NSView 没有收到 mouseUp: 鼠标按钮在视图外释放时的事件

Question

我有一个自定义的NSView 子类（例如）以下方法：

override func mouseDown(with event: NSEvent) { Swift.print("mouseDown") }
override func mouseDragged(with event: NSEvent) { Swift.print("mouseDragged") }
override func mouseUp(with event: NSEvent) { Swift.print("mouseUp") }

只要在视图内按下、拖动和释放鼠标（按钮），就可以正常工作。但是，当鼠标在视图内按下，移到视图外，然后才释放时，我从未收到mouseUp 事件。

P.S.：调用 super 实现没有帮助。

Answer 1

Apple 鼠标事件文档的 Handling Mouse Dragging Operations 部分提供了一个解决方案：显然，在使用鼠标跟踪循环跟踪事件时，我们确实收到了 mouseUp 事件。

这是文档中示例代码的变体，适用于 Swift 3：

override func mouseDown(with event: NSEvent) {
    var keepOn = true

    mouseDownImpl(with: event)

    // We need to use a mouse-tracking loop as otherwise mouseUp events are not delivered when the mouse button is
    // released outside the view.
    while true {
        guard let nextEvent = self.window?.nextEvent(matching: [.leftMouseUp, .leftMouseDragged]) else { continue }
        let mouseLocation = self.convert(nextEvent.locationInWindow, from: nil)
        let isInside = self.bounds.contains(mouseLocation)

        switch nextEvent.type {
        case .leftMouseDragged:
            if isInside {
                mouseDraggedImpl(with: nextEvent)
            }

        case .leftMouseUp:
            mouseUpImpl(with: nextEvent)
            return

        default: break
        }
    }
}

func mouseDownImpl(with event: NSEvent) { Swift.print("mouseDown") }
func mouseDraggedImpl(with event: NSEvent) { Swift.print("mouseDragged") }
func mouseUpImpl(with event: NSEvent) { Swift.print("mouseUp") }

Answer 2

我将此作为对我需要知道用户已停止使用滑块的类似问题的答案发布。我需要从 NSSlider 或实际上是 NSView 捕获 mouseUp 事件。为我解决的解决方案是简单地捕获 mouseDown 事件并在它退出时添加一些代码并完成我需要的工作。希望这对需要做类似事情的其他人有用。使用 XCode 11.3.1 Swift 5 编写的代码

import Cocoa

class SMSlider: NSSlider {

    var calledOnExit:(()->())?

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

    override func mouseDown(with event: NSEvent) {
        super.mouseDown(with: event)
        if self.calledOnExit != nil {
            self.calledOnExit!()
        }
    }    
}

// In my main swift app
func sliderStopped() {
    print("Slider stopped moving")
}

//...
if slider == nil {
    slider = SMSlider()
}
slider?.isContinuous = true
slider?.target = self
slider?.calledOnExit = sliderStopped
//...