问题描述
我有一个类继承了UIPageViewController，该类包含4个控制器，我试图弄清楚如何在滚动到第二个视图控制器时更改按钮的颜色
按钮颜色只能在第一个控制器上改变
此代码几乎可以正常工作，但行为仅对第三个控制器而言并不正确，这意味着解决方案不正确。
如果有人可以帮忙，我将非常感激。谢谢
public func scrollViewDidScroll(_ scrollView: UIScrollView) {
let point = scrollView.contentOffset
let width = scrollView.frame.width
let percentComplete = abs(point.x - width) / width
let page = Int(round(percentComplete))
if percentComplete >= 0.5 {
if page == 1,currentIndex == 1 {
nextButton.backgroundColor = .red
} else {
nextButton.backgroundColor = .blue
}
print ("percentComplete: ",percentComplete,"page: ",page,"currentIndex: ",currentIndex,"point: ",point.x)
}
}
解决方法
即使您说要使用UIPageViewController，这也是使用UIScrollView的示例实现，您可能会发现它更易于管理：
class PagedScrollViewController: UIViewController,UIScrollViewDelegate {
let scrollView: UIScrollView = {
let v = UIScrollView()
v.isPagingEnabled = true
v.bounces = false
return v
}()
let pageControl: UIPageControl = {
let v = UIPageControl()
return v
}()
let stack: UIStackView = {
let v = UIStackView()
v.axis = .horizontal
v.distribution = .fillEqually
return v
}()
var pages: [UIViewController] = []
override func viewDidLoad() {
super.viewDidLoad()
scrollView.translatesAutoresizingMaskIntoConstraints = false
pageControl.translatesAutoresizingMaskIntoConstraints = false
stack.translatesAutoresizingMaskIntoConstraints = false
scrollView.addSubview(stack)
view.addSubview(scrollView)
view.addSubview(pageControl)
let g = view.safeAreaLayoutGuide
let svCLG = scrollView.contentLayoutGuide
let svFLG = scrollView.frameLayoutGuide
NSLayoutConstraint.activate([
scrollView.topAnchor.constraint(equalTo: g.topAnchor,constant: 20.0),scrollView.leadingAnchor.constraint(equalTo: g.leadingAnchor,scrollView.trailingAnchor.constraint(equalTo: g.trailingAnchor,constant: -20.0),scrollView.bottomAnchor.constraint(equalTo: g.bottomAnchor,constant: -80.0),stack.topAnchor.constraint(equalTo: svCLG.topAnchor,constant: 0.0),stack.leadingAnchor.constraint(equalTo: svCLG.leadingAnchor,stack.trailingAnchor.constraint(equalTo: svCLG.trailingAnchor,stack.bottomAnchor.constraint(equalTo: svCLG.bottomAnchor,stack.heightAnchor.constraint(equalTo: svFLG.heightAnchor,pageControl.topAnchor.constraint(equalTo: scrollView.bottomAnchor,constant: 8.0),pageControl.leadingAnchor.constraint(equalTo: scrollView.leadingAnchor),pageControl.trailingAnchor.constraint(equalTo: scrollView.trailingAnchor),])
// if we're loading "page" view controllers from Storyboard
/*
if let vc = storyboard?.instantiateViewController(withIdentifier: "psFirst") as? PSFirstViewController {
pages.append(vc)
}
if let vc = storyboard?.instantiateViewController(withIdentifier: "psSecond") as? PSSecondViewController {
pages.append(vc)
}
if let vc = storyboard?.instantiateViewController(withIdentifier: "psThird") as? PSThirdViewController {
pages.append(vc)
}
if let vc = storyboard?.instantiateViewController(withIdentifier: "psFourth") as? PSFourthViewController {
pages.append(vc)
}
pages.forEach { vc in
self.addChild(vc)
stack.addArrangedSubview(vc.view)
