Question

我有javafx gui运动要做，我必须使球向上或向下或左右移动。现在球在我想的任何地方随机出现。你能帮我解决一下代码吗？因此，当我按下加号按钮时，会添加一个球，然后上下或左右。添加的任何其他球都必须向上或向下移动？任何帮助都会很棒。谢谢。

import javafx.animation.KeyFrame;
import javafx.animation.Timeline;
import javafx.application.Application;
import javafx.beans.property.DoubleProperty;
import javafx.geometry.Pos;
import javafx.scene.Node;
import javafx.stage.Stage;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.ScrollBar;
import javafx.scene.layout.BorderPane;
import javafx.scene.layout.HBox;
import javafx.scene.layout.Pane;
import javafx.scene.paint.Color;
import javafx.scene.shape.Circle;
import javafx.util.Duration;

public class MultipleBounceBall extends Application {
  @Override // Override the start method in the Application class
  public void start(Stage primaryStage) {
    MultipleBallPane ballPane = new MultipleBallPane();
    ballPane.setStyle("-fx-border-color: black");

    Button btAdd = new Button("+");
    Button btSubtract = new Button("-");
    HBox hBox = new HBox(10);
    hBox.getChildren().addAll(btAdd, btSubtract);
    hBox.setAlignment(Pos.CENTER);

    // Add or remove a ball
    btAdd.setOnAction(e -> ballPane.add());
    btSubtract.setOnAction(e -> ballPane.subtract());

    // Pause and resume animation
    ballPane.setOnMousePressed(e -> ballPane.pause());
    ballPane.setOnMouseReleased(e -> ballPane.play());

    // Use a scroll bar to control animation speed
    ScrollBar sbSpeed = new ScrollBar();
    sbSpeed.setMax(20);
    sbSpeed.setValue(10);
    ballPane.rateProperty().bind(sbSpeed.valueProperty());

    BorderPane pane = new BorderPane();
    pane.setCenter(ballPane);
    pane.setTop(sbSpeed);
    pane.setBottom(hBox);

    // Create a scene and place the pane in the stage
    Scene scene = new Scene(pane, 350, 450);
    primaryStage.setTitle("Multiple Bounce Ball"); // Set the stage title
    primaryStage.setScene(scene); // Place the scene in the stage
    primaryStage.show(); // Display the stage
  }

  private class MultipleBallPane extends Pane {
    private Timeline animation;

    public MultipleBallPane() {
      // Create an animation for moving the ball
      animation = new Timeline(
        new KeyFrame(Duration.millis(50), e -> moveBall()));
      animation.setCycleCount(Timeline.INDEFINITE);
      animation.play(); // Start animation
    }

    public void add() {
      Color color = new Color(Math.random(), 
        Math.random(), Math.random(), 0.5);
      getChildren().add(new Ball(30, 30, 20, color)); 
    }

    public void subtract() {
      if (getChildren().size() > 0) {
        getChildren().remove(getChildren().size() - 1); 
      }
    }

    public void play() {
      animation.play();
    }

    public void pause() {
      animation.pause();
    }

    public void increaseSpeed() {
      animation.setRate(animation.getRate() + 0.1);
    }

    public void decreaseSpeed() {
      animation.setRate(
        animation.getRate() > 0 ? animation.getRate() - 0.1 : 0);
    }

    public DoubleProperty rateProperty() {
      return animation.rateProperty();
    }

    protected void moveBall() {
      for (Node node: this.getChildren()) {
        Ball ball = (Ball)node;
        // Check boundaries
        if (ball.getCenterX() < ball.getRadius() || 
            ball.getCenterX() > getWidth() - ball.getRadius()) {
          ball.dx *= -1; // Change ball move direction
        }
        if (ball.getCenterY() < ball.getRadius() || 
            ball.getCenterY() > getHeight() - ball.getRadius()) {
          ball.dy *= -1; // Change ball move direction
        }

        // Adjust ball position
        ball.setCenterX(ball.dx + ball.getCenterX());
        ball.setCenterY(ball.dy + ball.getCenterY());
      }
    }
  }

  class Ball extends Circle {
    private double dx = 1, dy = 1;

    Ball(double x, double y, double radius, Color color) {
      super(x, y, radius);
      setFill(color); // Set ball color
    }
  }

  /**
   * The main method is only needed for the IDE with limited
   * JavaFX support. Not needed for running from the command line.
   */
  public static void main(String[] args) {
    launch(args);
  }
}

Answer 1

问题在于球运动的位移元素（dx和dy）都被指定为1.因此球向x和y方向移动，即对角线移动。将这些变量的声明更改为：

private double dx = 1, dy = 0; // The ball will move right
private double dx = -1, dy = 0; // The ball will move left
private double dx = 0, dy = 1; // The ball will move down
private double dx = 0, dy = -1; // The ball will move up

如果您希望球在随机方向上移动，您可以通过更改Ball课程来实现：

class Ball extends Circle {
    private double dx;
    private double dy;

    Ball(double x, double y, double radius, Color color) {
        super(x, y, radius);
        setFill(color); // Set ball color
        switch (ThreadLocalRandom.current().nextInt(0, 4)) {
            case 0:
                dx = 0;
                dy = 1;
                break;
            case 1:
                dx = 0;
                dy = -1;
                break;
            case 2:
                dx = 1;
                dy = 0;
                break;
            case 3:
                dx = -1;
                dy = 0;
                break;
        }
    }
}

如果您希望他们从随机位置开始，您可以通过更改MultipleBallPane.add()方法来完成此操作：

public void add() {
    Color color = new Color(Math.random(),
            Math.random(), Math.random(), 0.5);
    int radius = 20;
    int x = ThreadLocalRandom.current().nextInt(radius, (int) getWidth() - radius);
    int y = ThreadLocalRandom.current().nextInt(radius, (int) getHeight() - radius);
    getChildren().add(new Ball(x, y, radius, color));
}

如何在JavaFX中使球向上或向下移动？

1 个答案: