Question

我有UICollectionView，我正在显示自定义单元格。我正在尝试通过长按手势移动单元格，但它根本不起作用。

我已经关注了this教程，但这对我没用。请告诉我该怎么做？

长按手势

-(void)handleLongPress:(UILongPressGestureRecognizer *)gestureRecognizer
{

    NSLog(@"long press geture called");
    switch(gestureRecognizer.state)
    {
        case UIGestureRecognizerStateBegan:
            p = [gestureRecognizer locationInView:self.collection_view];
          gesture_indexPath = [self.collection_view indexPathForItemAtPoint:p];
        [self.collection_view beginInteractiveMovementForItemAtIndexPath:gesture_indexPath];
            NSLog(@"state began called");

                     break;

        case UIGestureRecognizerStateChanged:

        //    collectionView.updateInteractiveMovementTargetPosition(gesture.locationInView(gesture.view!))
            [self.collection_view updateInteractiveMovementTargetPosition:[gestureRecognizer locationInView:[gestureRecognizer view]]];
            NSLog(@"state changed called");
        case UIGestureRecognizerStateEnded:
            [self.collection_view updateInteractiveMovementTargetPosition:p];
                  NSLog(@"state changed called");
        default:
            [self.collection_view cancelInteractiveMovement];
    }
}

方法覆盖

-(void)collectionView:(UICollectionView *)collectionView moveItemAtIndexPath:(NSIndexPath *)sourceIndexPath toIndexPath:(NSIndexPath *)destinationIndexPath
{
    NSLog(@"Move at index path called");
}

Answer 1

您在 switch-case 块中缺少break;个语句。如果每个 case 部分末尾没有break;，则不会退出switch-case语句，并执行下一行。

为了完整性，这里是Objective-C中可重新排序UICollectionView的最低实现。

为嵌入UICollectionView内的UICollectionViewController 而不是实施重新排序（可能改为UIViewController内部，但可能位于UICollectionViewCell或{ {1}}如果你想得到的话，至少需要以下三个部分：

在UITableViewCell内（或者，如果您将viewDidLoad嵌入到故事板中设置的UICollectionView或UITableViewCell内，则此代码进入UICollectionViewCell），向awakeFromNib添加UILongPressGestureRecognizer，如下所示：
```
UICollectionView
```
实施UILongPressGestureRecognizer *longGR = [[UILongPressGestureRecognizer alloc] initWithTarget:self action:@selector(handleLongPress:) [self.yourCollectionView addGestureRecognizer:longGR];以对刚刚添加的handleLongPress:做出反应：
```
UILongPressGestureRecognizer
```

最后，添加以下内容：

- (void)handleLongPress:(UILongPressGestureRecognizer *)gr{   
    switch(gr.state){
        case UIGestureRecognizerStateBegan:
        {
            NSIndexPath *selectedIndexPath = [self.yourCollectionView indexPathForItemAtPoint:[gr locationInView:self.yourCollectionView]];
            if(selectedIndexPath == nil) break;
            [self.yourCollectionView beginInteractiveMovementForItemAtIndexPath:selectedIndexPath];
            break;
        }
        case UIGestureRecognizerStateChanged:
        {
            [self.yourCollectionView updateInteractiveMovementTargetPosition:[gr locationInView:gr.view]];
            break;
        }
        case UIGestureRecognizerStateEnded:
        {
            [self.yourCollectionView endInteractiveMovement];
            break;
        }
        default:
        {
            [self.yourCollectionView cancelInteractiveMovement];
            break;
        }
    }
}

....当你触摸，按住然后拖动时，细胞现在会神奇地移动！

（这都假设您已实施标准- (void)collectionView:(UICollectionView *)collectionView moveItemAtIndexPath:(NSIndexPath *)sourceIndexPath toIndexPath:(NSIndexPath *)destinationIndexPath{ //add your data source manipulation logic here //specifically, change the order of entries in the data source to match the new visual order of the cells. //even without anything inside this function, the cells will move visually if you build and run } dataSource 和委托方法，并且UICollectionView已成功加载/在您的应用中显示。如果您需要有关UICollectionView基本设置的帮助，请查看Warewolf的this post。

Answer 2

您的switch语句正在落空（将使用Swift编写的博客文章翻译成Objective-C的风险之一）。每次调用处理程序时触摸位置的变化都会执行Changed：case下面的每个语句，包括cancelInteractiveMovement（另一个注释，应该是endInteractiveMovement）。

无法通过移动它们重新排列UICollectionView中的单元格？

2 个答案: