Question

我有一个简单的PageViewController，我想根据从页面0滚动到页面1的百分比来更改顶部约束，即它开始于从超级视图顶部固定80像素，但是当我移至页面1时，我想要将其减少到40像素。

我已经将UIPageViewController子类化以公开滚动委托。我已经在一个简单的应用程序项目中进行了尝试，并获得了相同的结果，就像我尝试滑动时遇到的陪练经历，似乎与在调整约束的同时为pageviewcontroller设置动画感到困惑。

import UIKit

enum ScrollDirection {
case left
case right
}

class PSPageViewController: UIPageViewController, UIScrollViewDelegate {
weak var scrollDelegate: ScrollDelegate?
func scrollMoved(_ progress : CGFloat, _ direction: ScrollDirection)
{
    if let scrollDelegate = scrollDelegate
    {
        scrollDelegate.PageViewScrolledDelegate(progress, direction)
    }
}

override func viewDidLoad() {
    super.viewDidLoad()
    for subView in view.subviews {
        if let scrollView = subView as? UIScrollView {
            scrollView.delegate = self
        }
    }

    // Do any additional setup after loading the view.
}



var lastOffset : CGFloat = 0

func scrollViewDidScroll(_ scrollView: UIScrollView) {

    let point = scrollView.contentOffset

    var direction = ScrollDirection.right
    if (point.x < lastOffset)
    {
        direction = .left
    }
    lastOffset = point.x

    //         NSLog("x: %f", point.x)
    //         NSLog("width: %f", view.frame.size.width)

    var percentComplete: CGFloat
    percentComplete = fabs(point.x - view.frame.size.width)/view.frame.size.width
    self.scrollMoved(percentComplete, direction)

}




}

当我启动PVC时，我使用此代码（使用示例项目）

self.pageViewController = PSPageViewController(transitionStyle: .scroll, navigationOrientation: .horizontal, options: nil)
    self.pageViewController!.delegate = self

    self.pageViewController!.scrollDelegate = self

然后使用我自己的代理人

func PageViewScrolledDelegate(_ progress: CGFloat, _ direction: ScrollDirection) {
    topConstraint.constant = 80 - (40 * progress)
    print(progress)
}

有人遇到过同样的问题吗？如果可以，我该如何解决？

感谢您的所有帮助

UIPageViewController和基于滚动百分比的更改约束

0 个答案: