将可拖动的 NSView 与 SwiftUI 组件结合使用时出现问题答案

【问题标题】：Problem combining a draggable NSView with SwiftUI components将可拖动的 NSView 与 SwiftUI 组件结合使用时出现问题
【发布时间】：2019-11-14 19:49:14
【问题描述】：

我有一个使用 Cocoa 编写的 NSView 类：

import Cocoa
import SwiftUI

final class EntityViewImpl: NSViewRepresentable {

    func makeNSView(context: NSViewRepresentableContext<EntityViewImpl>) -> EntityView {
        return EntityView(frame: NSRect(x: 0, y: 0, width: 100, height: 200))
    }

    func updateNSView(_ nsView: EntityView, context: NSViewRepresentableContext<EntityViewImpl>) {
        // do nothing
    }
}

class EntityView: NSView {

    var oldMousePosition: NSPoint = .zero
    var oldFrameOrigin: NSPoint = .zero

    override func draw(_ dirtyRect: NSRect) {
        super.draw(dirtyRect)

        NSColor.white.setFill()
        dirtyRect.fill()
    }

    override func mouseDown(with event: NSEvent) {
        self.oldFrameOrigin = self.frame.origin
        self.oldMousePosition = event.locationInWindow
    }

    override func mouseDragged(with event: NSEvent) {
        let pointInSuperview = event.locationInWindow
        self.frame.origin = NSPoint(x: oldFrameOrigin.x + (pointInSuperview.x - oldMousePosition.x),
                                    y: oldFrameOrigin.y + (pointInSuperview.y - oldMousePosition.y))
    }
}

我想在 SwiftUI 视图体中使用此类：

struct ContentView: View {

    var body: some View {
        Group {
            EntityViewImpl()
                .frame(width: 100, height: 100)
        }
        .frame(maxWidth: .infinity, maxHeight: .infinity)
    }

}

这很好用，我也可以在EntityView 周围拖动。但是，我只能在它的原始框架内“抓住”它。如果我将它拖到边界之外，鼠标事件将不再在原始框架之外的视图部分触发。我是否必须以某种方式“告诉” NSView 移动的 ContentView？

【问题讨论】：

标签： swift macos swiftui nsview

【解决方案1】：

其实如果你使用的是SwiftUI，你需要移动EntityView的superview，像这样：

override func mouseDown(with event: NSEvent) {
    self.oldFrameOrigin = self.superview!.frame.origin
    self.oldMousePosition = self.superview!.convert(event.locationInWindow, from: self)
}

override func mouseDragged(with event: NSEvent) {
    let pointInSuperview = self.superview!.convert(event.locationInWindow, from: self)
    self.superview!.frame.origin = NSPoint(x: oldFrameOrigin.x + (pointInSuperview.x - oldMousePosition.x),
                                y: oldFrameOrigin.y + (-pointInSuperview.y + oldMousePosition.y))
}

【讨论】：