UICollectionView 和 Selected Cell 在滚动时失去选择

Question

我有一个 UICollectionView，一切正常，但是，有一件事情我无法处理（我不知道如何处理），我有一个单元格集合，可以查看用户需要滚动的所有单元格像往常一样向下或向上。

当用户选择单元格时，内容变为“红色”，红色为“选中”单元格，黑色为“未选中”单元格或正常状态。

当所选单元格落在导航栏或标签栏后面时，该单元将失去“红色”并再次变为黑色，如“未选择”。

如何在 uicollectionview 滚动时单元格落后时保持“红色”？

override func collectionView(collectionView: UICollectionView, didSelectItemAtIndexPath indexPath: NSIndexPath) {
    let cell = collectionView.cellForItemAtIndexPath(indexPath)

    let icon = cell!.viewWithTag(10) as? UIImageView
    icon!.image = icon!.image! .imageWithRenderingMode(UIImageRenderingMode.AlwaysTemplate)
    icon!.tintColor = UIColor.redColor()

    let label = cell!.viewWithTag(100) as? UILabel
    label?.textColor = UIColor.redColor()
    //print("Seleccionado")

}

override func collectionView(collectionView: UICollectionView, didDeselectItemAtIndexPath indexPath: NSIndexPath) {
    let cell = collectionView.cellForItemAtIndexPath(indexPath)

    cell!.contentView.backgroundColor = nil
    cell!.contentView.layer.borderColor = nil

    let icon = cell!.viewWithTag(10) as? UIImageView
    icon!.image = icon!.image! .imageWithRenderingMode(UIImageRenderingMode.AlwaysTemplate)
    icon!.tintColor = UIColor.blackColor()

    let label = cell!.viewWithTag(100) as? UILabel
    label?.textColor = UIColor.lightGrayColor()
    //print("Unselect")
}

override func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell {
    let cell = collectionView.dequeueReusableCellWithReuseIdentifier(reuseIdentifier, forIndexPath: indexPath) as! ObjectosCollectionViewCell

    cell.objectoNameLabel.text = objectosData[indexPath.row]
    cell.objectoNameLabel.textColor = UIColor.lightGrayColor()
    cell.objectoImageView.image = UIImage(named:objectosImage[indexPath.row])

    return cell
}

谢谢

Answer 1

你需要对你的逻辑做一些修改；

//CollectionViewCell Custom Class
import UIKit

class CollectionViewCell: UICollectionViewCell {

    override var selected: Bool {
        get {
            return super.selected;
        }

        set {
            if (super.selected != newValue) {
                super.selected = newValue

                let icon = self.viewWithTag(10) as? UIImageView
                icon?.image = icon?.image!.imageWithRenderingMode(UIImageRenderingMode.AlwaysTemplate)

                let label = self.viewWithTag(100) as? UILabel

                if (newValue == true) {
                    icon?.tintColor = UIColor.redColor()
                    label?.textColor = UIColor.redColor()
                } else {
                    icon?.tintColor = UIColor.blackColor()
                    label?.textColor = UIColor.lightGrayColor()
                }
            }
        }
    } //P.E.

}

然后;

//Define a class variable in your viewController
var cellStatus:NSMutableDictionary = NSMutableDictionary();

//Collection view delegate methods
func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell {

    var cell:CollectionViewCell? = collectionView.dequeueReusableCellWithReuseIdentifier(reuseIdentifier, forIndexPath: indexPath) as? CollectionViewCell;

    cell!.selected = (cellStatus[indexPath.row] as? Bool) ?? false;

    return cell!;
}

func collectionView(collectionView: UICollectionView, didSelectItemAtIndexPath indexPath: NSIndexPath) {
    //Updating cell status
    let cell = collectionView.cellForItemAtIndexPath(indexPath)
    cell?.selected = true;

    //Updating dic
    self.cellStatus[indexPath.row] = true;
}

func collectionView(collectionView: UICollectionView, didDeselectItemAtIndexPath indexPath: NSIndexPath) {
    //Updating cell status
    let cell = collectionView.cellForItemAtIndexPath(indexPath)
    cell?.selected = false;

    //Updating dic
    self.cellStatus[indexPath.row] = false;
}

注意：改变图片图标颜色的方法不好。它占用了太多的处理能力，可能会挂起滚动。每个状态应该使用两个单独的图像。

Answer 2

这发生在我的 UITableView 上，似乎每次您上下滚动显示更多元素时，单元格都会再次呈现。所以我遇到的解决方案是创建一个名为 selecteditems 的数组，每次用户选择该单元格时，都会将该单元格的索引保存在数组中。 像这样

  override func collectionView(collectionView: UICollectionView, didSelectItemAtIndexPath indexPath: NSIndexPath) {
let cell = collectionView.cellForItemAtIndexPath(indexPath)

let icon = cell!.viewWithTag(10) as? UIImageView
icon!.image = icon!.image! .imageWithRenderingMode(UIImageRenderingMode.AlwaysTemplate)
icon!.tintColor = UIColor.redColor()

let label = cell!.viewWithTag(100) as? UILabel
label?.textColor = UIColor.redColor()

//Save in array
selecteditems.append(indexPath.row)

}

override func collectionView(collectionView: UICollectionView, didDeselectItemAtIndexPath indexPath: NSIndexPath) {
    let cell = collectionView.cellForItemAtIndexPath(indexPath)

    cell!.contentView.backgroundColor = nil
    cell!.contentView.layer.borderColor = nil

    let icon = cell!.viewWithTag(10) as? UIImageView
    icon!.image = icon!.image! .imageWithRenderingMode(UIImageRenderingMode.AlwaysTemplate)
    icon!.tintColor = UIColor.blackColor()

    let label = cell!.viewWithTag(100) as? UILabel
    label?.textColor = UIColor.lightGrayColor()


    if selecteditems.contains(indexPath.row){
      // place your code to be red
    }

}