ios - 如何在旋转期间删除 UICollectionView 的淡入淡出动画？

Question

我只是想在旋转期间调整 CollectionView 的动画，这样就不会出现像这样的淡入淡出效果

只需简单地移动 View 即可。 因此，经过一番小小的搜索后，我发现我只需通过以下方式即可实现该效果 重写 UICollectionViewFlowLayout 的两个方法

 override func initialLayoutAttributesForAppearingItem(at itemIndexPath: IndexPath) -> UICollectionViewLayoutAttributes? {

return nil

}
 override func finalLayoutAttributesForDisappearingItem(at itemIndexPath: IndexPath) -> UICollectionViewLayoutAttributes? {
      return layoutAttributesForItem(at: itemIndexPath) 

}

但是另一个问题出现了:当我在两条消息之间接收消息时，例如接收延迟消息 蓝色消息不仅会向下移动，而且蓝色消息的旧实例也会在原地停留很短一段时间，然后就会向下移动。但如果我返回到最初的偏好

  override func initialLayoutAttributesForAppearingItem(at itemIndexPath: IndexPath) -> UICollectionViewLayoutAttributes? {

return nil

}
 override func finalLayoutAttributesForDisappearingItem(at itemIndexPath: IndexPath) -> UICollectionViewLayoutAttributes? {
      return nil 

}

消息以整齐的方式适当移动，但在旋转过程中再次出现褪色效果。

这件事让我很困惑，也许有人有任何线索，我怎样才能保持旋转动画而不褪色效果并使消息动画效果像普通消息运动一样。

Answer 1

我想我找到了解决方案。 1)我需要找出CollectionView中插入的元素的IndexPaths。 2)计算插入 IndexPath 后放置的下一个元素(当我在两条消息之间接收消息时，例如接收延迟消息) 3)将新的initialLayoutAttributesForAppearingItem和finalLayoutAttributesForDisappearingItem应用到上面派生的IndexPaths数组，对于其余元素，我们只应用该首选项

 override func initialLayoutAttributesForAppearingItem(at itemIndexPath: IndexPath) -> UICollectionViewLayoutAttributes? {

return nil

}
    override func finalLayoutAttributesForDisappearingItem(at itemIndexPath: IndexPath) -> UICollectionViewLayoutAttributes? {
  return layoutAttributesForItem(at: itemIndexPath) 

 }

这是代码

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

    super.prepare(forCollectionViewUpdates: updateItems)
               insertingIndexPaths.removeAll()
    print("begining : \(insertingIndexPaths)")


    // create an array

    let fullAmountOfCells = collectionView?.numberOfItems(inSection: 0)
    print("number of items: \(fullAmountOfCells)")

    for update in updateItems {
        if let indexPath = update.indexPathAfterUpdate,
            update.updateAction == .insert {
            insertingIndexPaths.append(indexPath)
            print("Example if indexPath if for loop:\(indexPath)")
        }

   }
    let lastPathOfInsertingElement = insertingIndexPaths.last
    let differenceBetweenFullAmountAndLastInsertElement = fullAmountOfCells! - (lastPathOfInsertingElement?.item)! - 1

    if differenceBetweenFullAmountAndLastInsertElement > 0 {
        for numeric in 1...differenceBetweenFullAmountAndLastInsertElement {
            insertingIndexPaths.append(IndexPath(item: numeric + (lastPathOfInsertingElement?.item)!, section: 0))
        }
        print("True array to be modified with attributes:\(insertingIndexPaths)")

}
 }

override func finalizeCollectionViewUpdates() {
    super.finalizeCollectionViewUpdates()
  //  ChatLogController.orientation = UIDevice.current.orientation
//    print(  ChatLogController.orientation = UIDevice.current.orientation)
    insertingIndexPaths.removeAll()
    movingIndexPath.removeAll()
}



   override func initialLayoutAttributesForAppearingItem(at itemIndexPath: IndexPath) -> UICollectionViewLayoutAttributes? {
    let attributes = super.initialLayoutAttributesForAppearingItem(at: itemIndexPath)

    if insertingIndexPaths.contains(itemIndexPath) {
        // attributes?.alpha = 0.0
        //attributes?.transform = CGAffineTransform(scaleX: 0.1, y: 0.1)

        print("Process in initialLayoutAttributesForAppearingItem: \(itemIndexPath)")
           return attributes

    } else {
         print("Process in initialLayout set to nil: \(itemIndexPath)")
        return nil
    }


}








  override func finalLayoutAttributesForDisappearingItem(at itemIndexPath: IndexPath) -> UICollectionViewLayoutAttributes? {
let attributes = super.initialLayoutAttributesForAppearingItem(at: itemIndexPath)

if insertingIndexPaths.contains(itemIndexPath) {
    // attributes?.alpha = 0.0
    //attributes?.transform = CGAffineTransform(scaleX: 0.1, y: 0.1)


    return nil

} else {
    print("processing final layout and it to leyoutAttributeForItem(at: \(itemIndexPath)")
    return layoutAttributesForItem(at:itemIndexPath)
}



  }