如何在Scalafx中创建两个场景

Question

我是使用Scalafx创建GUI的新手。我正在尝试使用以下代码创建两个场景，但是会遇到一些错误，

import com.sun.glass.ui.Application
import scalafx.event.ActionEvent
import scalafx.event.EventHandler
import scalafx.scene.Scene
import scalafx.scene.control.Button
import scalafx.scene.control.Label
import scalafx.scene.layout.StackPane
import scalafx.scene.layout.VBox
import scalafx.stage.Stage



class example extends Application {
  var scene1: Scene = null
  var scene2: Scene = null
  override def start(primaryStage: Stage): Unit =  { primaryStage.setTitle("My First JavaFX GUI")
    //Scene 1
    val label1 = new Label("This is the first scene")
    val button1 = new Button("Go to scene 2"){
      onAction = (e: ActionEvent) => {
        primaryStage.setScene(scene2)
      }
    }
    val layout1 = new VBox(20)
    layout1.getChildren.addAll(label1, button1)
    scene1 = new Scene(layout1, 300, 250)


    //Scene 2
    val label2 = new Label("This is the second scene")
    val button2 = new Button("Go to scene 1") {
      onAction = (e: ActionEvent) => {
        primaryStage.setScene(scene1)
      }
    }
    val layout2 = new VBox(20)
    layout2.getChildren.addAll(label2, button2)
    scene2 = new Scene(layout2, 300, 250)

    primaryStage.setScene(scene1)
    primaryStage.show()
  }
}

The error is:
 found   : scalafx.event.ActionEvent => Unit
[error]  required: javafx.event.EventHandler[javafx.event.ActionEvent]
[error]       onAction = (e: ActionEvent) => {}

如何声明在场景之间切换的操作事件？

如果有人能有所帮助，这真的很有帮助

Answer 1

在ScaleFX中，您的第一个故障排除是检查您是否包括ScaleFX隐式转换魔法：

import scalafx.Includes._

在您的情况下，这将解决动作处理程序的问题。

此外，您不应使用com.sun beackafx中的软件包和javafx代码中均不使用。在Scalafx中，您应该改用JFXAPP3。这是您的代码更正以使用JFXAPP3进行一些较小的更正：

import scalafx.Includes._
import scalafx.application.JFXApp3
import scalafx.application.JFXApp3.PrimaryStage
import scalafx.event.{ActionEvent, EventHandler}
import scalafx.scene.Scene
import scalafx.scene.control.{Button, Label}
import scalafx.scene.layout.VBox
import scalafx.stage.Stage

object CreteTwoScenes1App extends JFXApp3 {
  var scene1: Scene = _
  var scene2: Scene = _

  override def start(): Unit = {

    stage = new PrimaryStage {
      title = "My First JavaFX GUI"
    }

    // Scene 1
    val label1 = new Label("This is the first scene")
    val button1 = new Button("Go to scene 2") {
      onAction = (e: ActionEvent) => {
        stage.setScene(scene2)
      }
    }
    val layout1 = new VBox(20)
    layout1.children ++= Seq(label1, button1)

    scene1 = new Scene(layout1, 300, 250)

    // Scene 2
    val label2 = new Label("This is the second scene")
    val button2 = new Button("Go to scene 1") {
      onAction = (e: ActionEvent) => {
        stage.setScene(scene1)
      }
    }
    val layout2 = new VBox(20)
    layout2.children ++= Seq(label2, button2)
    scene2 = new Scene(layout2, 300, 250)

    stage.setScene(scene1)
  }
}

您还可以以更惯用的Scalafx构建器样式进行重写。使用Scala 3也可以使其变得更加紧凑（无需卷发）：

import scalafx.Includes.*
import scalafx.application.JFXApp3
import scalafx.scene.Scene
import scalafx.scene.control.{Button, Label}
import scalafx.scene.layout.VBox

object CreteTwoScenes2App extends JFXApp3:

  override def start(): Unit =
    lazy val scene1: Scene = new Scene(300, 200):
      root = new VBox(20):
        children = Seq(
          new Label("This is the first scene"),
          new Button("Go to scene 2"):
            onAction = () => stage.setScene(scene2)
        )

    lazy val scene2: Scene = new Scene(300, 200):
      root = new VBox(20):
        children = Seq(
          new Label("This is the second scene"),
          new Button("Go to scene 1"):
            onAction = () => stage.setScene(scene2)
        )

    stage = new JFXApp3.PrimaryStage:
      title = "My First JavaFX GUI"
      scene = scene1