ios 11 UITabBar UITabBarItem positioning issue

Question

I have built my app using new Xcode 9 beta for ios 11. I have found an issue with UITabBar where items are spread through the UITabBar and title is right aligned to the image. I have tried changing the code to get it to work but still not successful.

ios 10+

ios 11

I could change the position of title using tabBarItem.titlePositionAdjustment But that is not my requirement as it should automatically come bellow the image itself. I tried setting tabbar.itemPositioning to UITabBarItemPositioningCentered and also tried changing itemSpacing and width, but still did not work. Can someone help me understand why this happens and how to fix this? I want it to like ios 10+ version and images are taken from the left most corner of an iPad.

Answer 1

I am maintaining a large iPad app written mostly in Objective-C that has survived several iOS releases. I ran into the situation where I needed the pre-iOS 11 tab bar appearance (with the icons above the titles instead of next to them) for a couple tab bars. My solution was to create a subclass of UITabBar that overrides the traitCollection method so that it always returns a horizontally-compact trait collection. This causes iOS 11 to display the titles below the icons for all of the tab bar buttons.

In order to use this, set the custom class of the tab bars in the storyboard to this new subclass and change any outlets in the code that point to the tab bars to be of this new type (don't forget to import the header file below).

The .h file is pretty much empty in this case:

//
//  MyTabBar.h
//

#import <UIKit/UIKit.h>

@interface MyTabBar : UITabBar

@end

Here is the .m file with the implementation of the traitCollection method:

//
//  MyTabBar.m
//

#import "MyTabBar.h"

@implementation MyTabBar

// In iOS 11, UITabBarItem's have the title to the right of the icon in horizontally regular environments
// (i.e. the iPad).  In order to keep the title below the icon, it was necessary to subclass UITabBar and override
// traitCollection to make it horizontally compact.

- (UITraitCollection *)traitCollection {
    return [UITraitCollection traitCollectionWithHorizontalSizeClass:UIUserInterfaceSizeClassCompact];
}

@end

Answer 2

Based on John C's answer, here is the Swift 3 version that can be used programmatically without need for Storyboard or subclassing:

extension UITabBar {
    // Workaround for iOS 11's new UITabBar behavior where on iPad, the UITabBar inside
    // the Master view controller shows the UITabBarItem icon next to the text
    override open var traitCollection: UITraitCollection {
        if UIDevice.current.userInterfaceIdiom == .pad {
            return UITraitCollection(horizontalSizeClass: .compact)
        }
        return super.traitCollection
    }
}

Answer 3

To avoid messing up any other traits is it not better to combine with the superclasses:

- (UITraitCollection *)traitCollection
{
  UITraitCollection *curr = [super traitCollection];
  UITraitCollection *compact = [UITraitCollection  traitCollectionWithHorizontalSizeClass:UIUserInterfaceSizeClassCompact];

  return [UITraitCollection traitCollectionWithTraitsFromCollections:@[curr, compact]];
}