JavaFX中Scene的KeyPressed事件回调被触发两次的问题

问题现象 #

• 焦点在TextField上时，onKeyPressed绑定的方法会被调用两次；
• 焦点在不可编辑组件（如Button）上时，该方法仅被调用一次。

调试信息 #

在调用selectBack()方法的第181行设置断点后，发现两次调用均来自Scene的同一事件。

复现环境 #

Java11（jdk-11.0.11）+JavaFX11（javafx-sdk-11.0.2）

项目结构 #

Test
|
+-src
   |
   +-application
   |         |
   |         +--Controller.java
   |         |
   |         +--Main.java
   |         |
   |         +--Test.fxml
   |
   module-info.java

代码文件 #

Main.java

package application;

import javafx.application.Application;
import javafx.fxml.FXMLLoader;
import javafx.stage.Stage;
import javafx.scene.Scene;
import javafx.scene.layout.AnchorPane;

public class Main extends Application {
    @Override
    public void start(Stage stage){
        try {
            FXMLLoader loader = new FXMLLoader(Main.class.getResource("Test.fxml"));
            AnchorPane root = (AnchorPane) loader.load();
            Scene scene = new Scene(root);
            stage.setTitle("Test");
            stage.setScene(scene);
            stage.show();
            
        }
        catch(Exception e) {
            e.printStackTrace();
        }
    }
    
    public static void main(String[] args) {
        launch(args);
    }
}

Controller.java

package application;

import javafx.application.Platform;
import javafx.event.ActionEvent;
import javafx.fxml.FXML;
import javafx.scene.control.Alert;
import javafx.scene.control.Alert.AlertType;
import javafx.scene.input.KeyCode;
import javafx.scene.layout.AnchorPane;

public class Controller {
    @FXML
    private AnchorPane base;
    private int counter = 0;

    public void initialize()
    {
        Platform.runLater(() -> {
            this.base.getScene().setOnKeyPressed(e -> {
                if(e.getCode() == KeyCode.ESCAPE)
                    test(new ActionEvent());
            });
        });
        
    }
    
    @FXML private void move(ActionEvent event)
    {
    }
    
    @FXML private void test(ActionEvent event)
    {
        System.out.println("Counter: " + counter + " (" + System.currentTimeMillis() + ")");
        
        Alert alert = new Alert(AlertType.INFORMATION, "Test");
        alert.setContentText("Counter: " + counter);
        alert.showAndWait();
        
        counter++;
    }
}

Test.fxml

<?xml version="1.0" encoding="UTF-8"?>

<?import javafx.scene.control.Button?>
<?import javafx.scene.control.TextField?>
<?import javafx.scene.layout.AnchorPane?>

<AnchorPane id="base" fx:id="base" prefHeight="400.0" prefWidth="400.0" xmlns="http://javafx.com/javafx/18" xmlns:fx="http://javafx.com/fxml/1" fx:controller="application.Controller">
   <children>
      <TextField layoutX="125.0" layoutY="187.0" />
      <Button layoutX="174.0" layoutY="273.0" mnemonicParsing="false" text="Button" />
   </children>
</AnchorPane>

module-info.java

module test {
    requires javafx.controls;
    requires javafx.fxml;
    requires transitive javafx.base;
    requires transitive javafx.graphics;
    
    opens application;
}

运行配置VM参数 #

--module-path "bin;C:\Program Files\Java\javafx-sdk-11.0.2\lib" -m test/application.Main

复现步骤 #

运行程序后按下ESC键：

• 焦点在TextField上时，会显示两次Alert；
• 焦点在Button上时，仅显示一次Alert。

内容的提问来源于stack exchange，提问作者mikyll98