我正在尝试创建一个类似Pong的游戏，我已经开始实现一些关于桨的运动的代码。关于桨叶本身的运动，一切都很好。然而，当我突然改变桨叶的方向时会出现问题（更具体地说，当我立即从桨叶向上移动到向下切换时，反之亦然）。桨在原地冻结几秒钟，然后沿所需的方向前进。
我已经尝试过当我移除canvas.setOnKeyReleased(new KeyReleasedHandler());时会发生什么，但是然后拨片在不停止的情况下向同一方向移动。我想在释放钥匙后能够停止桨的运动。
以下是MainApplication：
public class Pong2App extends Application {
private static final double CANVAS_WIDTH = 900;
private static final double CANVAS_HEIGHT = 500;
private static final double ELAPSED_TIME_SPEED = 1.85;
Ball testBall;
Paddle leftPaddle;
@Override
public void start(Stage primaryStage) throws Exception {
Group root = new Group();
Scene scene = new Scene(root);
primaryStage.setScene(scene);
Canvas canvas = new Canvas(CANVAS_WIDTH, CANVAS_HEIGHT);
Bounds canvasBounds = canvas.getBoundsInLocal();
root.getChildren().add(canvas);
GraphicsContext gc = canvas.getGraphicsContext2D();
// TODO: remove testBall and leftPaddle; Gives testBall random vX and vY
testBall = new Ball(CANVAS_WIDTH / 2, CANVAS_HEIGHT / 2.5, 30, 30, gc);
Random tempRand = new Random();
testBall.setvX((tempRand.nextDouble() * 4) * (tempRand.nextBoolean() ? -1 : 1));
testBall.setvY((tempRand.nextDouble() * 4) * (tempRand.nextBoolean() ? -1 : 1));
leftPaddle = new Paddle(70, CANVAS_HEIGHT / 2.5, 10, 100, "Left", gc);
canvas.setFocusTraversable(true);
canvas.setOnKeyPressed(new KeyPressedHandler());
canvas.setOnKeyReleased(new KeyReleasedHandler());
new AnimationTimer() {
@Override
public void handle(long currentTime) {
testBall.didCollideWithWalls(canvas);
if (leftPaddle.getY() <= canvasBounds.getMinY() + 5)
leftPaddle.setY(canvasBounds.getMinY() + 5);
if (leftPaddle.getY() >= canvasBounds.getMaxY() - 105)
leftPaddle.setY(canvasBounds.getMaxY() - 105);
if (leftPaddle.didCollideWith(testBall)) {
testBall.setvX(-testBall.getvX());
testBall.setX(testBall.getX() + testBall.getvX());
}
testBall.update(ELAPSED_TIME_SPEED);
leftPaddle.update(ELAPSED_TIME_SPEED);
gc.clearRect(0, 0, CANVAS_WIDTH, CANVAS_HEIGHT);
testBall.render(gc);
leftPaddle.render(gc);
}
}.start();
primaryStage.show();
}
public static void main(String[] args) {
launch(args);
}
/**
* Handles what happens when a key is pressed. Depending on what key is pressed,
* the paddle will move up or down.
*
* @author Phillip
*
*/
private class KeyPressedHandler implements EventHandler<KeyEvent> {
@Override
public void handle(KeyEvent event) {
switch (event.getCode()) {
case W:
leftPaddle.moveUp();
break;
case S:
leftPaddle.moveDown();
break;
default:
break;
}
}
}
/**
* Handles what happens when a key is released. Depending on what key is
* released, the paddle will stop moving.
*
* @author Phillip
*
*/
private class KeyReleasedHandler implements EventHandler<KeyEvent> {
@Override
public void handle(KeyEvent event) {
switch (event.getCode()) {
case W:
case S:
leftPaddle.setvY(0);
break;
default:
break;
}
}
}
}
这是Paddle Class：
public class Paddle extends Sprite {
private int points;
private String name;
private static final double PADDLE_SPEED = 2.5;
public Paddle(double x, double y, double width, double height, String name, GraphicsContext gc) {
super(x, y, width, height, gc);
this.points = 0;
this.name = name;
}
@Override
public boolean didCollideWith(Sprite other) {
Ball ball = (Ball) other;
double ballCenterX = ball.getCenterX();
double ballRadius = ball.getRadius();
double ballCenterY = ball.getCenterY();
double halfWidth = this.getHalfWidth();
double halfHeight = this.getHalfHeight();
double centerX = this.getCenterX();
double centerY = this.getCenterY();
if (getName().equals("Left")) {
boolean hitXBounds = ballCenterX - ballRadius <= centerX + halfWidth;
boolean hitTopPartOfBall = ballCenterY - ballRadius <= centerY + halfHeight
&& ballCenterY - ballRadius >= centerY - halfHeight;
boolean hitBotPartOfBall = ballCenterY + ballRadius <= centerY + halfHeight
&& ballCenterY + ballRadius >= centerY - halfHeight;
return hitXBounds && (hitTopPartOfBall || hitBotPartOfBall);
}
return false;
}
@Override
public void render(GraphicsContext gc) {
gc.fillRect(getX(), getY(), getWidth(), getHeight());
}
@Override
public boolean didCollideWithWalls(Canvas canvas) {
Bounds bounds = canvas.getBoundsInLocal();
boolean atTopWall = this.getY() <= bounds.getMinY();
boolean atBotWall = this.getY() >= bounds.getMaxY();
if (atTopWall || atBotWall) {
return true;
}
return false;
}
public int getPoints() {
return points;
}
public void setPoints(int points) {
this.points = points;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public void moveUp() {
this.setvY(-PADDLE_SPEED);
}
public void moveDown() {
this.setvY(PADDLE_SPEED);
}
}
谢谢！
答案 0 :(得分：2)
如果按，例如W，然后按S，然后按顺序发布W，
setvY(-PADDLE_SPEED)，setvY(PADDLE_SPEED)，setvY(0)，这可能不是您打算做的：即使vY=0仍被按下，它也会产生S。
在此之后的某个时刻，本机键盘重复将在S上再次按下，因此您再次呼叫setvY(PADDLE_SPEED)，并且拨片开始移动。考虑使用两个布尔值（moveUp和moveDown）并将其设置为true和false，然后根据其值更新速度。 E.g。
public class Paddle extends Sprite {
private boolean moveUp ;
private boolean moveDown ;
// ...
public void setMoveUp(boolean moveUp) {
this.moveUp = moveUp ;
updateVy();
}
public void setMoveDown(booleam moveDown) {
this.moveDown = moveDown ;
updateVy();
}
private void updateVy() {
setvY(
(moveUp ? -PADDLE_SPEED : 0) +
(moveDown ? PADDLE_SPEED : 0)
);
}
// ...
}
然后在你的处理程序中
private class KeyPressedHandler implements EventHandler<KeyEvent> {
@Override
public void handle(KeyEvent event) {
switch (event.getCode()) {
case W:
leftPaddle.setMoveUp(true);
break;
case S:
leftPaddle.setMoveDown(true);
break;
default:
break;
}
}
}
和
private class KeyReleasedHandler implements EventHandler<KeyEvent> {
@Override
public void handle(KeyEvent event) {
switch (event.getCode()) {
case W:
leftPaddle.setMoveUp(false);
break ;
case S:
leftPaddle.setMoveDown(false);
break;
default:
break;
}
}
}