ios - Swift - 如何在设置后更改 UIButton 的 NSMutableAttributedString 的颜色

Question

我有 2 个 UIButtons，它们的 titles 和 colors 最初是使用 NSMutableAttributedString 设置的。正文是2 lines of text

我有一个自定义的 UISegmentedControl，当切换段时，我只需要更改按钮的颜色。我现在这样做的方式是，颜色确实发生了变化，但是当发生这种情况时会出现难看的闪烁，因为实际文本会再次设置。我只需要颜色的平滑过渡

var selectedSegmentIndex = 0 {
    didSet {

        layoutIfNeeded()
        UIView.animate(withDuration: 0.1) {
            self.setTextForFollowersButton()
            self.setTextForFollowingButton()
            self.layoutIfNeeded()
        }
    }
}

如何只更改按钮的 NSMutableAttributedString 的颜色？

按钮代码:

var numOfFollowers = 0 {
    didSet {
        setTextForFollowersButton()
    }
}
var numOfFollowing = 0 {
    didSet {
        setTextForFollowingButton()
    }
}

lazy var followersButton: UIButton = {
    let button = UIButton.init(type: .system)
    // ...
    return button
}()

lazy var followingButton: UIButton = {
    let button = UIButton.init(type: .system)
    //...
    return button
}()

func setTextForFollowersButton() {

    let button = self.followersButton
    let buttonText = "Following\n\(String(numOfFollowing))" as NSString
    // other code for 2 lines of text

    var color = UIColor.blue

    if selectedSegmentIndex == 0 {
        color = UIColor.blue
    } else {
        color = UIColor.gray
    }

    let attrString1 = NSMutableAttributedString(string: substring1,
                                                attributes: [NSMutableAttributedString.Key.font:
                                                    UIFont.boldSystemFont(ofSize: 16),
                                                             NSMutableAttributedString.Key.foregroundColor: color])

    let attrString2 = NSMutableAttributedString(string: substring2,
                                                attributes: [NSMutableAttributedString.Key.font:
                                                    UIFont.boldSystemFont(ofSize: 14),
                                                             NSMutableAttributedString.Key.foregroundColor: color])

    attrString1.append(attrString2)
    button.setAttributedTitle(attrString1, for: [])
}

func setTextForFollowingButton() {

    let button = self.followingButton

    let buttonText = "Following\n\(String(numOfFollowing))" as NSString
    // other code for 2 lines of text

    var color = UIColor.blue

    if selectedSegmentIndex == 0 {
        color = UIColor.gray
    } else {
        color = UIColor.blue
    }

    let attrString1 = NSMutableAttributedString(string: substring1,
                                                attributes: [NSMutableAttributedString.Key.font:
                                                    UIFont.boldSystemFont(ofSize: 16),
                                                             NSMutableAttributedString.Key.foregroundColor: color])

    let attrString2 = NSMutableAttributedString(string: substring2,
                                                attributes: [NSMutableAttributedString.Key.font:
                                                    UIFont.boldSystemFont(ofSize: 14),
                                                             NSMutableAttributedString.Key.foregroundColor: color])

    attrString1.append(attrString2)
    button.setAttributedTitle(attrString1, for: [])
}

Answer 1

您应该在 DispatchQueue.main.async {} 中插入 UIView.animate 函数以实现平滑过渡。始终建议在主线程上异步制作任何类型的 UI 动画。