自定义 BarButtonItem 项：在右上角添加红点，Swift 4 IOS

Question

我想在UIbarButtonItem 的右上角添加/设置未读标志为红点，请参阅附图

我应该怎么做才能在条形按钮项目上添加/设置红点？ 一旦用户点击项目然后我想删除红点。

Answer 1

UIButton 子类

好的，让我们开始创建自定义UIButton 子类

class ButtonWithBadge: UIButton {
}

现在让我们创建UIView 来代表红点

let badgeView: UIView = {
    let view = UIView()
    view.layer.cornerRadius = 3
    view.backgroundColor = .red
    return view
}()

然后为这个子类覆盖init并在里面添加这个badgeView到你的按钮的右上角：设置它的约束（右和上等于按钮的锚点，宽度和高度是badgeView的cornerRadius的两倍值）

override init(frame: CGRect) {
    super.init(frame: frame)

    addSubview(badgeView)
    badgeView.translatesAutoresizingMaskIntoConstraints = false
    NSLayoutConstraint.activate([
        badgeView.rightAnchor.constraint(equalTo: rightAnchor, constant: 3),
        badgeView.topAnchor.constraint(equalTo: topAnchor, constant: 3),
        badgeView.heightAnchor.constraint(equalToConstant: badgeView.layer.cornerRadius*2),
        badgeView.widthAnchor.constraint(equalToConstant: badgeView.layer.cornerRadius*2)
    ])
}

required init?(coder aDecoder: NSCoder) {
    fatalError("init(coder:) has not been implemented")
}

接下来创建代表按钮当前状态的变量：

var isRead: Bool = false

现在让我们创建一些方法，根据isRead 的值隐藏或取消隐藏badgeView

func setBadge() {
    badgeView.isHidden = isRead
}

现在我们有了函数，对吧？所以让我们在init 的末尾和isRead 变量的didSet 中调用这个函数

class ButtonWithProperty: UIButton {

var isRead: Bool = false {
    didSet {
        setBadge()
    }
}

override init(frame: CGRect) {
    ...
    setBadge()
}

添加到 ViewController

首先为按钮和视图创建变量

lazy var barButton: ButtonWithProperty = {
    let button = ButtonWithProperty()
    ... // set color, title, target, etc.
    return button
}()

现在例如在viewDidLoad 中添加这个barButton 到UINavigationBar 并按照你想要的方式放置它：

override func viewDidLoad() {
    super.viewDidLoad()
    ...
    guard let navigationBar = self.navigationController?.navigationBar else { return }

    navigationBar.addSubview(barButton)
    barButton.translatesAutoresizingMaskIntoConstraints = false
    NSLayoutConstraint.activate([
        barButton.rightAnchor.constraint(equalTo: navigationBar.rightAnchor, constant: -20),
        barButton.bottomAnchor.constraint(equalTo: navigationBar.bottomAnchor, constant: -6)
    ])

}

现在，当您需要时，您可以轻松更改barButton 的isRead 变量，红点消失或出现

barButton.isRead = true

---

class ButtonWithProperty: UIButton {

    var isRead: Bool = false {
        didSet {
            setBadge()
        }
    }

    lazy var badgeView: UIView = {
        let view = UIView()
        view.layer.cornerRadius = 3
        view.backgroundColor = .red
        return view
    }()

    override init(frame: CGRect) {
        super.init(frame: frame)

        addSubview(badgeView)
        badgeView.translatesAutoresizingMaskIntoConstraints = false
        NSLayoutConstraint.activate([
            badgeView.rightAnchor.constraint(equalTo: rightAnchor, constant: 3),
            badgeView.topAnchor.constraint(equalTo: topAnchor, constant: 3),
            badgeView.heightAnchor.constraint(equalToConstant: badgeView.layer.cornerRadius*2),
            badgeView.widthAnchor.constraint(equalToConstant: badgeView.layer.cornerRadius*2)
        ])

        setBadge()
    }

    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

    func setBadge() {
        badgeView.isHidden = isRead
    }

}

ViewController 内部：

class ViewController: UIViewController {

    lazy var barButton: ButtonWithProperty = {
        let button = ButtonWithProperty()
        ... // color, title, target, etc.
        return button
    }()

    ...

    override func viewDidLoad() {
        super.viewDidLoad()
        ...
        guard let navigationBar = self.navigationController?.navigationBar else { return }

        navigationBar.addSubview(barButton)
        barButton.translatesAutoresizingMaskIntoConstraints = false
        NSLayoutConstraint.activate([
            barButton.rightAnchor.constraint(equalTo: navigationBar.rightAnchor, constant: -20),
            barButton.bottomAnchor.constraint(equalTo: navigationBar.bottomAnchor, constant: -6)
        ])

    }
    ...
}

Answer 2

我已经编写了一个自定义栏按钮类来处理这个问题，我使用CAShapeLayer 在UIBarButtonItem 上绘制一个点。

// Custom Bar button
class CustomBarButton: UIBarButtonItem
{
    // Unread Mark
    private var unreadMark: CAShapeLayer?

    // Keep track of unread status
    var hasUnread: Bool = false
    {
        didSet
        {
            setUnread(hasUnread: hasUnread)
        }
    }

    // Toggles unread status
    private func setUnread(hasUnread: Bool)
    {
        if hasUnread
        {
            unreadMark            = CAShapeLayer();
            unreadMark?.path      = UIBezierPath(ovalIn: CGRect(x: (self.customView?.frame.width ?? 0) - 10, y: 5, width: 5, height: 5)).cgPath;
            unreadMark?.fillColor = UIColor.red.cgColor
            self.customView?.layer.addSublayer(unreadMark!)
        }
        else
        {
            unreadMark?.removeFromSuperlayer()
        }

    }
}

栏按钮项没有可用的图层属性，因此您需要使用自定义视图创建UIBarButtonItem：

// Bar button property
var barButton:CustomBarButton!

// Initialisation
button       = UIButton(type: .custom)
button.frame = CGRect(x: 0, y: 0, width: 70, height: 40)
button.setTitle("Right", for: .normal)
button.setTitleColor(UIColor.green, for: .normal)

// Bar button
barButton = CustomBarButton(customView: button)
button.addTarget(self, action: #selector(toggleStatus(sender:)), for: UIControl.Event.touchUpInside)

// Flexible space (Optional)
let flexibleSpace = UIBarButtonItem(barButtonSystemItem: .flexibleSpace, target: nil, action: nil)
toolBar.items     = [flexibleSpace, barButton]

在IBAction 中，您可以使用hasUnread 属性切换状态：

@objc func toggleStatus(sender: AnyObject)
{
    barButton.hasUnread = !barButton.hasUnread
}

它看起来像：