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缩放的UIPageControl点未居中

uipagecontrol uikit swift ios

CÅur Gustavo Armenta · 技术社区 · 6 年前

我对UIPageControl进行了子类化,以使其当前点更大。

class CustomPageControl: UIPageControl {
    override var currentPage: Int {
        didSet {
            updateDots()
        }
    }

    func updateDots() {
        let currentDot = subviews[currentPage]
        let largeScaling = CGAffineTransform(scaleX: 3, y: 3)

        subviews.forEach {
            // apply the large scale of newly selected dot
            // restore the normal scale of previously selected dot
            $0.transform = $0 == currentDot ? largeScaling : .identity
        }
    }
}

我试过(在iOS 12上):

更改 frame center 属于 currentDot 没有效果。
translatedBy(x: CGFloat, y: CGFloat) 没有效果。

更改约束 like here

currentDot.translatesAutoresizingMaskIntoConstraints = false
currentDot.centerYAnchor.constraint(equalTo: self.centerYAnchor, constant: 0)
currentDot.centerXAnchor.constraint(equalTo: self.centerXAnchor, constant: 0)

0 回复 | 直到 6 年前

CÅur Gustavo Armenta 5 年前

我终于重写了 全部的 子视图由我自己约束。

// https://stackoverflow.com/a/55063316/1033581
class DefaultPageControl: UIPageControl {

    override var currentPage: Int {
        didSet {
            updateDots()
        }
    }

    override func sendAction(_ action: Selector, to target: Any?, for event: UIEvent?) {
        super.sendAction(action, to: target, for: event)
        updateDots()
    }

    private func updateDots() {
        let currentDot = subviews[currentPage]
        let largeScaling = CGAffineTransform(scaleX: 3.0, y: 3.0)
        let smallScaling = CGAffineTransform(scaleX: 1.0, y: 1.0)

        subviews.forEach {
            // Apply the large scale of newly selected dot.
            // Restore the small scale of previously selected dot.
            $0.transform = $0 == currentDot ? largeScaling : smallScaling
        }
    }

    override func updateConstraints() {
        super.updateConstraints()
        // We rewrite all the constraints
        rewriteConstraints()
    }

    private func rewriteConstraints() {
        let systemDotSize: CGFloat = 7.0
        let systemDotDistance: CGFloat = 16.0

        let halfCount = CGFloat(subviews.count) / 2
        subviews.enumerated().forEach {
            let dot = $0.element
            dot.translatesAutoresizingMaskIntoConstraints = false
            NSLayoutConstraint.deactivate(dot.constraints)
            NSLayoutConstraint.activate([
                dot.widthAnchor.constraint(equalToConstant: systemDotSize),
                dot.heightAnchor.constraint(equalToConstant: systemDotSize),
                dot.centerYAnchor.constraint(equalTo: centerYAnchor, constant: 0),
                dot.centerXAnchor.constraint(equalTo: centerXAnchor, constant: systemDotDistance * (CGFloat($0.offset) - halfCount))
            ])
        }
    }
}

Finetuning-mg 5 年前

我尝试了由 CÅur 在Swift 5和Xcode 11中,它可以很好地处理一些注释:

IB/Storyboard中的PageControl元素必须使用约束进行定位。
点稍微偏离中心,但可以通过将最后一个约束的常数更改为 systemDotDistance * ( CGFloat($0.offset) - (halfCount - 0.5))
如果 updateConstraints 覆盖从未调用,您可能需要调用 self.view.setNeedsUpdateConstraints()