设置界面TabBar中Review（favorite）图标缺失问题咨询

Hey there! Let's walk through some common causes and fixes for this weird TabBar icon issue—where the Review (favorite) icon disappears when you're on the Settings screen, but shows up again when you switch back to the Review screen. Here are my top troubleshooting steps:

• Check when you're assigning the TabBarItem icon
  A super common culprit is that you're only setting the tabBarItem.image and tabBarItem.selectedImage inside the Review view controller's lifecycle methods (like viewDidLoad or viewWillAppear). If the Review VC hasn't been initialized yet (which happens if you haven't navigated to it before), its TabBarItem won't have the icon set when you first land on Settings. Fix this by moving the TabBarItem configuration to your TabBarController's setup code, so all items are configured upfront, not just when their VC loads.

• Verify icon asset rendering & visibility
  If you're using asset catalogs, double-check the icon's rendering mode—if it's set to "Template Image" and the tint color matches the TabBar's background in the Settings screen, the icon will be invisible. Try setting the rendering mode to "Always Original" (via code: UIImage(named: "favorite")?.withRenderingMode(.alwaysOriginal)) or swap in a bright, high-contrast test icon to see if it shows up. Also confirm the asset name is spelled correctly everywhere (typos happen!).

• Look for code that modifies TabBar items
  Check if there's any code in your Settings view controller (or a parent coordinator) that's hiding, removing, or disabling the Review TabBarItem when you enter Settings. Common red flags include:

  // Accidental removal or hiding
  tabBar.items?.remove(at: reviewTabIndex)
  tabBar.items?[reviewTabIndex].isEnabled = false
  

  If you're using a custom TabBar library, make sure it's not overriding the item states incorrectly during screen transitions.

• Debug the view hierarchy
  When the icon is missing, use Xcode's Debug View Hierarchy tool to inspect the TabBar. Look for the Review TabBarItem's icon view—does it exist? Is its frame set to 0x0? Is it hidden (isHidden = true)? This can tell you if the icon is truly missing, or just not visible due to layout issues.

• Check lazy loading of view controllers
  If your TabBarController uses lazy loading for its view controllers, the Review VC might not be initialized until you first navigate to it. That means its TabBarItem isn't fully set up until then, causing the missing icon on initial Settings visits. Pre-initialize the Review VC when setting up the TabBarController to avoid this.

• Rule out state restoration quirks
  If you've enabled UIKit state restoration (via restorationIdentifier on your controllers), it might be saving a broken state of the TabBar. Try removing the restoration identifiers temporarily to see if the issue goes away.

内容的提问来源于stack exchange，提问作者ThinkGeek