ios - 无法通过移动它们来重新排列 UICollectionView 中的单元格？

Question

我有 UICollectionView 我在其上显示 定制 细胞。我试图通过长按手势来移动细胞，但它根本不起作用。

我关注了this教程，但它对我不起作用。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

你错过了break; switch-case block 中的语句。没有 break;在每个 case 部分的末尾，不退出 switch-case 语句，而是执行下一行。

为了完整起见，这里是 Objective-C 中用于可重新排序的 UICollectionView 的最低实现。 .

为 UICollectionView 实现重新排序不是 嵌入到 UICollectionViewController (可能是在 UIViewController 内，但也可能在 UICollectionViewCell 或 UITableViewCell 内，如果你喜欢的话)至少需要以下三个部分:

内部 viewDidLoad (或者，如果您将 UICollectionView 嵌入到 UITableViewCell 或 UICollectionViewCell 在 Storyboard 中设置，则此代码将进入 awakeFromNib )，添加 UILongPressGestureRecognizer给您的UICollectionView像这样:

UILongPressGestureRecognizer *longGR = [[UILongPressGestureRecognizer alloc] initWithTarget:self action:@selector(handleLongPress:)
[self.yourCollectionView addGestureRecognizer:longGR];

实现handleLongPress:对 UILongPressGestureRecognizer 使用react您刚刚添加:

- (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;
        }
    }
}

最后，添加以下内容:

- (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

}

....当您触摸、按住、拖动时，细胞现在会神奇地移动!

(这一切都假设您已经实现了标准的 UICollectionView 数据源和委托(delegate)方法，并且 UICollectionView 已成功加载/显示在您的应用程序中。如果您需要有关 UICollectionView 的基本设置的帮助，请查看this post 作者:狼人)。