ios - UICollectionView 单元格的水平重新排序

Question

我有一个水平滚动的 UICollectionView。每个单元格对应数组中的一个对象(货币代码)。我想要的是能够通过拖放手势对单元格重新排序。

我找到了一个 tutorial对于 UITableView 并尝试过，但是当我按住并拖动一个单元格时，它只会垂直移动，当我将手指移到屏幕边缘时它不会滚动。这是一个gif .

我想要发生的是让单元格水平移动，而不是垂直移动，并让 Collection View 在到达屏幕边缘时滚动。我将如何实现这一目标？

这是我现在拥有的:

UILongPressGestureRecognizer *longPress = [[UILongPressGestureRecognizer alloc] initWithTarget: self action: @selector(longPressGestureRecognised:)];
[self.collectionView addGestureRecognizer: longPress];


-(IBAction) longPressGestureRecognised:(id)sender
{
UILongPressGestureRecognizer *longPress = (UILongPressGestureRecognizer *)sender;
UIGestureRecognizerState state = longPress.state;

CGPoint location = [longPress locationInView: self.collectionView];
NSIndexPath *indexPath = [self.collectionView indexPathForItemAtPoint: location];

static UIView *snapshot = nil;
static NSIndexPath *sourceIndexPath = nil;

switch (state) {
    case UIGestureRecognizerStateBegan: {
        if (indexPath) {
            sourceIndexPath = indexPath;

            UICollectionViewCell *cell = [self.collectionView cellForItemAtIndexPath: indexPath];

            // Take a snapshot of the selected item using helper method.
            snapshot = [self customSnapshotFromView: cell];

            // Add the snapshot as subview, centered at cell's centre.
            __block CGPoint centre = cell.center;
            snapshot.center = centre;
            snapshot.alpha = 0.0;
            [self.collectionView addSubview: snapshot];
            [UIView animateWithDuration: 0.25 animations:^{

                // Offset for gesture location.
                centre.y = location.y;
                snapshot.center = centre;
                snapshot.transform = CGAffineTransformMakeScale(1.05, 1.05);
                snapshot.alpha = 0.98;

                // Fade out.
                cell.alpha = 0.0;

            } completion: ^(BOOL finished) {
                cell.hidden = YES;
            }];
        }
        break;
    }

    case UIGestureRecognizerStateChanged: {
        CGPoint centre = snapshot.center;
        centre.y = location.y;
        snapshot.center = centre;

        // Is destination valid and is it different from source?
        if (indexPath && ![indexPath isEqual: sourceIndexPath]) {
            // Update data source.
            [currencyArray exchangeObjectAtIndex: indexPath.item withObjectAtIndex:sourceIndexPath.item];

            // Move the items.
            [self.collectionView moveItemAtIndexPath: sourceIndexPath toIndexPath: indexPath];

            // And update source so it is in sync with UI changes.
            sourceIndexPath = indexPath;
        }
        break;
    }

    default: {
        // Clean up.
        UICollectionViewCell *cell = [self.collectionView cellForItemAtIndexPath: sourceIndexPath];
        cell.hidden = NO;
        cell.alpha = 0.0;
        [UIView animateWithDuration: 0.25 animations: ^{

            snapshot.center = cell.center;
            snapshot.transform = CGAffineTransformIdentity;
            snapshot.alpha = 0.0;

            // Undo fade out.
            cell.alpha = 1.0;

        }completion: ^(BOOL finished) {

            sourceIndexPath = nil;
            [snapshot removeFromSuperview];
            snapshot = nil;

        }];
        break;
    }
}
}


-(UIView *) customSnapshotFromView:(UIView *)inputView
{
// Make an image from the input view.
UIGraphicsBeginImageContextWithOptions(inputView.bounds.size, NO, 0);
[inputView.layer renderInContext: UIGraphicsGetCurrentContext()];
UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();

// Create an image view.
UIView *snapshot = [[UIImageView alloc] initWithImage: image];
snapshot.layer.masksToBounds = NO;
snapshot.layer.cornerRadius = 0.0;
snapshot.layer.shadowOffset = CGSizeMake(-5.0, 0.0);
snapshot.layer.shadowRadius = 5.0;
snapshot.layer.shadowOpacity = 0.4;

return snapshot;
}

编辑:我想通了。这是代码:

UILongPressGestureRecognizer *longPress = [[UILongPressGestureRecognizer alloc] initWithTarget: self action: @selector(handleLongGesture:)];
[self.collectionView addGestureRecognizer: longPress];

-(IBAction) handleLongGesture: (id)sender {
UILongPressGestureRecognizer *longPress = (UILongPressGestureRecognizer *)sender;

CGPoint location = [longPress locationInView: self.collectionView];
NSIndexPath *indexPath = [self.collectionView indexPathForItemAtPoint: location];

switch (longPress.state) {
    case UIGestureRecognizerStateBegan:
        [self.collectionView beginInteractiveMovementForItemAtIndexPath: indexPath];
        NSLog(@"Gesture began");
        break;

    case UIGestureRecognizerStateChanged:
        [self.collectionView updateInteractiveMovementTargetPosition: [longPress locationInView: longPress.view]];
        NSLog(@"Gesture state changed");
        break;

    case UIGestureRecognizerStateEnded:
        [self.collectionView endInteractiveMovement];
        NSLog(@"Gesture state ended");
        break;

    default:
        [self.collectionView cancelInteractiveMovement];
        NSLog(@"Gesture cancelled");
        break;
    }
}

Answer 1

在 UIGestureRecognizerStateChanged 中:更改这行代码

        CGPoint centre = snapshot.center;
        centre.x = location.x;
        snapshot.center = centre;

centre.y 返回 y 轴拖动

将其更改为center.x用于x轴拖动