below to deal with the frame. Don't think I particular recommend this idea since it relies on the internal default view structure of a UITabBarController.

Define the following category on UITabBarController:

@interface UITabBarController (Extras)
- (void)showTabBar:(BOOL)show;
@end

@implementation UITabBarController (Extras)
- (void)showTabBar:(BOOL)show {
    UITabBar* tabBar = self.tabBar;
    if (show != tabBar.hidden)
        return;
    // This relies on the fact that the content view is the first subview
    // in a UITabBarController's normal view, and so is fragile in the face
    // of updates to UIKit.
    UIView* subview = [self.view.subviews objectAtIndex:0];
    CGRect frame = subview.frame;
    if (show) {
        frame.size.height -= tabBar.frame.size.height;
    } else {
        frame.size.height += tabBar.frame.size.height;
    }
    subview.frame = frame;
    tabBar.hidden = !show;
}
@end

Then, instead of using the tabBar.hidden change I originally suggested, do the following:

- (void)viewWillAppear:(BOOL)animated {
    [super viewWillAppear:animated];
    [self.tabBarController showTabBar:NO];
}

Obviously making sure that the implementation has included the category definition so that 'showTabBar' is known.