NSCollectionView拖放：大多数代理事件未调用 [英] NSCollectionView Drag and Dropping: Most Delegate Events Not Getting Called

问题描述

我有一个NSCollectionView绑定到一个NSArrayController。我想要拖放工作，所以我创建一个委托并实现方法

   - （BOOL）collectionView：（NSCollectionView *）collectionView canDragItemsAtIndexes：（NSIndexSet *）index withEvent：（NSEvent *）event 
  - （BOOL）collectionView：（NSCollectionView *）collectionView acceptDrop：（id< NSDraggingInfo>）draggingInfo index：（NSInteger）index dropOperation （NSCollectionViewDropOperation）dropOperation 
  - （NSDragOperation）collectionView：（NSCollectionView *）collectionView validateDrop：（id< NSDraggingInfo>）draggingInfo proposedIndex：（NSInteger *）proposedDropIndex dropOperation：（NSCollectionViewDropOperation *）proposedDropOperation 
- （NSArray *）collectionView：（NSCollectionView *）collectionView namesOfPromisedFilesDroppedAtDestination :( NSURL *）dropURL forDraggedItemsAtIndexes：（NSIndexSet *）indexes 
  
 
 $ b b 
我为两个BOOL方法返回YES，对validateDrop：方法使用NSDragOperationMove，对namesOfPromisedFilesDroppedAtDestination：方法使用空数组。我也有一个NSLog语句作为第一行在每个方法，所以我可以看到，当他们被调用。 
 
 
 
现在，唯一可以调用的方法是canDragItemsAtIndexes：（其中我返回YES）。我看到它被调用，但任何进一步的拖动只是修改选择。其余的从未被调用。 
 
 
 
如果我使NSCollectionView不支持选择，那么甚至不调用该方法。 
 
 
 
我确定我错过了一些非常明显的东西，但我不知道它是什么。有谁得到拖放工作与NSCollectionViews和可以散发一些光？ 
解决方案
我想你错过了将粘贴内容写入粘贴板的部分。
 
您必须执行以下步骤：
 
 
确定是否可以拖动拖动源
 
 
如果是，请将内容写入粘贴板
 
 
验证&接受您的放置目标中的项目
 
 
写入粘贴板应在
中实现
    -  collectionView：writeItemsAtIndexes：toPasteboard：  
 
 
 
您还必须注册拖动的类型   -  registerForDraggedTypes：  
 
 
 
一些示例代码：
  http://developer.apple.com/library/mac/ ＃samplecode / IconCollection / Introduction / Intro.html  
 
I have an NSCollectionView bound to an NSArrayController. I want to get drag and drop working, so I create a delegate and implement the methods 
-(BOOL)collectionView:(NSCollectionView *)collectionView canDragItemsAtIndexes:(NSIndexSet *)indexes withEvent:(NSEvent*)event
-(BOOL)collectionView:(NSCollectionView *)collectionView acceptDrop:(id < NSDraggingInfo >)draggingInfo index:(NSInteger)index dropOperation:(NSCollectionViewDropOperation)dropOperation
-(NSDragOperation)collectionView:(NSCollectionView *)collectionView validateDrop:(id < NSDraggingInfo >)draggingInfo proposedIndex:(NSInteger *)proposedDropIndex dropOperation:(NSCollectionViewDropOperation *)proposedDropOperation
-(NSArray *)collectionView:(NSCollectionView *)collectionView namesOfPromisedFilesDroppedAtDestination:(NSURL *)dropURL forDraggedItemsAtIndexes:(NSIndexSet *)indexes
I'm returning YES for the two BOOL methods, NSDragOperationMove for the validateDrop: method, and an empty array for the namesOfPromisedFilesDroppedAtDestination: method. I also have an NSLog statement as the first line in each method so I can see when they get called. 

Right now, the only method that gets called is canDragItemsAtIndexes: (where I return YES). I see that it gets called, but any further dragging just modifies the selection. The rest never get called. 

If I make the NSCollectionView not support selections, then not even that method gets called. 

I'm sure I'm missing something super obvious, but I can't figure out what it is. Has anyone gotten drag and drop working with NSCollectionViews and can shed some light? 
解决方案
I think you miss the part where you write the drag content to the pasteboard.

To support drag and drop you have to perform the following steps:  

Determine if you can drag in your drag source
If YES, write the content to the Pasteboard
Validate & accept the items in your drop target
Writing to the Pasteboard should be implemented in

- collectionView:writeItemsAtIndexes:toPasteboard:

You also have to register your dragged types with - registerForDraggedTypes:

Some sample code:
http://developer.apple.com/library/mac/#samplecode/IconCollection/Introduction/Intro.html

                        
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