Javafx KeyEvent 和 MouseEvent

Question

我正在尝试学习 javafx。我完成了大部分代码，但我在使用 start 方法时遇到了问题。

我想做的是通过点击在屏幕上添加点。如果我按下 1 或 0，未来将添加的点将变为某种不同的颜色。因此，我知道我必须使用setOnMouseClicked 和setOnKeyPressed 方法，但互联网上没有太多关于它的内容。

import javafx.application.Application;
import javafx.stage.Stage;
import javafx.scene.Group;
import javafx.scene.Scene;
import javafx.scene.paint.Color;
import javafx.scene.shape.Circle;


public class Spots extends Application {

    public static final int SIZE = 500;    
    public static final int SPOT_RADIUS = 20;    
    private LinkedList<Spot> spotList;    
    private Color color;

    public static void main(String...args) {
        launch(args);
    }

    public void start(Stage stage) {

        stage.setTitle("Spots");    
        dotList = new SinglyLinkedList<>();        
        Group root = new Group();
        Scene scene = new Scene(root, 500, 500, Color.BLACK);
        Spot r;

        // ...    

        stage.show(); 
    }

    private class Spot extends Circle {

        public Spot(double xPos, double yPos) {
            super(xPos, yPos, SPOT_RADIUS);
            setFill(color);
        }

        public boolean contains(double xPos, double yPos) {
            double dx = xPos - getCenterX();
            double dy = yPos - getCenterY();
            double distance = Math.sqrt(Math.pow(dx, 2) + Math.pow(dy, 2));
            return distance <= SPOT_RADIUS;
        }        
    }
}

Answer 1

圈子不接受的原因是它没有专注。对于响应关键事件的节点，它们应该是focusTraversable。你可以这样做 在节点上调用 setFocusTraversable(true)。我编辑了你的 start() 方法，这是我最终得到的代码。

public void start(Stage primaryStage) throws Exception {

    Pane pane = new Pane();
    final Scene scene = new Scene(pane, 500, 500);
    final Circle circle = new Circle(250, 250, 20);
    circle.setFill(Color.WHITE);
   circle.setStroke(Color.BLACK);
    pane.getChildren().add(circle);
     circle.setFocusTraversable(true);
    circle.setOnKeyPressed(new EventHandler<KeyEvent>() {
        @Override
        public void handle(KeyEvent e) {
            if ((e.getCode() == KeyCode.UP) && (circle.getCenterY() >= 5)) {
                circle.setCenterY(circle.getCenterY() - 5);
            }

            else if ((e.getCode() == KeyCode.DOWN && (circle.getCenterY() <= scene.getHeight() - 5))) {
                circle.setCenterY(circle.getCenterY() + 5);
            }
            else if ((e.getCode() == KeyCode.RIGHT) && (circle.getCenterX() <= scene.getWidth() - 5)) {
                circle.setCenterX(circle.getCenterX() + 5);
            }
            else if ((e.getCode() == KeyCode.LEFT && (circle.getCenterX() >= 5))) {

                circle.setCenterX(circle.getCenterX()-5);
            }
        }
    });

  //creates new spots by clicking anywhere on the pane
    pane.setOnMouseClicked(new EventHandler<MouseEvent>() {  
      public void handle(MouseEvent event) {
            double newX = event.getX(); //getting the x-coordinate of the clicked area
            double newY = event.getY(); //getting the y-coordinate of the clicked area

            Circle newSpot = new Circle(newX, newY,20);
            newSpot.setFill(Color.WHITE);
            newSpot.setStroke(Color.BLACK);
            pane.getChildren().add(newSpot);

        }
    });

    primaryStage.setTitle("Move the circle");
    primaryStage.setScene(scene);
    primaryStage.show();
}

还请查看以下链接的答案：

• Handling keyboard events
• Cannot listen to KeyEvent in JavaFX

Answer 2

解决方法

您可以监控场景中的关键类型事件，并据此切换颜色模式。您可以在场景根窗格中放置一个鼠标事件处理程序，并在用户单击窗格中的任意位置时向场景添加一个圆圈（具有适合主要颜色模式的颜色）。

示例代码

import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.layout.Pane;
import javafx.scene.paint.Color;
import javafx.scene.shape.Circle;
import javafx.stage.Stage;

// Java 8+ code.
public class Spots extends Application {

    private static final int SIZE = 500;
    private static final int SPOT_RADIUS = 20;

    private Color color = Color.BLUE;

    public void start(Stage stage) {
        Pane root = new Pane();

        root.setOnMouseClicked(event ->
                root.getChildren().add(
                        new Spot(
                                event.getX(),
                                event.getY(),
                                color
                        )
                )
        );

        Scene scene = new Scene(root, SIZE, SIZE, Color.BLACK);
        scene.setOnKeyTyped(event -> {
            switch (event.getCharacter()) {
                case "0":
                    color = Color.BLUE;
                    break;
                case "1":
                    color = Color.RED;
                    break;
            }
        });

        stage.setScene(scene);
        stage.show();
    }

    private class Spot extends Circle {
        public Spot(double xPos, double yPos, Color color) {
            super(xPos, yPos, SPOT_RADIUS);
            setFill(color);
        }
    }

    public static void main(String... args) {
        launch(args);
    }
}

更多信息

• 有关 JavaFX 中事件处理的详细信息，请参阅Oracle JavaFX event tutorial。

Answer 3

通常，您会使用setOnAction，如Oracle tutorials 所示。

例子：

    btn.setOnAction(new EventHandler<ActionEvent>() {

        public void handle(ActionEvent event) {
            System.out.println("Hello World");
        }
    });

如果您尝试使用的特定节点没有 clickHandler 方法，请尝试执行以下操作（例如在 Group 上）：

    group.addEventHandler(MouseEvent.MOUSE_CLICKED, new EventHandler<MouseEvent>() {
        @Override
        public void handle(MouseEvent event) {
            System.out.println("Hello!");
        }
    });