ios - 插入多個自定義補充視圖時的流佈局動畫故障

下面是CustomCollectionViewController文件的輸出indexPath項目用於cellForItemAt indexPath ， Row Supplementary用於viewForSupplementaryElementOfKind 。

正如您所看到的， cellForItemAt正確地返回了indexpath.item但是在viewForSupplementaryElementOfKind中沒有返回預期的答案。 如果我能盡快給你更新，我現在還沒有理由。

因此，對於重新求解，您可以通過在其中添加新數據來處理數組並重新加載collectionView而不是indexPath。

我不確定我是否對初始問題有正確的解決方案，但我遇到的問題與@agent_stack的答案相同。

如果您有自定義集合視圖佈局（UICollectionViewLayout的子類或UICollectionViewFlowLayout的子類）並添加自己的補充視圖，則必須覆蓋其他方法： indexPathsToInsertForSupplementaryView(ofKind elementKind: String)

每當向集合視圖添加單元格或節時，集合視圖都會調用此方法。 實現此方法使您的佈局對像有機會添加新的補充視圖以補充添加。

我做了我自己的CollectionViewFlowLayout，只有在組合添加這些方法之後，一切都是動畫應有的！

    override func prepare(forCollectionViewUpdates updateItems: [UICollectionViewUpdateItem]) {
    super.prepare(forCollectionViewUpdates: updateItems)

    // Prepare update by storing index path to insert
    // ────────────────────────────────────────────────────────────

    // IMPORTANT: Item vs. Section Update
    //
    // An instance of UICollectionViewUpdateItem can represent either an item or a section update,
    // and the only way to tell which is that update items which represent section updates contain
    // index paths with a valid section index and NSNotFound for the item index, while update items
    // that represent item updates contain index paths with valid item indexes.
    //
    // This appears to be completely undocumented by Apple, but it is absolutely consistent behavior.

    // https://www.raizlabs.com/blog/2013/10/animating_items_uicollectionview/

    var indexPaths = [IndexPath]()

    for updateItem in updateItems {

        switch updateItem.updateAction {

        case .insert:

            // If it is a section update then convert NSNotFound to zero.
            // In our case a section update always has only the first item.

            if var indexPath = updateItem.indexPathAfterUpdate {
                if indexPath.item == NSNotFound { indexPath.item = 0 }
                indexPaths.append(indexPath)
            }

        default:
            break
        }
    }

    indexPathsToInsert = indexPaths
}

override func indexPathsToInsertForSupplementaryView(ofKind elementKind: String) -> [IndexPath] {

    // Extra add supplementary index paths
    // ────────────────────────────────────────────────────────────

    // The collection view calls this method whenever you add cells or sections to the collection view.
    // Implementing this method gives your layout object an opportunity to add new supplementary views
    // to complement the additions.

    // http://.com/a/38289843/7441991

    switch elementKind {

    case UICollectionElementKindDateSeparator:
        return indexPathsToInsert

    case UICollectionElementKindAvatar:
        return indexPathsToInsert

    default:
        // If it is not a custom supplementary view, return attributes from flow layout
        return super.indexPathsToInsertForSupplementaryView(ofKind: elementKind)
    }
}

如果您有任何疑問，請隨時與我聯繫！ :)