Question

我的应用中有NSTableView和NSOutlineView。用户应该能够将项目从大纲视图拖动到表格视图;如果它是可接受的操作（即所选行索引在粘贴板中），则表视图的目标行亮起。除了最初将项目拖入表格视图时，一切都有效。

接收表中的每个NSTableCellView都有以下方法：

func dragContainsIndices(pasteboard: NSPasteboard) -> IndexSet {
        if let types:[String] = pasteboard.types {
            for type in types {
                if type == BTVPBoardType { //_1
                    if let indexData: Data = pasteboard.data(forType: BTVPBoardType) {. //_2
                        let indicies: IndexSet = NSKeyedUnarchiver.unarchiveObject(with: indexData) as! IndexSet
                        if indicies.count > 0 {
                            return indicies
                        }
                    }
                }
            }
        }
        return IndexSet()
    }

override func draggingEntered(_ sender: NSDraggingInfo) -> NSDragOperation {
        let pastboard: NSPasteboard = sender.draggingPasteboard()
        if self.dragContainsIndices(pasteboard: pastboard).count > 0 {
            self.backingIcon.imageColour = .darkGreen //proprietary background colouring method
        }
        return  .link
    }

如果用户尝试将行从大纲视图拖到表格视图，则表格单元格视图中的draggingEntered(_:)会运行，但dragContainsIndices(_:)无法识别NSPasteboard拥有任何数据，即使它包含正确的type。 //_1处的检查通过，但代码未找到任何数据。因此它返回一个空集，导致背景颜色不被更改。

如果没有发布任何内容，如果用户将该项目拖离单元格然后再返回该单元格，那么索引集将正确展开并且颜色会发生变化。

在NSTableView中，我使用theses方法提供了拖动会话：

override func mouseDragged(with event: NSEvent) {
        let mouseDown    = self.mouseDownEvent.locationInWindow
        let dragPoint    = event.locationInWindow
        let dragDistance = hypot(mouseDown.x - dragPoint.x, mouseDown.y - dragPoint.y)

        if dragDistance < 3 || self.selectedRowIndexes.count < 1 {
            return
        }

        let pboardItem: NSPasteboardItem = NSPasteboardItem()
        if pboardItem.setDataProvider(self, forTypes: [BTVPBoardType]) {
            Swift.print ("Set data")
        }
        let dragItem: NSDraggingItem = NSDraggingItem(pasteboardWriter: pboardItem)
        var dragPos = self.convert(event.locationInWindow, from: nil)
        dragImage = NSImage.init(named: NSImageNameMultipleDocuments)!
        dragPos.x += dragImage.size.width
        dragPos.y += dragImage.size.height
        dragItem.imageComponentsProvider = {
            let component = NSDraggingImageComponent(key: NSDraggingImageComponentIconKey)
            component.contents = self.dragImage
            component.frame = NSRect(origin: NSPoint(), size: self.dragImage.size)
            return [component]
        }
        beginDraggingSession(with: [dragItem], event: event, source: self)
    }

func pasteboard(_ pasteboard: NSPasteboard?, item: NSPasteboardItem, provideDataForType type: String) {
        if files.count < 1 {return} //don't bother if there's no 
        if let pasteboard = pasteboard {
            pasteboard.declareTypes([BTVPBoardType], owner: self)
            let _: Int = pasteboard.clearContents()
            let indices = self.selectedRowIndexes
            pasteboard.setData(NSKeyedArchiver.archivedData(withRootObject: indices), forType: BTVPBoardType)
            Swift.print("written objects") //always writes indices
        }
    }

pasteboard(_ pasteboard: NSPasteboard?, item: NSPasteboardItem, provideDataForType type: String)是否与延迟抓取有关？出于某种原因，我在Mac上有一个拖拽和拖放的头部障碍。

第一次启动应用程序时，Cocoa拖放功能不起作用

0 个答案: