JavaFX中如何让球从墙上弹开？
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How to make the ball bounce off the walls in JavaFX?
提问by Gregg1989
I am new to Javafx and I am creating a simple program. What I'm trying to achieve is get the ball to bounce off the walls, but I haven't figured out how to do that yet. Also, feel free to leave other suggestions about my code.
我是 Javafx 的新手，我正在创建一个简单的程序。我想要实现的是让球从墙上弹开，但我还没有想出如何做到这一点。另外，请随意留下关于我的代码的其他建议。
Here's the source code:
这是源代码：
public class GamePractice extends Application {
public static Circle circle;
public static Pane canvas;
private long counter = 0;
@Override
public void start(Stage primaryStage) {
canvas = new Pane();
Scene scene = new Scene(canvas, 800, 600);
primaryStage.setTitle("Game");
primaryStage.setScene(scene);
primaryStage.show();
circle = new Circle(15,Color.BLUE);
circle.relocate(100, 100);
canvas.getChildren().addAll(circle);
Timeline loop = new Timeline(new KeyFrame(Duration.millis(10), new EventHandler<ActionEvent>() {
@Override
public void handle(ActionEvent t) {
if (counter++ % 10 == 0)
{
circle.setLayoutX(circle.getLayoutX() + 10);
circle.setLayoutY(circle.getLayoutY() + 10);
//This is what I currently have, am I headed the right direction?
//Check X and Y for collision with the ball
if ((circle.getTranslateX() == canvas.getWidth() - 10) || (circle.getTranslateY() == canvas.getHeight() - 10)) {
//How do I make the ball bounce?
}
}
}
}));
loop.setCycleCount(Timeline.INDEFINITE);
loop.play();
}
I appreciate the help.
我很感激你的帮助。
采纳答案by Jens Piegsa
One hint: you should avoid comparing double values for exact equalitya == b.
一个提示：您应该避免比较 double 值以获得精确相等a == b。
With some small changes of your code you're already there:
对您的代码进行一些小的更改，您已经在那里了：
package learn.javafx;
import javafx.animation.KeyFrame;
import javafx.animation.Timeline;
import javafx.application.Application;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.geometry.Bounds;
import javafx.scene.Scene;
import javafx.scene.layout.Pane;
import javafx.scene.paint.Color;
import javafx.scene.shape.Circle;
import javafx.stage.Stage;
import javafx.util.Duration;
public class GamePractice extends Application {
public static Circle circle;
public static Pane canvas;
@Override
public void start(final Stage primaryStage) {
canvas = new Pane();
final Scene scene = new Scene(canvas, 800, 600);
primaryStage.setTitle("Game");
primaryStage.setScene(scene);
primaryStage.show();
circle = new Circle(15, Color.BLUE);
circle.relocate(100, 100);
canvas.getChildren().addAll(circle);
final Timeline loop = new Timeline(new KeyFrame(Duration.millis(10), new EventHandler<ActionEvent>() {
double deltaX = 3;
double deltaY = 3;
@Override
public void handle(final ActionEvent t) {
circle.setLayoutX(circle.getLayoutX() + deltaX);
circle.setLayoutY(circle.getLayoutY() + deltaY);
final Bounds bounds = canvas.getBoundsInLocal();
final boolean atRightBorder = circle.getLayoutX() >= (bounds.getMaxX() - circle.getRadius());
final boolean atLeftBorder = circle.getLayoutX() <= (bounds.getMinX() + circle.getRadius());
final boolean atBottomBorder = circle.getLayoutY() >= (bounds.getMaxY() - circle.getRadius());
final boolean atTopBorder = circle.getLayoutY() <= (bounds.getMinY() + circle.getRadius());
if (atRightBorder || atLeftBorder) {
deltaX *= -1;
}
if (atBottomBorder || atTopBorder) {
deltaY *= -1;
}
}
}));
loop.setCycleCount(Timeline.INDEFINITE);
loop.play();
}
public static void main(final String[] args) {
launch(args);
}
}
