通过手势交换单元格的位置

Question

我有UICollectionView，其中有一个原型单元和UIImageView。我在UICollectionView 中显示随机图像。

现在我想通过将UIImageView 滑动到单元格附近来交换它的位置。我尝试过滑动手势和长按手势。下面给出了我已经完成的代码：

- (IBAction)LongPress:(UILongPressGestureRecognizer *)sender
{
    if (sender.state != UIGestureRecognizerStateEnded) 
    {
        return;
    }
    CGPoint p = [sender locationInView:self.collectionView];

    NSIndexPath *indexPath = [self.coll_out indexPathForItemAtPoint:p];
    if (indexPath == nil)
    {
        NSLog(@"couldn't find index path");            
    }
    else 
    {
        // get the cell at indexPath (the one you long pressed)
        UICollectionViewCell* cell =[self.coll_out cellForItemAtIndexPath:indexPath];
        // do stuff with the cell
    }
}

还尝试了委托方法：

- (void)moveItemAtIndexPath:(NSIndexPath *)indexPath toIndexPath:(NSIndexPath *)newIndexPath
{
    NSMutableArray *item1=[arr_final objectAtIndex:indexPath.section];
    NSMutableArray *item2=[arr_final objectAtIndex:newIndexPath.section];
    NSLog(@"%@ %@",item1,item2);
    NSString *index = [item1 objectAtIndex:indexPath.item];
    [item1 removeObjectAtIndex:indexPath.item];
    [item2 insertObject:index atIndex:newIndexPath.item];
}

功能就像拖放一样。我见过的例子

• LXReorderableCollectionViewFlowLayout
• HTKDragAndDropCollectionViewLayout

请给我正确的方法和代码来刷到附近的单元格。 谢谢...

Answer 1

实际上我一直在使用LXReorderableCollectionViewFlowLayout，它非常适合您，并且在他们的存储库中也有一个示例。起初我不建议您使用滑动手势，因为它与 UICollectionView 的内部手势处理高度冲突，但如果您确定需要它，您必须实现添加手势的委托方法并解决同时手势，因为它正在执行 LXReordableCollectionViewFlowLayout:

- (BOOL)gestureRecognizerShouldBegin:(UIGestureRecognizer *)gestureRecognizer {
    if ([self.panGestureRecognizer isEqual:gestureRecognizer]) {
        return (self.selectedItemIndexPath != nil);
    }
    return YES;
}

- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldRecognizeSimultaneouslyWithGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer {
    if ([self.longPressGestureRecognizer isEqual:gestureRecognizer]) {
        return [self.panGestureRecognizer isEqual:otherGestureRecognizer];
    }

    if ([self.panGestureRecognizer isEqual:gestureRecognizer]) {
        return [self.longPressGestureRecognizer isEqual:otherGestureRecognizer];
    }

    return NO;
}

无论如何，我不建议您重新实现 LXReordableCollectionViewFlowLayout 中所做的事情，并将其用于您的需要。如果您使用 Storyboard，则需要将 UICollectionView 放入 UIViewController 并将默认 UICollectionViewFlowLayout 类更改为 LXReorderableCollectionViewFlowLayout 就像 此外，您的 UICollectionView 委托应符合下一个协议：LXReorderableCollectionViewDataSource（扩展 UICollectionViewDataSource）和 LXReorderableCollectionViewDelegateFlowLayout（扩展 UICollectionViewDelegateFlowLayout）允许您使用您的类。根据您的需要，只需提供下一个方法就足够了：

- (void)collectionView:(UICollectionView *)collectionView itemAtIndexPath:(NSIndexPath *)fromIndexPath willMoveToIndexPath:(NSIndexPath *)toIndexPath {
    id from = [items objectAtIndex:fromIndexPath.item];
    id to = [items objectAtIndex:toIndexPath.item];

    [items replaceObjectAtIndex:fromIndexPath.item withObject:to];
    [items replaceObjectAtIndex:toIndexPath.item withObject:from];;
}

- (BOOL)collectionView:(UICollectionView *)collectionView canMoveItemAtIndexPath:(NSIndexPath *)indexPath
{
    return YES;
}

- (BOOL)collectionView:(UICollectionView *)collectionView itemAtIndexPath:(NSIndexPath *)fromIndexPath canMoveToIndexPath:(NSIndexPath *)toIndexPath
{
    return YES;
}

要获得您需要的行为，您必须进入 LXReorderableCollectionViewFlowLayout 类并更改 invalidateLayoutIfNecessary 方法，以便它执行另一种更新，而不是以前：

- (void)invalidateLayoutIfNecessary {
    NSIndexPath *newIndexPath = [self.collectionView indexPathForItemAtPoint:self.currentView.center];
    NSIndexPath *previousIndexPath = self.selectedItemIndexPath;

    if ((newIndexPath == nil) || [newIndexPath isEqual:previousIndexPath]) {
        return;
    }

    if ([self.dataSource respondsToSelector:@selector(collectionView:itemAtIndexPath:canMoveToIndexPath:)] &&
        ![self.dataSource collectionView:self.collectionView itemAtIndexPath:previousIndexPath canMoveToIndexPath:newIndexPath]) {
        return;
    }

    self.selectedItemIndexPath = newIndexPath;

    if ([self.dataSource respondsToSelector:@selector(collectionView:itemAtIndexPath:willMoveToIndexPath:)]) {
        [self.dataSource collectionView:self.collectionView itemAtIndexPath:previousIndexPath willMoveToIndexPath:newIndexPath];
    }

    __weak typeof(self) weakSelf = self;
    [self.collectionView performBatchUpdates:^{
        __strong typeof(self) strongSelf = weakSelf;
        if (strongSelf) {
            // NOTE: cells swipe
            [strongSelf.collectionView moveItemAtIndexPath:previousIndexPath toIndexPath:newIndexPath];
            [strongSelf.collectionView moveItemAtIndexPath:newIndexPath toIndexPath:previousIndexPath];

            // NOTE: it was here previously
            // [strongSelf.collectionView deleteItemsAtIndexPaths:@[ previousIndexPath ]];
            // [strongSelf.collectionView insertItemsAtIndexPaths:@[ newIndexPath ]];
        }
    } completion:^(BOOL finished) {
        __strong typeof(self) strongSelf = weakSelf;
        if ([strongSelf.dataSource respondsToSelector:@selector(collectionView:itemAtIndexPath:didMoveToIndexPath:)]) {
            [strongSelf.dataSource collectionView:strongSelf.collectionView itemAtIndexPath:previousIndexPath didMoveToIndexPath:newIndexPath];
        }
    }];
}

它适用于靠近您初始项目的单元格，但是一旦您的卡移动，它可能会误导用户下一步将其移动到哪里，无论如何只需尝试一下，看看它是如何进行的。请记住，您可以通过 collectionView:itemAtIndexPath:canMoveToIndexPath: 方法控制项目的可用移动。

希望对您有所帮助。