Odd behavior from UITabBar where background color only shows for one tab

问题

I am using Swift 3 and I researched various methods to set the backgroundColor color of a UITabBar. The most simple method was to change the property in the didFinishLaunchingWithOptions of the AppDelegate. When I tried to do this, the UITabBar launches with the standard color, which is not my intended result.

However, when I go to the next tab, the UITabBar color gets changed to my intended color.

Following this, I tried to subclass my UITabBarController and I tried to set the background colors in both the viewDidLoad and in the viewDidLayoutSubViews. All three of these attempts exhibited the exact same behavior - which was the UITabBar launched with the standard color, and only changed colors when I tabbed to the next tab.

Here is my code:

App Delegate

func application(_ application: UIApplication, 
    didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) 
    -> Bool {
        UITabBar.appearance().backgroundColor = UIColor.red
        return true
}

viewDidLoad

override func viewDidLoad() {
    super.viewDidLoad()
    self.tabBar.backgroundColor = UIColor.red
}

viewDidLayoutSubviews

override func viewDidLayoutSubviews() {
    self.tabBar.backgroundColor = UIColor.red
}

My questions are the following:

1) Can I eliminate this as being a constraint issue? I didn't modify or set any constraints for the UITabBar

2) I have a launch screen where the user selects acknowledges something and then they are segued to the UITabBarController. Could this be part of the issue?

回答1:

The basic way to change to a tab bar's color is not to set its backgroundColor as you are doing, but rather to set its barTintColor. (For more sophisticated control, use a colored backgroundImage.)

回答2:

Putting this in my app delegate gets me a tab bar that's tinted red.

func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {

    window = UIWindow(frame: UIScreen.main.bounds)
    let tabBarVC = UITabBarController()
    tabBarVC.viewControllers = [FirstViewController(), SecondViewController()]
    tabBarVC.tabBar.backgroundColor = UIColor.red
    window?.rootViewController = tabBarVC
    window?.makeKeyAndVisible()

    return true
}

来源：https://stackoverflow.com/questions/41052346/odd-behavior-from-uitabbar-where-background-color-only-shows-for-one-tab

标签

ios

swift3

uitabbarcontroller

uitabbar