The Mysterious Case of the Status Bar

All I wanted was two things for my status bar:

  • I wanted it to have white text by default as it was going to be on a dark background
  • I wanted to be able to hide it temporarily every now and again.

Straightforward right?

Not so much… Let’s take a look at the case.

So if you hunt around, there are so many ways to manipulate the status bar, let’s take a look at some:

General Settings of your Target

In the General tab for the preferences for your project’s target, you’ll find two fields that adjust the default behaviour of your status bar :

  • Status Bar Style – choose between Light (i.e. light text) or Default (i.e. dark text)
  • Hide status bar – a checkbox.

TargetSettings.png

These fields are derived from the info plist, which would be an alternative approach for adjusting these fields:

Info plist fields

If you’re using info.plist to adjust the default behaviour of your status bar, you’ll want to add rows for:

  • Status bar is initially hidden (UIStatusBarHidden) – Choose from YES or NO.
  • Status bar style (UIStatusBarStyle). Choose from either:
    • default (UIStatusBarStyleDefault)
    • light (UIStatusBarStyleLightContent)

Ignore that Xcode wants you to choose between Opaque black style and Transparent black style (alpha of 0.5). These are deprecated styles, it appears as though no-one told the property list editor that yet.

InfoPlistSettings.png

You may have noticed I have another status bar related row set up in the info.plist – another Boolean property called View controller-based status bar appearance – I’ll come back to this one in a moment.

So they are the ways to set up the defaults for the status bar style and whether it is hidden or not.

But how about if you want to temporarily change these defaults?

If you look around the internets, you’ll see two alternative solutions mentioned:

Set properties on the AppDelegate

Some will suggest you to set properties on the AppDelegate:

UIApplication.shared.statusBarStyle = .default //Set Style
UIApplication.shared.isStatusBarHidden = false //Set if hidden

These could be set for example in the didFinishLaunchingWithOptions method of your app’s AppDelegate, or anywhere you like really – for example, if you wanted to change this temporarily for a view controller you could call this in the viewDidAppear and viewDidDisappear methods.

Sounds great, right? Just call a method to update the status bar, easy.

Oh wait, sorry. I forgot to mention – the isStatusBarHidden and statusBarStyle properties were deprecated in iOS 9. Bah!

Screenshot 2018-08-23 13.14.50.png

Let’s take a look at the view controller properties that Xcode are suggesting:

Override properties in your view controller classes

Within your view controller classes, you can override the prefersStatusBarHidden and preferredStatusBarStyle properties:

override var prefersStatusBarHidden: Bool {
  return true
}
override var preferredStatusBarStyle: UIStatusBarStyle {
  return .lightContent
}

These methods return values by default (prefersStatusBarHidden = false, preferredStatusBarStyle = .default), so if you change either of these default values, when the user navigates to another view controller, if the new view controller doesn’t have its own implementation of these methods, it will revert to these defaults. This is a difference in behavior to setting properties on the appdelegate, which changes them for the duration of your app, well, at least until you specifically request they change again.

Changing mid view controller

By the way, you can use these properties to make this change mid view controller too. Just set up a variable, let’s call it statusBarHidden, to contain the current preference for the status bar.
We could then return this variable in the view controller property prefersStatusBarHidden:

var statusBarHidden = true
override var prefersStatusBarHidden: Bool {
  return statusBarHidden
}

Now if we change the statusBarHidden property, nothing will happen yet. We need to tell the system that we want the status bar to change. We can do this in a property observer:

var statusBarHidden = true {
  didSet(newValue) {
    setNeedsStatusBarAppearanceUpdate()
  }
}

Now we should be able to change the statusBarHidden property, and the status bar will automatically update. For example, we could have a button that toggles the status bar, connected to an IBAction:

@IBAction func toggleStatusBar(_ sender: Any) {
  statusBarHidden.toggle()
  //If you're pre Swift 4.2, use: statusBarHidden = !statusBarHidden
}

What do we have so far?

So, let’s summarize what we’ve got:

  • General Settings of your Target / Info plist fields
  • Set properties on the AppDelegate (deprecated, remember)
  • Override properties in your view controller classes

Here’s the stinger in the tail. Remember that View controller-based status bar appearance property we saw in the info plist file? Which options are available to us, depends on what we choose in this field:

If we have View controller-based status bar appearance set to NO, we can make a change to the default status bar in the general settings or info plist. We could also set properties on the AppDelegate, but don’t forget, that property is deprecated.

If we have View controller-based status bar appearance set to YES, we can override properties in our view controller classes.

Back to the problem…

Remember my original problem?

  • “…white text by default…” – the obvious way to do this would be change defaults in General Settings / Info.plist
  • “…hide it temporarily…” – the obvious way to do this would be simply to override properties in a view controller class.

Only problem is, these two solutions are mutually exclusive, I can’t set View controller-based status bar appearance to both NO and YES… Setting properties on AppDelegate would have been a good solution to this problem, but this technique is deprecated.

Which leaves me with the only solution of setting the style of the status bar on each view controller. A bit of a pain!

You could set up a subclass of UIViewController that manages this for you, and then every ViewController in your project would then have to implement this class…

class UIViewControllerWithLightStatusBar:UIViewController {
  override var preferredStatusBarStyle: UIStatusBarStyle {
    return UIStatusBarStyle.lightContent
  }
}
...
class ViewController: UIViewControllerWithLightStatusBar {
...

But this is still an inconvenience and feels a little hacky. If anyone knows of a reliable and safe way to change the status bar behavior project-wide while having View controller-based status bar appearance set to YES, I’m interested to hear it!

Navigation Controllers

I’m afraid we’re not done on the mysterious case of status bars – embed your view controller in a navigation controller, and if you have View controller-based status bar appearance set to YES, suddenly the navigation controller now takes over control of the style of the status bar, and your view controller’s preferredStatusBarStyle property will be ignored.

If you want to adjust the style of the status bar in a navigation controller, you’ll need to do this in the navigation bar’s style property, either in code, eg:

override func viewDidAppear(_ animated: Bool) {
  navigationController?.navigationBar.barStyle = .black
}

Or in the storyboard:
Screenshot 2018-08-23 13.40.18.png

To make things ultra-confusing, if you want, for example, that your status bar has white text, view controllers not embedded in a navigation controller will need to request the .lightContent style (i.e. light colored writing), and view controllers embedded in a navigation controller will need to request the .black style (i.e. a black colored nav bar).

Don’t forget, if you have View controller-based status bar appearance set to NO, any changes you make to the navigation bar style will be ignored.

In summary

For View controller-based status bar appearance = NO:

  • General Settings of your Target / Info.plist fields
  • Set properties on the AppDelegate (deprecated, remember)

For View controller-based status bar appearance = YES:

  • Override properties in your view controller classes
  • Set style of navigation controllers / navigation bars.

So, mystery solved… sort of!  If you ask me, it’s all a bit unnecessarily complicated, but there it is, the status of the status bar!

iOS development with Swift - book: https://manning.com/books/ios-development-with-swift video course: https://www.manning.com/livevideo/ios-development-with-swift-lv

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