我正在尝试在表格视图上实现平移手势，以在平移它们时选择多个单元格
我遇到的麻烦是，当用户平移表格中的最后一个可见单元格时，使tableview滚动到下一个单元格；或者当用户平移表格中的第一个可见单元格时，滚动到上一个单元格
当前，当我的平移到达表格中的最后一个可见行或第一个可见行时，它将为下一行进行动画处理，但仅对前2或3行进行动画处理，然后停止滚动
经过一番挖掘后，似乎是由于没有调用panGesture所致，因为用户的手指在桌子边缘文具了。
一旦平底锅到达桌子的顶部或底部边缘，我将如何保持桌子滚动？
这是我当前的代码：
import UIKit
class MyView: UIViewController, UITableViewDelegate, UITableViewDataSource, UIGestureRecognizerDelegate {
var lastSelectedCell = IndexPath()
var gesturePan: UIPanGestureRecognizer!
var totalRows = 100
@IBOutlet weak var tableView: UITableView!
override func viewDidLoad() {
super.viewDidLoad()
//setup table gestures
addGesturesToTable()
}
}
extension MyView{
//MARK: - Tableview code
func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return totalRows
}
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier: "cell", for: indexPath)
let lab = cell.viewWithTag(1) as! UILabel
lab.text = "\(indexPath.row)"
return cell
}
}
extension MyView{
//MARK: - Gesture code
func addGesturesToTable() {
tableView.canCancelContentTouches = false
tableView.allowsMultipleSelection = true
//add long press gesture to initiate pan
let gestureLongPress = UILongPressGestureRecognizer(target: self, action: #selector(enablePan))
gestureLongPress.minimumPressDuration = 0.25
gestureLongPress.delaysTouchesBegan = true
gestureLongPress.delegate = self
tableView.addGestureRecognizer(gestureLongPress)
//add pan gesture to select cells on drag
gesturePan = UIPanGestureRecognizer(target: self, action: #selector(userPanned(_:)))
gesturePan.isEnabled = false
gesturePan.delegate = self
tableView.addGestureRecognizer(gesturePan)
}
//LongPress gesture(to enable pan)
@objc func enablePan() {
gesturePan.isEnabled = true
}
//Pan gesture
@objc func userPanned(_ panGesture: UIPanGestureRecognizer) {
//if starting to pan
if panGesture.state == .began {
tableView?.isUserInteractionEnabled = false
tableView?.isScrollEnabled = false
//if pan position is changed
}else if panGesture.state == .changed {
//get indexPath at pan location
let location: CGPoint = panGesture.location(in: tableView)
if let indexPath: IndexPath = tableView?.indexPathForRow(at: location) {
//if the index path.row is the first or last row of the data set
if(indexPath.row >= totalRows - 1 || indexPath.row <= 0){
print("data start/end reached")
//otherwise
}else{
//get pan direction
var direction: String!
let velocity = panGesture.velocity(in: tableView)
if(velocity.y > 0){
direction = "Down"
}else{
direction = "Up"
}
//if it's a new cell
if indexPath != lastSelectedCell {
//select/deselect it
self.selectPannedCell(indexPath, selected: true, location: location, panDirection: direction)
//update last selected cell
lastSelectedCell = indexPath
}
}
}
//if pan gesture is ending
}else if panGesture.state == .ended {
//re-enable tableview interaction
tableView.isScrollEnabled = true
tableView.isUserInteractionEnabled = true
//disable pan gesture
panGesture.isEnabled = false
}
}
//select/deselect the panned over cell
func selectPannedCell(_ indexPath: IndexPath, selected: Bool, location: CGPoint, panDirection: String) {
if let cell = tableView.cellForRow(at: indexPath) {
//if cell is already selected
if cell.isSelected {
//deselect row
tableView.deselectRow(at: indexPath, animated: true)
//if panning down
if(panDirection == "Down"){
//if it's the last cell
if(indexPath >= tableView.indexPathsForVisibleRows![(tableView.indexPathsForVisibleRows?.count)!-1]){
//scroll to the next cell after the last visible
let scrollToIndex = IndexPath(row: indexPath.row + 1, section:0)
tableView.scrollToRow(at: scrollToIndex, at:
UITableViewScrollPosition.bottom, animated: true)
}
//if panning up
}else{
//if it's the first cell
if(indexPath <= tableView.indexPathsForVisibleRows![0]){
//scroll to the previous cell before first visible
let firstIndex = IndexPath(row: indexPath.row - 1, section:0)
tableView.scrollToRow(at: firstIndex, at:
UITableViewScrollPosition.top, animated: true)
}
}
} else {
//select row
tableView.selectRow(at: indexPath, animated: true, scrollPosition: UITableViewScrollPosition.none)
//if panning down
if(panDirection == "Down"){
//if it's the last cell
if(indexPath >= tableView.indexPathsForVisibleRows![(tableView.indexPathsForVisibleRows?.count)!-1]){
//scroll to the next cell after the last visible
let lastIndex = IndexPath(row: indexPath.row + 1, section:0)
tableView.scrollToRow(at: lastIndex, at:
UITableViewScrollPosition.bottom, animated: true)
}
}else{
//if it's the first cell
if(indexPath <= tableView.indexPathsForVisibleRows![0]){
//scroll to the previous cell before first visible
let firstIndex = IndexPath(row: indexPath.row - 1, section:0)
tableView.scrollToRow(at: firstIndex, at:
UITableViewScrollPosition.top, animated: true)
}
}
}
}
}
}
预先感谢
答案 0 :(得分：0)
这里有一个简单的示例，说明如何在您的情况下实现它，我认为您可以轻松地将其适合您的需求。
var continueScrollToBottom: Bool = false
var continueScrollToTop: Bool = false
@objc func updatePanGesture(_ sender: UIPanGestureRecognizer) {
switch sender.state {
case .changed:
continueScrollToBottom = false
continueScrollToTop = false
// If you reach to the top make scroll constant
// You can define there another condition which more suitable for you
if sender.location(in: self.view).y < 200 {
continueScrollToTop = true
continueScrollToBottom = false
self.startScrollToTop()
return
}
// If you reach to the bottom make scroll constant
// You can define there another condition which more suitable for you
if sender.location(in: self.view).y > 350 {
continueScrollToBottom = true
continueScrollToTop = false
self.startScrollToBottom()
return
}
case .ended:
continueScrollToBottom = false
continueScrollToTop = false
case .cancelled:
continueScrollToBottom = false
continueScrollToTop = false
default:
break
}
}
func startScrollToBottom() {
if continueScrollToBottom {
if let last = tableView.indexPathsForVisibleRows?.last, last.row+1 < countOfRows {
let showNext = IndexPath(row: last.row+1, section: last.section)
tableView.scrollToRow(at: showNext, at: .bottom, animated: true)
DispatchQueue.main.asyncAfter(deadline: .now()+0.3) {
self.startScrollToBottom()
}
}
}
}
func startScrollToTop() {
if continueScrollToTop {
if let first = tableView.indexPathsForVisibleRows?.first, first.row-1 > 0 {
let showNext = IndexPath(row: first.row-1, section: first.section)
tableView.scrollToRow(at: showNext, at: .top, animated: true)
DispatchQueue.main.asyncAfter(deadline: .now()+0.3) {
self.startScrollToTop()
}
}
}
}