以 NSTableView 作为拖动源的自定义拖动图像

问题描述

当tableView为拖拽源时，是否需要继承NSTableView或NSTableCellView创建自定义拖拽图片?

Is it necessary to subclass NSTableView or NSTableCellView to create a custom drag image when the tableView is the drag source?

如果不是，我缺少什么神奇的方法来做到这一点?我似乎找不到任何可靠的东西.

If not, what is the magic method I am missing to do this? I cannot seem to find anything solid.

NSTableCellView 子类可以(有点神秘地)覆盖:

NSTableCellView subclasses have can (slightly mysteriously) override:

@property(retain, readonly) NSArray *draggingImageComponents(将组合在一起的 NSDraggingImageComponent 实例数组(谁知道它们以何种方式组合...)

@property(retain, readonly) NSArray *draggingImageComponents(array of NSDraggingImageComponent instances that will get composited together (who knows in what fashion they get composited...))

NSTableView本身有

- (NSImage *)dragImageForRowsWithIndexes:(NSIndexSet *)dragRows tableColumns:(NSArray *)tableColumns event:(NSEvent *)dragEvent offset:(NSPointPointer)dragImageOffset

但这些看起来确实是子类化选项.

But these are indeed subclassing options it seems.

这里有人知道另一种技术吗?(10.8+是目标)

Anybody know another technique here?(10.8+ is target )

推荐答案

好像NSTableViewCell

@property(retain, readonly) NSArray *draggingImageComponents

不会自动调用，但必须为基于视图的表视图显式引用.-draggingImageComponents 可以被覆盖以提供用于合成拖动图像的组件.

does not get called automatically but must be explicitly referenced for view based table views. -draggingImageComponents can be overridden to supply the components used to composite the drag image.

- (void)tableView:(NSTableView *)tableView draggingSession:(NSDraggingSession *)session willBeginAtPoint:(NSPoint)screenPoint forRowIndexes:(NSIndexSet *)rowIndexes
{
    // configure the drag image
    // we are only dragging one item - changes will be required to handle multiple drag items
    BPPopupButtonTableCellView *cellView = [self.columnsTableView viewAtColumn:0 row:rowIndexes.firstIndex makeIfNecessary:NO];
    if (cellView) {

        [session enumerateDraggingItemsWithOptions:NSDraggingItemEnumerationConcurrent
                                           forView:tableView
                                           classes:[NSArray arrayWithObject:[NSPasteboardItem class]]
                                     searchOptions:nil
                                        usingBlock:^(NSDraggingItem *draggingItem, NSInteger idx, BOOL *stop)
         {
             // we can set the drag image directly
             //[draggingItem setDraggingFrame:NSMakeRect(0, 0, myWidth, myHeight) contents:myFunkyDragImage];

             // the tableview will grab the entire table cell view bounds as its image by default.
             // we can override NSTableCellView -draggingImageComponents
             // which defaults to only including the image and text fields
             draggingItem.imageComponentsProvider = ^NSArray*(void) { return cellView.draggingImageComponents;};
         }];
    }
}

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