cocoa - 从 NSOutlineView 中拖放

Question

我正在尝试弄清楚如何实现从 NSOutlineView 内部到其自身的拖放。

例如，我希望用户能够重新排序、嵌套和重新嵌套 NSOutlineView 中的项目，但我不需要能够从任何其他源(如文件或其他 View )拖动项目)。

我能找到的所有示例都涉及将项目拖动到 NSOutlineView 中，而不仅仅是在其内部，并且看起来过于复杂。我认为这是可能的。

有人可以指出一些处理这种情况的文档吗？也许我只是错过了显而易见的事情。

Answer 1

我发现这方面的文档有些不清楚，除其他外，Lion 中添加了新的方法。

假设您需要 10.7 或更高版本，那么这可能是您实现的框架:

在您的数据源/委托(delegate)类中，实现:

// A method to register the view for dragged items from itself. 
// Call it during initialization
-(void) enableDragNDrop
{
    [self.outlineView registerForDraggedTypes: [NSArray arrayWithObject: @"DragID"]];
}


- (id <NSPasteboardWriting>)outlineView:(NSOutlineView *)outlineView pasteboardWriterForItem:(id)item 
{
    // No dragging if <some condition isn't met>

    if ( dontDrag )  {
        return nil;
    }

    // With all the blocking conditions out of the way,
    // return a pasteboard writer.

    // Implement a uniqueStringRepresentation method (or similar)
    // in the classes that you use for your items.
    // If you have other ways to get a unique string representation
    // of your item, you can just use that.
    NSString *stringRep = [item uniqueStringRepresentation];

    NSPasteboardItem *pboardItem = [[NSPasteboardItem alloc] init];

    [pboardItem setString:stringRep forType: @"DragID"];

    return pboardItem;
}


- (NSDragOperation)outlineView:(NSOutlineView *)outlineView validateDrop:(id < NSDraggingInfo >)info proposedItem:(id)item proposedChildIndex:(NSInteger)index
{
    BOOL dragOK = // Figure out if your dragged item(s) can be dropped
                  // on the proposed item at the index given

    if ( dragOK ) {
        return NSDragOperationMove;
    }
    else {
        return NSDragOperationNone;
    }
}


- (BOOL)outlineView:(NSOutlineView *)outlineView acceptDrop:(id < NSDraggingInfo >)info item:(id)item childIndex:(NSInteger)index
{           
    // Move the dragged item(s) to their new position in the data model
    // and reload the view or move the rows in the view.
    // This is of course quite dependent on your implementation        
}

最后一个方法需要填写大量代码，关于动画运动，Apple 的 complex table view demo code萨米尔的评论中提到的非常有用，尽管解读起来有些复杂。