从NSOutlineView中拖放

Question

我正在试图弄清楚如何在NSOutlineView中实现拖放到自身.

例如,我希望用户能够重新排序并嵌套和重新嵌套NSOutlineView中的项目,但我不需要能够从任何其他来源(如文件或其他视图)拖动项目.

我可以找到的所有示例都处理将项目拖动到NSOutlineView中,而不仅仅是在其自身内部并且看起来过于复杂.我认为这是可能的.

有人可以指出一些只处理这种情况的文档吗？也许我只是错过了显而易见的事实.

Answer 1

我发现这个文档有点不清楚,除此之外,还有新的方法在Lion中添加.

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        
}

对于最后一种方法,需要填写大量代码,对于动画运动,在samir的注释中提到的Apple的复杂表格视图演示代码非常有用,如果解密有些复杂的话.

Answer 2

我创建了一个小样本项目它有一个NSOutlineView在这里你可以添加和删除的项目.

今天我基于@Monolo的答案实现了拖放支持(参见更改).