ios - didSelectItemAtIndexPath 修改 UICollectionView 中的多个单元格

Question

我有包含 30 个项目的 Collection View ，并且想在媒体上执行一些操作。我是这样做的:

func collectionView(collectionView: UICollectionView, didSelectItemAtIndexPath indexPath: NSIndexPath) {

    let cell = collectionView.cellForItemAtIndexPath(indexPath) as! ItemCell

    var translucentView = ILTranslucentView(frame: CGRectMake(0, 0, cell.contentView.frame.size.width, cell.contentView.frame.size.height))
    translucentView.translucentAlpha = 0.9
    translucentView.translucentStyle = UIBarStyle.BlackTranslucent
    translucentView.translucentTintColor = UIColor.clearColor()
    translucentView.backgroundColor = UIColor.clearColor()
    translucentView.alpha = 0.0
    cell.contentView.addSubview(translucentView)
    UIView.animateWithDuration(0.4, animations: {
        translucentView.alpha = 1.0
    })
}

该功能按预期工作，但 View 不仅出现在点击的单元格上，而且出现在屏幕上不可见的相同位置的单元格上。因此，如果屏幕上有 3 个可见单元格，我点击数字 1，那么当我滚动时， View 已添加到单元格 4、7 等...

Answer 1

UICollectionView 重复使用单元格，就像 UITableView 一样。当单元格滚动到屏幕外时，它会被添加到队列中，并将被重新用于屏幕上滚动的下一个单元格(例如单元格 4、7 ...)。

只需删除 translucentView 即可解决此问题:

UIView.animateWithDuration(0.4, animations: { () -> Void in
    translucentView.alpha = 1.0
}) { (finish) -> Void in
    translucentView.removeFromSuperview()
}

您可以在 ItemCell 中创建 translucentView 并在 cellForItemAtIndexPath 方法中更新其状态:

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

    if find(collectionView.indexPathsForSelectedItems() as! [NSIndexPath], indexPath) != nil {
        cell.translucentView.alpha = 1.0
    } else {
        cell.translucentView.alpha = 0.0
    }

    return cell
}

override func collectionView(collectionView: UICollectionView, didSelectItemAtIndexPath indexPath: NSIndexPath) {

    let cell = collectionView.cellForItemAtIndexPath(indexPath) as! ItemCell

    UIView.animateWithDuration(0.4, animations: {
        cell.translucentView.alpha = 1.0
    })
}

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

    UIView.animateWithDuration(0.4, animations: {
        cell.translucentView.alpha = 0.0
    })
}