我有一个分页UIScrollView
,每个页面都填充了不同的视图控制器。在scrollview上方是一个UICollectionView
,充当菜单栏。滚动浏览滚动视图页面时,菜单栏会稍微移动一下。你可以从左边的gif看到。
将其委托设置为不同的类可以使一切正常工作,如左侧的gif所示。但是,将它们设置为同一个类会扰乱UICollectionView
s的行为。
如何将他们的代表设置为同一个类?
import UIKit
class MenuView: UIView, UICollectionViewDataSource {
let collcetionView: UICollectionView = {
let view = UICollectionView()
// Setup...
return view
}()
override init(frame: CGRect) {
super.init(frame: frame)
setupCollectionView()
collcetionView.dataSource = self
}
required init?(coder aDecoder: NSCoder) {
fatalError("init(coder:) has not been implemented")
}
fileprivate func setupCollectionView() {
// Autolayout code...
}
// Datasource methods to populate collection view cells
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
// Populate cell code...
}
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
// Populate cell code...
}
}
class MainView: UIView {
// Contains paging scroll view and menu bar
var menu: MenuView!
let scrollView: UIScrollView = {
let view = UIScrollView()
// Setup...
return view
}()
override init(frame: CGRect) {
super.init(frame: frame)
setupMenu()
setupScrollView()
}
required init?(coder aDecoder: NSCoder) {
fatalError("init(coder:) has not been implemented")
}
fileprivate func setupScrollView() {
// Autolayout code...
}
fileprivate func setupMenu() {
menu = MenuView()
// Autolayout code...
}
}
class MainController: UIViewController, UIScrollViewDelegate, UICollectionViewDelegate {
var mainView: MainView!
override func loadView() {
super.loadView()
mainView = MainView()
view = mainView
}
override func viewDidLoad() {
super.viewDidLoad()
mainView.scrollView.delegate = self
mainView.menu.collcetionView.delegate = self // <<--- THIS IS WHAT BREAKS EVERYTHING
}
func scrollViewDidScroll(_ scrollView: UIScrollView) {
// Moving menu bar with page scroll
mainView.menu.collectionView.contentOffset = CGPoint(x: scrollView.contentOffset.x/SCROLL_FACTOR - (firstIndexPosition/SCROLL_FACTOR - difference/2), y: 0)
// Fade in and out highlighted state of menu bar cell
let exactPage = (scrollView.contentOffset.x / SCREEN_WIDTH)
let currentPage = (scrollView.contentOffset.x / SCREEN_WIDTH).rounded()
let unitExact = currentPage - exactPage
//print(String(format: "exact: %.2f, ", exactPage) + "current: \(currentPage), " + String(format: "unit: %.2f, ", unitExact))
if exactPage > currentPage {
// exact > current
// fade out/in left icon
// select current
let unit = 0 - unitExact // from 0 - 0.5
let cell = mainView.menu.collectionView.cellForItem(at: IndexPath(item: Int(currentPage), section: 0)) as! MenuBarCell
let mapped = unit.map(from: 0.0...0.5, to: 0...149.0)
print(cell)
setCellColor(cell: cell, value: mapped)
} else if exactPage < currentPage {
// exact < current
// fade out/in right icon
// select current
let unit = unitExact // from 0 - 0.5
let cell = mainView.menu.collectionView.cellForItem(at: IndexPath(item: Int(currentPage), section: 0)) as! MenuBarCell
let mapped = unit.map(from: 0.0...0.5, to: 0...149.0)
setCellColor(cell: cell, value: mapped)
} else if exactPage == currentPage {
// exact = current
// darken that icon
// select current
}
}
}
UICollectionView
和UITableView
继承自UIScrollView
,
如果将两个对象的scrollViewDidScroll
设置为同一个类,则将为集合视图和scrollview调用delegate
委托方法。
你需要检查为什么要调用scrollViewDidScroll
并采取相应的行动。
最简单的方法是guard
语句,如果没有为您感兴趣的滚动视图调用委托方法,则返回该语句。
如果您需要执行不同的代码,具体取决于所涉及的滚动视图,您可以使用一系列if
语句或switch
语句。
func scrollViewDidScroll(_ scrollView: UIScrollView) {
guard scrollView == self.scrollView else {
return
}
// Moving menu bar with page scroll
mainView.menu.collectionView.contentOffset = CGPoint(x: scrollView.contentOffset.x/SCROLL_FACTOR - (firstIndexPosition/SCROLL_FACTOR - difference/2), y: 0)
// Fade in and out highlighted state of menu bar cell
let exactPage = (scrollView.contentOffset.x / SCREEN_WIDTH)
let currentPage = (scrollView.contentOffset.x / SCREEN_WIDTH).rounded()
let unitExact = currentPage - exactPage
//print(String(format: "exact: %.2f, ", exactPage) + "current: \(currentPage), " + String(format: "unit: %.2f, ", unitExact))
if exactPage > currentPage {
// exact > current
// fade out/in left icon
// select current
let unit = 0 - unitExact // from 0 - 0.5
let cell = mainView.menu.collectionView.cellForItem(at: IndexPath(item: Int(currentPage), section: 0)) as! MenuBarCell
let mapped = unit.map(from: 0.0...0.5, to: 0...149.0)
print(cell)
setCellColor(cell: cell, value: mapped)
} else if exactPage < currentPage {
// exact < current
// fade out/in right icon
// select current
let unit = unitExact // from 0 - 0.5
let cell = mainView.menu.collectionView.cellForItem(at: IndexPath(item: Int(currentPage), section: 0)) as! MenuBarCell
let mapped = unit.map(from: 0.0...0.5, to: 0...149.0)
setCellColor(cell: cell, value: mapped)
} else if exactPage == currentPage {
// exact = current
// darken that icon
// select current
}
}