当我开始水平滚动时，为什么我的收藏视图中的单元格被取消选择？

Question

我想从集合视图中制作一个简单的日历。 [在此处输入图片描述][1][1]：https://i.stack.imgur.com/1yXhL.jpg 但是当我选择一个单元格并开始滚动时，单元格会自动取消选择。这是我的集合视图代码。

    `let todayColor = UIColor(red: 242/255, green: 56/255, blue: 15/255, alpha: 1)
    let otherDayColor = UIColor(red: 90/255, green: 90/255, blue: 90/255, alpha: 1)
var now = Date()
    var day = DateFormatter()
    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
                        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "CellID", for: indexPath) as! CalenderCell
                        cell.layer.cornerRadius = 5
                        cell.backgroundColor = otherDayColor
                        if indexPath.row == 0{
                            cell.backgroundColor = todayColor
                            cell.dayLabel.text = (day.shortWeekdaySymbols[Calendar.current.component(.weekday, from: Date()) - 1])
                            cell.dateLabel.text = now.string(format: "dd")
                        }
                        else if indexPath.row == 1{
                            cell.backgroundColor = otherDayColor
                            cell.dayLabel.text = (day.shortWeekdaySymbols[Calendar.current.component(.weekday, from: myCalender(numDay: 1)) - 1])
                            cell.dateLabel.text = myCalender(numDay: 1).string(format: "dd")
                        }
                        else if indexPath.row == 2{
                            cell.backgroundColor = otherDayColor
                            cell.dayLabel.text = (day.shortWeekdaySymbols[Calendar.current.component(.weekday, from: myCalender(numDay: 2)) - 1])
                            cell.dateLabel.text = myCalender(numDay: 2).string(format: "dd")
                        }
                        else if indexPath.row == 3{
                            cell.backgroundColor = otherDayColor
                            cell.dayLabel.text = (day.shortWeekdaySymbols[Calendar.current.component(.weekday, from: myCalender(numDay: 3)) - 1])
                            cell.dateLabel.text = myCalender(numDay: 3).string(format: "dd")
                        }
                        else if indexPath.row == 4{
                            cell.backgroundColor = otherDayColor
                            cell.dayLabel.text = (day.shortWeekdaySymbols[Calendar.current.component(.weekday, from: myCalender(numDay: 4)) - 1])
                            cell.dateLabel.text = myCalender(numDay: 4).string(format: "dd")
                        }
                        else if indexPath.row == 5{
                            cell.backgroundColor = otherDayColor
                            cell.dayLabel.text = (day.shortWeekdaySymbols[Calendar.current.component(.weekday, from: myCalender(numDay: 5)) - 1])
                            cell.dateLabel.text = myCalender(numDay: 5).string(format: "dd")
            }
            else if indexPath.row == 6{
            cell.backgroundColor = otherDayColor
            cell.dayLabel.text = (day.shortWeekdaySymbols[Calendar.current.component(.weekday, from: myCalender(numDay: 6)) - 1])
            cell.dateLabel.text = myCalender(numDay: 6).string(format: "dd")
            }
            return cell
            }

        func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
                if let cell = collectionView.cellForItem(at: indexPath){
                    if indexPath.row == 0{
                        cell.backgroundColor = todayColor
                    }
                    else{
                        cell.backgroundColor = UIColor.systemGreen
                    }
                }
            }

            func collectionView(_ collectionView: UICollectionView, didDeselectItemAt indexPath: IndexPath) {
                if let cell = collectionView.cellForItem(at: indexPath){
                    cell.backgroundColor = otherDayColor
                }
            }`

Answer 1

这是因为您在 didSelect 方法中配置了选择颜色，但在 cellForItemAt 中没有配置。您需要使用所选项目索引创建变量（并将其设置为didSelect）并在cellForItemAt 中更新颜色管理。

在视图控制器中实现选定项索引：

var selectedItem: Int?

在您的集合视图委托方法中：

func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
    let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "CellID", for: indexPath) as! CalenderCell
    cell.layer.cornerRadius = 5
    cell.backgroundColor = otherDayColor
    if indexPath.row == 0{
        cell.dayLabel.text = (day.shortWeekdaySymbols[Calendar.current.component(.weekday, from: Date()) - 1])
        cell.dateLabel.text = now.string(format: "dd")
    }
    else if indexPath.row == 1{
        cell.dayLabel.text = (day.shortWeekdaySymbols[Calendar.current.component(.weekday, from: myCalender(numDay: 1)) - 1])
        cell.dateLabel.text = myCalender(numDay: 1).string(format: "dd")
    }
    else if indexPath.row == 2{
        cell.dayLabel.text = (day.shortWeekdaySymbols[Calendar.current.component(.weekday, from: myCalender(numDay: 2)) - 1])
        cell.dateLabel.text = myCalender(numDay: 2).string(format: "dd")
    }
    else if indexPath.row == 3{
        cell.dayLabel.text = (day.shortWeekdaySymbols[Calendar.current.component(.weekday, from: myCalender(numDay: 3)) - 1])
        cell.dateLabel.text = myCalender(numDay: 3).string(format: "dd")
    }
    else if indexPath.row == 4{
        cell.dayLabel.text = (day.shortWeekdaySymbols[Calendar.current.component(.weekday, from: myCalender(numDay: 4)) - 1])
        cell.dateLabel.text = myCalender(numDay: 4).string(format: "dd")
    }
    else if indexPath.row == 5{
        cell.dayLabel.text = (day.shortWeekdaySymbols[Calendar.current.component(.weekday, from: myCalender(numDay: 5)) - 1])
        cell.dateLabel.text = myCalender(numDay: 5).string(format: "dd")
    }
    else if indexPath.row == 6{
        cell.dayLabel.text = (day.shortWeekdaySymbols[Calendar.current.component(.weekday, from: myCalender(numDay: 6)) - 1])
        cell.dateLabel.text = myCalender(numDay: 6).string(format: "dd")
    }

    if indexPath.row == 0 {
        cell.backgroundColor = todayColor
    } else {
        if let selectedItem = selectedItem,
           selectedItem == indexPath.row {
            // this cell is selected
            cell.backgroundColor = UIColor.systemGreen
        } else {
            cell.backgroundColor = otherDayColor
        }
    }
    return cell
}

func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
    if let cell = collectionView.cellForItem(at: indexPath) {
        selectedItem = indexPath.row // set selectedItem
        if indexPath.row == 0 {
            cell.backgroundColor = todayColor
        } else{
            cell.backgroundColor = UIColor.systemGreen
        }
    }
}

在didDeselectItemAt中需要设置selectedItem为nil。

使用switch-case 代替if 也很好