从ViewModel TornadoFX绘制线条

import javafx.scene.paint.Color
import tornadofx.*

class LineViewModel : ViewModel() {
    val startXProperty = doubleProperty()
    var startX by startXProperty

    val startYProperty = doubleProperty()
    var startY by startYProperty

    val endXProperty = doubleProperty()
    var endX by endXProperty

    val endYProperty = doubleProperty()
    var endY by endYProperty

    val lineColorProperty = objectProperty<Color>()
    var lineColor by lineColorProperty

    fun drawLine(graphicsContext: GraphicsContext) {
        graphicsContext.stroke = lineColor
        graphicsContext.lineWidth = 2.0
        graphicsContext.strokeLine(startX, startY, endX, endY)
    }
}

class LineView : View() {
    val lineViewModel: LineViewModel by inject()

    override val root = vbox {
        val canvas = canvas(width = 400.0, height = 400.0)
        val graphicsContext = canvas.graphicsContext2D

        bind(lineViewModel.startXProperty, canvas.setOnMousePressed { lineViewModel.startX = it.x })
        bind(lineViewModel.startYProperty, canvas.setOnMousePressed { lineViewModel.startY = it.y })
        bind(lineViewModel.endXProperty, canvas.setOnMouseReleased { lineViewModel.endX = it.x })
        bind(lineViewModel.endYProperty, canvas.setOnMouseReleased { lineViewModel.endY = it.y })

        hbox {
            label("Line Color:")
            colorpicker().bind(lineViewModel.lineColorProperty)
        }

        button("Draw Line") {
            action { lineViewModel.drawLine(graphicsContext) }
        }
    }
}

class LineApp : App(LineView::class)

fun main() {
    launch<LineApp>()
}