ios - 如何将 UICollectionViewCell 从一个 UICollectionView 拖到另一个 UICollectionView？

Question

我正在制作一个 iPad 应用程序。在此应用程序的一个页面上，左侧有一个 UICollectionView，右侧有另一个 UICollectionView。每个 UICollectionView 都是一列宽。

我想要的功能如下:左侧的每个 UICollectionViewCell 都应该能够被拖动到右侧的 UICollectionView。如果这不可能，那么至少应该能够将 UICollectionViewCell 从左侧的 UICollectionView 中拖出，然后我会处理让它出现在右侧的 UICollectionView 中。

这个功能可行吗？如果是这样，我将如何实现它？

Answer 1

您可能希望将长按手势识别器附加到两个 collectionView 的公共(public)父 View 。拖动操作由长按触发，整个事务在该识别器中处理。因为平移手势用于滚动 Collection View ，所以您在尝试使用平移识别器时会遇到问题。

关键是手势识别器需要附加到COMMON superview，所有的点和矩形都转换到superview的坐标系。

这不是确切的代码(它从 CV 移动到另一个 View )但过程是相似的(注意:我试图删除一些与您的应用程序无关的代码，所以我可能搞砸了过程中发生了一些事情——但这个概念是成立的):

- (void) processLongPress:(UILongPressGestureRecognizer *)sender
{
if (sender.state == UIGestureRecognizerStateChanged)
{
    if (!dragView)
        return;
    CGPoint location = [sender locationInView:self.view];
    CGPoint translation;
    translation.x = location.x - dragViewStartLocation.x;
    translation.y = location.y - dragViewStartLocation.y;
    CGAffineTransform theTransform = dragView.transform;
    theTransform.tx = translation.x;
    theTransform.ty = translation.y;
    dragView.transform = theTransform;
    [self.view bringSubviewToFront:dragView];
    return;
}   

if (sender.state == UIGestureRecognizerStateBegan)
{
    //  if point gives a valid collectionView indexPath we are doing a long press on a picture item to begin a drag
    //  & drop operation.
    CGPoint point = [sender locationInView:collectionView];
    dragViewIndexPath = [collectionView indexPathForItemAtPoint:point];
    if (dragViewIndexPath)  // i.e., selected item in collection view.
    {
        UICollectionViewCell *cell = [collectionView cellForItemAtIndexPath:dragViewIndexPath];
        dragView = [cell.contentView viewWithTag:cell.tag];
        [dragView removeFromSuperview];
        [self.view addSubview:dragView];
        dragView.center = [collectionView convertPoint:point toView:self.view];
        dragViewStartLocation = dragView.center;
        [self.view bringSubviewToFront:dragView];
    }
    return;
}

if (sender.state == UIGestureRecognizerStateEnded)
{
    if (dragView)
    {
        dragView.center = CGPointMake(dragView.center.x + dragView.transform.tx, dragView.center.y + dragView.transform.ty);
        CGAffineTransform theTransform = dragView.transform;
        theTransform.tx = 0.0f;
        theTransform.ty = 0.0f;
        UIView *dropTarget = [self mapDisplayModeToReceiverView];   // get drop target

        CGRect convertedTargetFrame = [self.view convertRect:dropTarget.frame fromView:dropTarget.superview];
        if (CGRectContainsPoint(convertedTargetFrame, dragView.center)) // if so, then drop it.
        {
            ImageWithAttachedLabel *i = (ImageWithAttachedLabel *) dragView;
            [speakStrings addObject:[i.labelText stringByAppendingString:@". "]];
            UserData *uData = (UserData *)i.userDataObject;
            UIImage *image = [[UIImage alloc] initWithData:uData.image];
            CGRect newFrame = CGRectMake(0.0f, 0.0f, 140.0f, 140.0f);
            ImageWithAttachedLabel *newImage = [[ImageWithAttachedLabel alloc] initWithFrame:newFrame withImage:image withLabel:uData.itemName];
            newImage.tag = RECEIVERVIEW_MAGIC_NUMBER;
            [self.view addSubview:newImage];
            newImage.center = [receiverView convertPoint:dropTarget.center toView:self.view];
            [UIView animateWithDuration:0.35f animations:^{ newImage.transform = CGAffineTransformMakeScale(1.15f, 1.15f); newImage.transform = CGAffineTransformIdentity; }
                             completion:^(BOOL finished) {  if (finished)
                                                            {
                                                                [newImage removeFromSuperview];
                                                                newImage.frame = newFrame;
                                                                [dropTarget addSubview:newImage];
                                                                [dragView removeFromSuperview];
                                                                dragView=nil; }
                                                            }];

        }
        else
        {
            [dragView removeFromSuperview];
            dragView = nil;
        }

        [self reloadData];
        return;
    }
}