单击创建按钮时，java fx创建球

Question

I am trying to create balls whenever create button is clicked. I am able to create a single ball but for some reason not able to create multiple balls when the 'Create' button is clicked repeatedly.

Any help is appreciated.

package week3;

import javafx.application.Application;
import javafx.stage.Stage;
import javafx.scene.Scene;
import javafx.scene.control.Slider;
import javafx.scene.control.Button;
import javafx.scene.layout.BorderPane;
import javafx.scene.layout.TilePane;
import javafx.geometry.Orientation;
import javafx.geometry.Insets;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.animation.KeyFrame;
import javafx.animation.Timeline;
import javafx.beans.property.DoubleProperty;
import javafx.scene.layout.Pane;
import javafx.scene.paint.Color;
import javafx.scene.shape.Circle;
import javafx.util.Duration;



public class BounceBallControl1 extends Application {
        public final double radius = 10;
        private double x = radius, y = radius;
        private double dx = 1, dy = 1;
        private Circle circle = new Circle(x, y, radius);
        private Timeline animation;
@SuppressWarnings("restriction")
@Override // Override the start method in the Application class
public void start(Stage primaryStage) {
//BallPane ballPane = new BallPane();

Button btnCreate = new Button("Create");
Button btnDelete = new Button("Delete");
btnCreate.setMaxSize(Double.MAX_VALUE, Double.MAX_VALUE);
btnDelete.setMaxSize(Double.MAX_VALUE, Double.MAX_VALUE);
TilePane tileButtons = new TilePane(Orientation.HORIZONTAL);
tileButtons.setPadding(new Insets(5, 5, 5, 70));
tileButtons.setHgap(20.0);
tileButtons.getChildren().addAll(btnCreate, btnDelete);

Slider slSpeed = new Slider();
slSpeed.setMax(20);
//rateProperty().bind(slSpeed.valueProperty());

BorderPane pane = new BorderPane();
//pane.setCenter(ballPane);
pane.setTop(slSpeed);
pane.setBottom(tileButtons);

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

    public void handle(ActionEvent event) {
        for(int i=0;i<=100;i++)
        circle.setFill(Color.TURQUOISE); // Set ball color
        pane.getChildren().add(circle); // Place a ball into this pane

        // Create an animation for moving the ball
        animation = new Timeline(
        new KeyFrame(Duration.millis(50), (e -> {
            // Check boundaries
            if (x < radius || x > pane.getWidth() - radius) {
            dx *= -1; // Change ball move direction
            }
            if (y < radius || y > pane.getHeight() - radius) {
            dy *= -1; // Change ball move direction
            }

            // Adjust ball position
            x += dx;
            y += dy;
            circle.setCenterX(x);
            circle.setCenterY(y);
            })));
        animation.setCycleCount(Timeline.INDEFINITE);
        animation.play(); // Start animation
    }
});



// Create a scene and place it in the stage
Scene scene = new Scene(pane, 250, 250);
primaryStage.setTitle("BounceBallSlider"); // Set the stage title
primaryStage.setScene(scene); // Place the scene in the stage
primaryStage.show(); // Display the stage
}

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

Answer 1

You use the same instance of circle each time you click add button. So every time the same circle is added to the scene. Try by creating new circle each time, it will be ok.