如何通过两次鼠标单击（OSX Mac App）编码绘制一条直线？

Question

我正在尝试制作一个简单的绘图应用程序（OSX Mac 应用程序），并且我试图弄清楚用户如何通过两次鼠标单击来绘制一条线，例如，第一次鼠标单击（mouseDown 然后 mouseUP）将标记线的起点，第二次鼠标单击（mouseDown 然后 mouseUP）将标记线的终点。在用户第二次单击终点之前，我希望线（在锚定终点之前）实时显示，有点像在 Photoshop 中。 Objective-C 和 Swift 都很好。

到目前为止，我已经...

var newLinear = NSBezierPath()

override func mouseDown(theEvent: NSEvent) {
        super.mouseDown(theEvent)
        var lastPoint = theEvent.locationInWindow
        lastPoint.x -= frame.origin.x
        lastPoint.y -= frame.origin.y
        newLinear.moveToPoint(lastPoint)
    }

override func mouseUp(theEvent: NSEvent) {
        var newPoint = theEvent.locationInWindow
        newPoint.x -= frame.origin.x
        newPoint.y -= frame.origin.y
        newLinear.lineToPoint(newPoint)
        needsDisplay = true
    }

干杯！

Answer 1

带有关联值的enums 非常适合您的应用程序扩展并可能添加其他工具和状态。

enum State {
    case normal
    case drawingLine(from: CGPoint, to: CGPoint)
}
var state = State.normal

override func mouseDown(theEvent: NSEvent) {
    super.mouseDown(theEvent)
    var lastPoint = theEvent.locationInWindow
    lastPoint.x -= frame.origin.x
    lastPoint.y -= frame.origin.y
    state = .drawingLine(from: lastPoint, to: lastPoint)
}

override func mouseUp(theEvent: NSEvent) {
    if case .drawingLine(let firstPoint, _) = state {
        var newPoint = theEvent.locationInWindow
        newPoint.x -= frame.origin.x
        newPoint.y -= frame.origin.y
        //finalize line from `firstPoint` to `newPoint`
    }
}

override func mouseMoved(theEvent: NSEvent) {
    if case .drawingLine(let firstPoint, _) = state {
        needsDisplay = true
        var newPoint = theEvent.locationInWindow
        newPoint.x -= frame.origin.x
        newPoint.y -= frame.origin.y
        state = .drawingLine(from: firstPoint, to: newPoint)
    }
}

override func draw(_ dirtyRect: NSRect) {
    if case .drawingLine(let firstPoint, let secondPoint) = state {
        //draw your line from `firstPoint` to `secondPoint`
    }
}

Answer 2

我了解您在这里尝试实现的目标！因此，我在 andyvn22 的解决方案中添加了几行代码，这应该有助于您的工作，请注意：为简单起见，开始一个新的“Xcode 项目”，我们可以确保所有内容都包含在一起。

在您的新项目中右键单击“ViewController.swift”并添加新文件...选择“Cocoa Class”并单击“下一步”，将此文件命名为“DrawingView”，确保子类为“NSView”并选择“下一步”。

现在您已完成设置界面，输入“Main.storyboard”并拖放“自定义视图”，确保根据您的偏好添加约束。现在输入您的“Identity Inspector”，同时选择“Custom View”并将“DrawingView”添加到顶部的 Class。

我希望到目前为止这是有道理的！好的，打开“Assistant Editor”，这样您就可以同时查看“ViewController.swift”和“Main.storyboard”，右键单击并从“Custom View”拖动到“ViewController.swift”，将其命名为“draw”并选择“connect”。

您会注意到 Xcode 已自动将 @IBOutlet 更新为您的子类，并且您的“ViewController.swift”看起来像下面的示例。

import Cocoa

class ViewController: NSViewController {

    @IBOutlet var draw: DrawingView!

    override func viewDidLoad() {
        super.viewDidLoad()

        // Do any additional setup after loading the view.
    }

    override var representedObject: Any? {
        didSet {
        // Update the view, if already loaded.
        }
    }
}

现在选择“DrawingView.swift”文件并清除页面上的所有内容，突出显示下面的代码，复制并粘贴到您的项目中。

import Cocoa

class DrawingView: NSView {

    // >>>CODE ADDED BY LC<<<
    private var path: NSBezierPath = {
        let path = NSBezierPath()
        path.lineWidth = 50.0
        path.lineJoinStyle = .roundLineJoinStyle
        path.lineCapStyle = .roundLineCapStyle
        return path
    }()

    enum State {
        case normal
        case drawingLine(from: CGPoint, to: CGPoint)
    }
    var state = State.normal

    override func mouseDown(with event: NSEvent) {
        super.mouseDown(with: event)
        var lastPoint = event.locationInWindow
        lastPoint.x -= frame.origin.x
        lastPoint.y -= frame.origin.y
        state = .drawingLine(from: lastPoint, to: lastPoint)
    }

    override func mouseUp(with event: NSEvent) {
        if case .drawingLine(let firstPoint, _) = state {
            var newPoint = event.locationInWindow
            newPoint.x -= frame.origin.x
            newPoint.y -= frame.origin.y

            // >>>CODE ADDED BY LC<<<
            path.move(to: convert(event.locationInWindow, from: nil))
            path.line(to: firstPoint)
            needsDisplay = true
        }
    }

    override func draw(_ dirtyRect: NSRect) {
        if case .drawingLine(let firstPoint, let secondPoint) = state {

            // >>>CODE ADDED BY LC<<<
            NSColor.orange.set()
            path.lineWidth = 5.0
            path.stroke()
            path.line(to: firstPoint)
            path.line(to: secondPoint)
        }
    }
}

一切都应该按预期运行，您将无法画出一条弯曲的线。我希望这对您有所帮助，并随时回复以获取更多信息。