vc.view.widthAnchor.constraint(equalTo: scrollView.frameLayoutGuide.widthAnchor,constant: 0.0).isActive = true
vc.didMove(toParent: self)
}
*/
// for this example,// create 4 view controllers,with background colors
let colors: [UIColor] = [
.red,.brown,.blue,.magenta
]
colors.forEach { c in
let vc = BasePageController()
vc.view.backgroundColor = c
self.addChild(vc)
stack.addArrangedSubview(vc.view)
vc.view.widthAnchor.constraint(equalTo: scrollView.frameLayoutGuide.widthAnchor,constant: 0.0).isActive = true
vc.didMove(toParent: self)
pages.append(vc)
}
pageControl.numberOfPages = pages.count
scrollView.delegate = self
pageControl.addTarget(self,action: #selector(self.pgControlChange(_:)),for: .valueChanged)
}
var pgControlScroll: Bool = false
@objc func pgControlChange(_ sender: UIPageControl) {
pgControlScroll = true
let w = scrollView.frame.size.width
guard w != 0 else { return }
let x = scrollView.contentOffset.x
let cp = min(Int(round(x / w)),pages.count - 1)
let np = sender.currentPage
var r = CGRect.zero
if np > cp {
r = CGRect(x: w * CGFloat(np + 1) - 1.0,y: 0,width: 1,height: 1)
} else {
r = CGRect(x: w * CGFloat(np),height: 1)
}
scrollView.scrollRectToVisible(r,animated: true)
}
func scrollViewWillBeginDragging(_ scrollView: UIScrollView) {
pgControlScroll = false
}
func scrollViewDidScroll(_ scrollView: UIScrollView) {
let w = scrollView.frame.size.width
guard w != 0 else { return }
let x = scrollView.contentOffset.x
let pg = min(Int(round(x / w)),pages.count - 1)
let v = stack.arrangedSubviews[pg]
pageControl.backgroundColor = v.backgroundColor
if pgControlScroll { return }
pageControl.currentPage = pg
}
}
class BasePageController: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
// add a label at each corner
for (i,s) in ["top-left","top-right","bot-left","bot-right"].enumerated() {
let v = UILabel()
v.backgroundColor = UIColor(white: 0.8,alpha: 1.0)
v.translatesAutoresizingMaskIntoConstraints = false
v.text = s
view.addSubview(v)
let g = view.safeAreaLayoutGuide
switch i {
case 1:
v.topAnchor.constraint(equalTo: g.topAnchor,constant: 4.0).isActive = true
v.trailingAnchor.constraint(equalTo: g.trailingAnchor,constant: -4.0).isActive = true
case 2:
v.bottomAnchor.constraint(equalTo: g.bottomAnchor,constant: -4.0).isActive = true
v.leadingAnchor.constraint(equalTo: g.leadingAnchor,constant: 4.0).isActive = true
case 3:
v.bottomAnchor.constraint(equalTo: g.bottomAnchor,constant: -4.0).isActive = true
v.trailingAnchor.constraint(equalTo: g.trailingAnchor,constant: -4.0).isActive = true
default:
v.topAnchor.constraint(equalTo: g.topAnchor,constant: 4.0).isActive = true
v.leadingAnchor.constraint(equalTo: g.leadingAnchor,constant: 4.0).isActive = true
}
}
}
}
该代码添加了一个滚动视图，该视图占据了屏幕的大部分内容（带有一些填充，因此滚动视图的框架很明显），其下方为UIPageControl。
我们添加4个视图控制器作为子视图控制器，并将其视图添加到滚动视图的UIStackView中。
当您从“页面到页面”滚动时，页面控件将在您到达下一页/上一页的中途更新和更改背景颜色。
, UIPageViewController没有任何我知道的跟踪部分滚动的机制。它基于这样的假设，即页面视图控制器已经存在，并且只有在用户完成“页面翻转”之后，您才会收到通知。
它还支持页面卷曲样式的页面翻转和侧向滚动，这将使尝试破解解决方案变得更加复杂/脆弱。