iosswiftuiappearance

Why does UIButton Label ingnores appearance setting when contained in UITableView tableHeaderView?

I have created a simple UIViewController which contains a UITableView. When adding a tableHeaderView which includes a UIButton it seems not to be possible to change the button label using appearance settings. Other buttons outside the tableHeaderView are updated correctly.

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Here the button which was placed directly in the ViewControllers view is updated correctly while the appearance settings seem not to effect the button inside the tableHeaderView.

class ListViewController: UIViewController, UITableViewDelegate, UITableViewDataSource {
    @IBOutlet weak var tableHeaderView: UIView!
    @IBOutlet weak var tableView: UITableView!
    
    override func viewDidLoad() {
        UILabel.appearance(whenContainedInInstancesOf: [TestButton.self]).font = UIFont.systemFont(ofSize: 30)
        UILabel.appearance(whenContainedInInstancesOf: [TestButton.self]).textColor = .red
        
        super.viewDidLoad()
        tableView.register(UITableViewCell.self, forCellReuseIdentifier: "cell")
        tableView.tableHeaderView = tableHeaderView
    }
    
    ...
}

class TestButton: UIButton {}

There are now other appearance settings in the project which might explain this. Moving the appearance settings to some other place, e.g. application:didFinishLaunchingWithOptions does not change the problem.

Is this a bug or am I missing something?

Solution

  • That will likely not be a suitable approach.

    A UIButton does various things with its titleLabel - including changing the text color.

    Trying to use UILabel.appearance(...) will not override the normal behavior.

    You can see this by running your code as-is:

    This is the same reason why we use:

    button.setTitleColor(.red, for: .normal)

    instead of:

    button.titleLabel?.textColor = .red

    You probably want to configure those properties in your custom TestButton class. Here's the basics:

    class TestButton: UIButton {
    
    override init(frame: CGRect) {
        super.init(frame: frame)
        commonInit()
    }
    required init?(coder: NSCoder) {
        super.init(coder: coder)
        commonInit()
    }
    func commonInit() {
        setTitleColor(.red, for: .normal)
        setTitleColor(.lightGray, for: .highlighted)
        titleLabel?.font = UIFont.systemFont(ofSize: 30)
        backgroundColor = .systemBlue
        layer.cornerRadius = 6
    }
}