[英]Get Visible Cell Index Path in CollectionView
我有一個垂直UICollectionView
我有在頂部和底部的兩個指標UICollectionView
。 我有15個牢房。 但是當前只有10個可見。 如果單元格0不可見,我想顯示頂部垂直指示器,表明頂部有一些單元格。 如果單元格零可見,則頂部不需要指示器
同樣,如果當前時間不顯示“底部”中的單元格,則希望具有“底部指示器”。
我為此創建了一個示例視圖控制器。 希望對您有幫助。 我添加了兩個按鈕作為指示器(頂部和底部)。 希望對您有幫助。
這就是ViewController的樣子
代碼:
//
// ViewController.swift
// Assignment
//
// Created by Anuradh Caldera on 4/16/19.
// Copyright © 2019 All rights reserved.
//
import UIKit
class ViewController: UIViewController {
private var customtableView: UITableView!
private var cellidentifier = "cellIdentifier"
private var topButton: UIButton!
private var bottomButton: UIButton!
override func viewDidLoad() {
super.viewDidLoad()
setuptableview()
setupButtons()
}
}
extension ViewController {
fileprivate func setuptableview() {
customtableView = UITableView(frame: .zero, style: .plain)
customtableView.translatesAutoresizingMaskIntoConstraints = false
customtableView.register(UITableViewCell.self, forCellReuseIdentifier: cellidentifier)
customtableView.dataSource = self
customtableView.delegate = self
view.addSubview(customtableView)
let customtableviewConstraints = [customtableView.leftAnchor.constraint(equalTo: view.leftAnchor),
customtableView.topAnchor.constraint(equalTo: view.topAnchor, constant: 50),
customtableView.rightAnchor.constraint(equalTo: view.rightAnchor),
customtableView.bottomAnchor.constraint(equalTo: view.bottomAnchor, constant: -50)]
NSLayoutConstraint.activate(customtableviewConstraints)
}
}
extension ViewController {
fileprivate func setupButtons() {
topButton = UIButton()
topButton.translatesAutoresizingMaskIntoConstraints = false
topButton.setTitle("Go Top", for: .normal)
topButton.backgroundColor = .purple
topButton.setTitleColor(.white, for: .normal)
topButton.isHidden = true
view.addSubview(topButton)
let topbuttonConstraints = [topButton.leftAnchor.constraint(equalTo: view.leftAnchor),
topButton.topAnchor.constraint(equalTo: view.topAnchor),
topButton.rightAnchor.constraint(equalTo: view.rightAnchor),
topButton.heightAnchor.constraint(equalToConstant: 50)]
NSLayoutConstraint.activate(topbuttonConstraints)
bottomButton = UIButton()
bottomButton.translatesAutoresizingMaskIntoConstraints = false
bottomButton.setTitle("Go Bottom", for: .normal)
bottomButton.backgroundColor = .purple
bottomButton.setTitleColor(.white, for: .normal)
bottomButton.isHidden = false
view.addSubview(bottomButton)
let bottomButtonConstraints = [bottomButton.leftAnchor.constraint(equalTo: view.leftAnchor),
bottomButton.bottomAnchor.constraint(equalTo: view.bottomAnchor),
bottomButton.rightAnchor.constraint(equalTo: view.rightAnchor),
bottomButton.heightAnchor.constraint(equalToConstant: 50)]
NSLayoutConstraint.activate(bottomButtonConstraints)
}
}
extension ViewController: UITableViewDataSource {
func numberOfSections(in tableView: UITableView) -> Int {
return 1
}
func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return 30 // use your desired number of cells here and change other according to the cell count.
}
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier: cellidentifier)
cell?.textLabel?.text = "cell \(indexPath.row)"
return cell!
}
}
extension ViewController: UITableViewDelegate, UIScrollViewDelegate {
func scrollViewWillBeginDragging(_ scrollView: UIScrollView) {
topButton.isHidden = true
bottomButton.isHidden = false
}
func scrollViewDidScroll(_ scrollView: UIScrollView) {
let visiblerect = CGRect(origin: customtableView.contentOffset, size: customtableView.bounds.size)
let visiblepoint = CGPoint(x: visiblerect.minX, y: visiblerect.minY)
if let visibleindexpath = customtableView.indexPathForRow(at: visiblepoint) {
if visibleindexpath.row == 0 {
topButton.isHidden = true
} else {
topButton.isHidden = false
}
}
for cell in customtableView.visibleCells {
if let indexpath = customtableView.indexPath(for: cell) {
print("visible cell from cell : \(indexpath.row)")
if indexpath.row == 29 {
bottomButton.isHidden = true
} else {
bottomButton.isHidden = false
}
}
}
}
}
我已經以編程方式創建了UI,以使其易於理解。 您可以使用此腳本或情節提要。 歡呼,祝你有美好的一天。
[![you need to take one button inside a UIView][1]][1]
@IBOutlet weak var topMoveView: ViewDesign!
@IBOutlet weak var topMoveButton: ButtonDesign!
override func viewWillAppear(_ animated: Bool) {
topMoveView.isHidden = true
topMoveButton.isHidden = true
}
extension testViewController : UICollectionViewDelegate, UICollectionViewDataSource, UICollectionViewDelegateFlowLayout {
func scrollViewDidScroll(_ scrollView: UIScrollView) {
if (testCollectionView.contentOffset.y <= 0) {
topMoveView.isHidden = true
topMoveButton.isHidden = true
}else{
topMoveView.isHidden = false
topMoveButton.isHidden = false
}
}
}
@IBAction func topMoveButtonPressed(_ sender: ButtonDesign) {
self.testCollectionView.setContentOffset(.zero, animated: true)
}
let arrayOfVisibleItems = collectionView.indexPathsForVisibleItems.sorted()
let lastIndexPath = arrayOfVisibleItems.last
let firstIndexPath = arrayOfVisibleItems.first
然后,您可以推斷出自己的邏輯以顯示想要顯示的內容
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