Question

我有一个水平集合视图，每个单元格都有自己的宽度。我使用默认的UICollectionViewFlowLayout。重新排列时，细胞继承了在此运动过程中覆盖的细胞宽度，这是我不想要的。任何想法，如何避免这种行为？

Answer 1

因此，如果您使用不同大小的单元格的UICollectionView，并且您希望在使用标准UICollectionViewFlowLayout移动时保持其大小，请使用：

extension UICollectionViewFlowLayout {

@available(iOS 9.0, *)
open override func invalidationContext(forInteractivelyMovingItems targetIndexPaths: [IndexPath], withTargetPosition targetPosition: CGPoint, previousIndexPaths: [IndexPath], previousPosition: CGPoint) -> UICollectionViewLayoutInvalidationContext {

    let context = super.invalidationContext(forInteractivelyMovingItems: targetIndexPaths, withTargetPosition: targetPosition, previousIndexPaths: previousIndexPaths, previousPosition: previousPosition)

    //Check that the movement has actually happeneds
    if previousIndexPaths.first!.item != targetIndexPaths.first!.item {
        collectionView?.dataSource?.collectionView?(collectionView!, moveItemAt: previousIndexPaths.first!, to: targetIndexPaths.last!)
    }

    return context
}

open override func invalidationContextForEndingInteractiveMovementOfItems(toFinalIndexPaths indexPaths: [IndexPath], previousIndexPaths: [IndexPath], movementCancelled: Bool) -> UICollectionViewLayoutInvalidationContext {
    return super.invalidationContextForEndingInteractiveMovementOfItems(toFinalIndexPaths: indexPaths, previousIndexPaths: previousIndexPaths, movementCancelled: movementCancelled)
}

@available(iOS 9.0, *) //If you'd like to apply some formatting as the dimming of the movable cell
open override func layoutAttributesForInteractivelyMovingItem(at indexPath: IndexPath, withTargetPosition position: CGPoint) -> UICollectionViewLayoutAttributes {
    let attributes = super.layoutAttributesForInteractivelyMovingItem(at: indexPath, withTargetPosition: position)
    attributes.alpha = 0.8
    return attributes
}

}

在你的控制器的moveItemAt方法中，不要忘记检查压力状态是否改变如下：

override func collectionView(_ collectionView: UICollectionView, moveItemAt sourceIndexPath: IndexPath,
                             to destinationIndexPath: IndexPath) {

    if #available(iOS 9.0, *) {

        if self.longPressureGestureRecognizer.state == .ended {
            return
        }

        //Update your data
        data.moveItem(at: sourceIndexPath.row, to: destinationIndexPath.row)

    }
}

Answer 2

我通过使用collectionView:targetIndexPathForMoveFromItemAtIndexPath:toProposedIndexPath:来解决这个问题，如果我的行/部分数据的副本不存在，我会创建它，然后更新副本，就好像建议的移动是实际移动一样。我的collectionView:layout:sizeForItemAtIndexPath:会使用该副本（如果存在）。我会在collectionView:moveItemAtIndexPath:toIndexPath:中将副本设置为nil，以便视图将返回使用“原始”行/节数据进行大小调整。因此，在移动之前，期间和之后，所有尺寸看起来都是正确的。

根据要求，这是我的代码：

- (NSIndexPath *)collectionView:(UICollectionView *)collectionView targetIndexPathForMoveFromItemAtIndexPath:(NSIndexPath *)originalIndexPath toProposedIndexPath:(NSIndexPath *)proposedIndexPath
{
    if (nil == _movingSections)
        _movingSections = [_sections copy];
    NSMutableArray *section = [_movingSections.sections objectAtIndex:originalIndexPath.section];
    id obj = [section objectAtIndex:originalIndexPath.row];

    [section removeObjectAtIndex:originalIndexPath.row];

    section = [_movingSections.sections objectAtIndex:proposedIndexPath.section];
    if (proposedIndexPath.row < [section count])
        [section insertObject:obj atIndex:proposedIndexPath.row];
    else
        [section addObject:obj];

    return proposedIndexPath;
}

当_movingSections为非零时，我还更新了collectionView:layout:sizeForItemAtIndexPath:以使用_movingSections而不是_sections。在collectionView:moveItemAtIndexPath:toIndexPath:中，我将_movingSections设置为nil。就是这样！

我应该补充一点，我最终放弃了这个方法，因为我的部分可以比设备宽度更宽，这可以正常工作，直到你移动东西，并且在那一点上UICollectionViewFlowLayout想要均匀地分隔单元格而不管你的宽度提供了。相反，我转而使用UIScrollView，现在我的代码更简单，而且我不再与UICollectionViewFlowLayout抗争。我考虑过滚动自己的UICollectionViewLayout，但这并没有使我的代码更简单。

移动时，将自定义单元格的大小保留在UICollectionView中

2 个答案: