编辑：更新的代码和问题
我添加了 main（） 方法，如 aswers 中所述，但我仍然无法导出它。我正在以 Java Applet 的身份运行我的程序，显然我需要使用 Java 应用程序独立运行它，但是当我将运行配置更改为应用程序时，我收到以下错误：
Exception in thread "main" java.lang.NullPointerException
at acm.graphics.GImage.determineSize(GImage.java:564)
at acm.graphics.GImage.setImage(GImage.java:173)
at acm.graphics.GImage.<init>(GImage.java:115)
at acm.graphics.GImage.<init>(GImage.java:54)
at Pong.createTexture(Pong.java:160)
at Pong.run(Pong.java:81)
at Pong.main(Pong.java:55)
我需要将我的项目从 Eclipse 导出为独立的可运行 JAR，但是当我导出 -> java -> JAR 文件时，我没有看到任何可供选择的类，并且我卡在这个（屏幕）窗口中。我的项目中只有一个类。
这不再相关，但我会把它留在这里以保留编辑历史记录
import java.awt.Color;
import java.awt.Image;
import java.awt.event.MouseEvent;
import java.util.Random;
import acm.graphics.GImage;
import acm.graphics.GLabel;
import acm.graphics.GObject;
import acm.graphics.GOval;
import acm.graphics.GRect;
import acm.program.GraphicsProgram;
/* TO DO LIST
* ------------------
* Corner Bounce
*
*
*
*/
@SuppressWarnings("serial")
public class Pong extends GraphicsProgram {
public double mouseY;
private static final double PAUSE = 1000 / 96.0;
private Random rand = new Random();
private boolean AI_GODMODE = false;
// ball
public double startX;
public double startY;
private static final double BALL_SIZE = 20;
private static final double SPEED = 5;
private double ballHorizontalSpeed = SPEED * 1.5;
private double ballVerticalSpeed = SPEED;
// paddle
private static int HEIGHT = 150;
private static int WIDTH = 15;
private static int COUNTER = 0;
private static int AI_SPEED = 10; // AI difficulty 1-20
// label
public int AI_SCORE = 0;
public int PLAYER_SCORE = 0;
public int TOTAL_GAMES = 0;
private float TRANSPARENCY = 0.0f;
// counters
private static final int PADDING = 10;
private static final int MODIFIER = 3;
public static void main(String[] args) {
Pong p = new Pong();
p.run();
}
public void run() {
addMouseListeners();
// counters setup
GLabel counter = new GLabel(String.valueOf(COUNTER));
GLabel aiScore = new GLabel(String.valueOf(AI_SCORE));
GLabel average = new GLabel(String.valueOf("Avg: 0"));
GLabel playerScore = new GLabel(String.valueOf(COUNTER));
Color labelC = new Color(0, 0.0f, 0.0f, TRANSPARENCY);
Color scoreC = new Color(0, 0.0f, 0.0f, 0.1f);
counter.setFont("Impact-600");
aiScore.setFont("Impact-100");
average.setFont("Impact-50");
playerScore.setFont("Impact-100");
counter.setColor(labelC);
aiScore.setColor(scoreC);
playerScore.setColor(scoreC);
average.setColor(scoreC);
counter.setLocation(getWidth() / 2 - counter.getWidth() / 2,
getHeight() / 2 + counter.getHeight() / 3.2);
counter.sendToFront();
// make objects
GImage paddleLeftTexture = createTexture("texture.png", WIDTH + 1,
HEIGHT + 1);
GImage paddleRightTexture = createTexture("texture2.png", WIDTH + 1,
HEIGHT + 1);
GImage ballTexture = createTexture("ballTexture.png", (int) BALL_SIZE,
(int) BALL_SIZE);
GImage greenFlash = createTexture("greenFlash.png", 100, 300);
GImage blueFlash = createTexture("blueFlash.png", 100, 300);
GOval ball = makeBall();
GRect paddleLeft = makePaddle();
GRect paddleRight = makePaddle();
greenFlash.setLocation(-200, 0);
blueFlash.setLocation(-200, 0);
// generate GUI
drawGraphics(ball, paddleLeftTexture, paddleRightTexture, ballTexture,
greenFlash, blueFlash, counter, paddleLeft, paddleRight,
aiScore, playerScore, average);
// game start
bounce(labelC, aiScore, playerScore, counter, ball, paddleLeft,
paddleRight, paddleLeftTexture, paddleRightTexture,
ballTexture, greenFlash, blueFlash, average);
}
public void bounce(Color labelC, GLabel aiScore, GLabel playerScore,
GLabel counter, GOval ball, GRect paddleLeft, GRect paddleRight,
GImage paddleLeftTexture, GImage paddleRightTexture,
GImage ballTexture, GImage greenFlash, GImage blueFlash,
GLabel average) {
preGameSetup(ball, paddleRight, paddleRightTexture, counter);
updateAiScore(aiScore);
updatePlayerScore(playerScore);
updateAverage(average);
while (true) {
moveBall(ballHorizontalSpeed, ballVerticalSpeed, ball, ballTexture);
movePlayerPaddle(paddleLeft, paddleLeftTexture);
moveAiPaddle(ball, paddleRight, paddleRightTexture);
detectHit(ball, paddleRight, paddleLeft, counter, labelC);
if (TRANSPARENCY >= 0.0f) {
TRANSPARENCY -= TRANSPARENCY / 100f;
}
labelC = new Color(0, 0.0f, 0.0f, TRANSPARENCY);
counter.setColor(labelC);
if (detectBallOffScreen(ball)) {
ballOffScreen(ball, ballTexture, aiScore, playerScore,
greenFlash, blueFlash, average);
COUNTER = 0;
bounce(labelC, aiScore, playerScore, counter, ball, paddleLeft,
paddleRight, paddleLeftTexture, paddleRightTexture,
ballTexture, greenFlash, blueFlash, average);
}
pause(PAUSE);
}
}
public static GRect makePaddle() {
GRect result = new GRect(0, 0, WIDTH, HEIGHT);
result.setFilled(true);
result.setColor(Color.BLACK);
return result;
}
public static GOval makeBall() {
GOval result = new GOval(150, 100, BALL_SIZE, BALL_SIZE);
result.setFilled(true);
result.setColor(Color.WHITE);
return result;
}
private GImage createTexture(String importedImage, int width, int height) {
Image importResult = getImage(getCodeBase(), importedImage);
GImage textureResult = new GImage(importResult);
textureResult.setSize(width, height);
return textureResult;
}
public void mouseMoved(MouseEvent e) {
mouseY = e.getY();
}
private boolean ballHitBottom(GOval ball) {
double bottomY = ball.getY() + ball.getHeight();
return bottomY >= getHeight();
}
private boolean ballHitTop(GOval ball) {
double topY = ball.getY();
return topY <= 0;
}
private boolean ballHitPaddleRight(GOval ball, GRect paddle) {
double rightX = ball.getX() + ball.getWidth();
double rightY = ball.getY() + ball.getHeight() / 2;
double paddlePosX = paddle.getX();
double paddlePosY = paddle.getY();
if (rightX >= paddlePosX && rightY >= paddlePosY
&& rightY <= paddlePosY + paddle.getHeight())
return true;
else
return false;
}
private boolean detectBallOffScreen(GOval ball) {
if (ball.getX() < 2 * WIDTH - BALL_SIZE
|| ball.getX() > getWidth() - 2 * WIDTH)
return true;
else
return false;
}
private boolean ballHitPaddleLeft(GOval ball, GRect paddle) {
double leftX = ball.getX();
double leftY = ball.getY();
double paddlePosX = paddle.getX() + WIDTH;
double paddlePosY = paddle.getY();
if (leftX <= paddlePosX && leftY >= paddlePosY
&& leftY <= paddlePosY + paddle.getHeight())
return true;
else
return false;
}
/*
* private boolean ballHitPaddleBorder(GOval ball, GRect paddle) { ; if
* (ball.getX() > paddle.getX() - BALL_SIZE && ball.getX() < paddle.getX() +
* WIDTH && ball.getY() > paddle.getY() && ball.getY() < paddle.getY() +
* ballVerticalSpeed) return true; else if (ball.getX() > paddle.getX() -
* BALL_SIZE && ball.getX() < paddle.getX() + WIDTH && ball.getY() >
* paddle.getY() + HEIGHT && ball.getY() < paddle.getY() + HEIGHT -
* ballVerticalSpeed) return true; else return false; }
*/
private void preGameSetup(GObject ball, GObject paddleRight,
GObject paddleRightTexture, GLabel counter) {
startX = rand.nextInt((int) (getWidth() * 0.8))
+ (int) (0.1 * getWidth()); // zapobiega pojawieniu się piłki po
// lewej stronie lewej paletki
startY = rand.nextInt(getHeight());
ball.setLocation(startX, startY);
paddleRightTexture.setLocation(getWidth() - MODIFIER * WIDTH, startY
- HEIGHT / 2);
paddleRight.setLocation(getWidth() - MODIFIER * WIDTH, startY - HEIGHT
/ 2);
paddleRightTexture.sendToFront();
counter.setLabel(String.valueOf(COUNTER));
counter.setLocation(getWidth() / 2 - counter.getWidth() / 2,
getHeight() / 2 + counter.getHeight() / 3.2);
ballHorizontalSpeed = SPEED * 1.5;
ballVerticalSpeed = SPEED;
}
private void updateAiScore(GLabel aiScore) {
aiScore.setLabel(String.valueOf(AI_SCORE));
aiScore.setLocation(getWidth() - aiScore.getWidth() - MODIFIER * WIDTH
- PADDING, getHeight() - PADDING);
}
private void updatePlayerScore(GLabel playerScore) {
playerScore.setLabel(String.valueOf(PLAYER_SCORE));
playerScore.setLocation(MODIFIER * WIDTH + PADDING, getHeight()
- PADDING);
}
private void updateScore(GLabel counter, Color labelC) {
counter.setLabel(String.valueOf(COUNTER));
counter.setLocation(getWidth() / 2 - counter.getWidth() / 2,
getHeight() / 2 + counter.getHeight() / 3.2);
TRANSPARENCY = 0.1f;
labelC = new Color(0, 0.0f, 0.0f, TRANSPARENCY);
counter.setColor(labelC);
}
private void updateAverage(GLabel average) {
if (TOTAL_GAMES == 0) {
average.setLabel("Round: 1 Avg: 0");
} else {
average.setLabel("Round: " + String.valueOf(TOTAL_GAMES + 1) + " Avg: "
+ String.valueOf((int) ((AI_SCORE + PLAYER_SCORE) / TOTAL_GAMES)));}
average.setLocation(getWidth() / 2 - average.getWidth() / 2,
getHeight() - PADDING);
}
private void drawGraphics(GObject ball, GObject paddleLeftTexture,
GObject paddleRightTexture, GObject ballTexture,
GObject greenFlash, GObject blueFlash, GObject counter,
GObject paddleLeft, GObject paddleRight, GObject aiScore,
GObject playerScore, GLabel average) {
add(ball);
add(paddleLeftTexture);
add(paddleRightTexture);
add(ballTexture);
add(greenFlash);
add(blueFlash);
add(counter);
add(paddleLeft);
add(paddleRight);
add(aiScore);
add(playerScore);
add(average);
}
private void detectHit(GOval ball, GRect paddleRight, GRect paddleLeft,
GLabel counter, Color labelC) {
if (ballHitBottom(ball) && ballVerticalSpeed >= 0) {
ballVerticalSpeed *= -1;
}
if (ballHitTop(ball) && ballVerticalSpeed <= 0) {
ballVerticalSpeed *= -1;
}
if (ballHitPaddleRight(ball, paddleRight)) {
ballHorizontalSpeed *= -1;
}
if (ballHitPaddleLeft(ball, paddleLeft)) {
ballHorizontalSpeed *= -1;
COUNTER++;
updateScore(counter, labelC);
boolean bool = rand.nextBoolean();
if (bool)
if (ballHorizontalSpeed > 0)
ballHorizontalSpeed += 1;
else
ballHorizontalSpeed -= 1;
else if (ballVerticalSpeed > 0)
ballVerticalSpeed += 0.5;
else
ballVerticalSpeed -= 0.5;
}
/*
* if(ballHitPaddleBorder(ball, paddleLeft)){ ballVerticalSpeed *= -1; }
*
* if(ballHitPaddleBorder(ball, paddleRight)){ ballVerticalSpeed *= -1;
* }
*/
}
private void ballOffScreen(GOval ball, GObject ballTexture, GLabel aiScore,
GLabel playerScore, GObject greenFlash, GObject blueFlash,
GLabel average) {
if (ball.getX() < 2 * WIDTH - BALL_SIZE) { // left
double pos = ball.getY() - greenFlash.getHeight() / 2;
ballTexture.move(-ballTexture.getWidth() * 2, 0);
AI_SCORE += COUNTER;
TOTAL_GAMES++;
updateAiScore(aiScore);
updateAverage(average);
for (int i = 20; i < 100; i += 5) {
greenFlash.setLocation(-i, pos);
pause(25);
}
} else { // right
double pos = ball.getY() - blueFlash.getHeight() / 2;
ballTexture.move(ballTexture.getWidth() * 2, 0);
PLAYER_SCORE += COUNTER;
TOTAL_GAMES++;
updatePlayerScore(playerScore);
updateAverage(average);
for (int i = 20; i < 100; i += 5) {
blueFlash.setLocation(getWidth() - blueFlash.getWidth() + i,
pos);
pause(25);
}
}
}
private void moveBall(double ballHorizontalSpeed, double ballVerticalSpeed,
GObject ball, GObject ballTexture) {
ball.move(ballHorizontalSpeed, ballVerticalSpeed);
ballTexture.setLocation(ball.getX(), ball.getY());
ballTexture.sendToFront();
}
private void movePlayerPaddle(GObject paddleLeft, GObject paddleLeftTexture) {
if (mouseY < getHeight() - HEIGHT) { // Player
paddleLeft.setLocation(2 * WIDTH, mouseY);
paddleLeftTexture.setLocation(2 * WIDTH, mouseY);
paddleLeftTexture.sendToFront();
} else {
paddleLeft.setLocation(2 * WIDTH, getHeight() - HEIGHT);
paddleLeftTexture.setLocation(2 * WIDTH, getHeight() - HEIGHT);
paddleLeftTexture.sendToFront();
}
}
private void moveAiPaddle(GOval ball, GRect paddleRight,
GImage paddleRightTexture) {
if (AI_GODMODE == true) { // modeSelector
if (ball.getY() < getHeight() - HEIGHT / 2
&& ball.getY() > HEIGHT / 2) {
paddleRight.setLocation(getWidth() - MODIFIER * WIDTH,
ball.getY() - HEIGHT / 2);
paddleRightTexture.setLocation(getWidth() - MODIFIER * WIDTH,
ball.getY() - HEIGHT / 2);
paddleRightTexture.sendToFront();
} else if (ball.getY() <= HEIGHT / 2) {
paddleRight.setLocation(getWidth() - MODIFIER * WIDTH, 0);
paddleRightTexture.setLocation(getWidth() - MODIFIER * WIDTH,
-0);
paddleRightTexture.sendToFront();
} else {
paddleRight.setLocation(getWidth() - MODIFIER * WIDTH,
getHeight() - HEIGHT);
paddleRightTexture.setLocation(getWidth() - MODIFIER * WIDTH,
getHeight() - HEIGHT);
paddleRightTexture.sendToFront();
}
} else { // end godMode if
double targetY = ball.getY() + BALL_SIZE / 2;
if (targetY < getHeight() - HEIGHT / 2 && targetY > HEIGHT / 2) {
if (targetY < paddleRight.getY() + HEIGHT / 2) {
paddleRight.move(0, -AI_SPEED);
paddleRightTexture.move(0, -AI_SPEED);
} else if (targetY > paddleRight.getY() + HEIGHT / 2) {
paddleRight.move(0, AI_SPEED);
paddleRightTexture.move(0, AI_SPEED);
}
} // end normalMode if
} // end modeSelector if
} // end moveAiPaddle void
} // end class
从链接的图像来看，您的类 Pong 没有主方法。它根本无法导出为可运行的 jar 文件，因为您永远无法运行它。添加一个 main 方法，或导出到标准 java jar 文件（文件 -> Export -> Java -> JAR 文件）。如果没有主方法，句号，它使用后一种方法生成的 jar 文件将无法运行。您必须有一个 main 方法才能独立运行此代码，因为这是应用程序的入口点。
根据您的评论，您需要在 main 方法内创建一个 Pong 类的实例并调用其 run（） 方法：
public static void main(String[] args) {
Pong p = new Pong();
p.run();
}
如果 Pong 类的 run 方法是静态的，则不需要实例，您可以这样做：
public static void main(String[] args) {
Pong.run();
}
您应该将其导出为"可运行的JAR文件"而不是"JAR文件"。选择此选项后，您应该能够使用名为"启动配置："的下拉菜单，然后您可以选择导出目的地。
我正在使用Eclipse Kepler。对于不同的版本，它可能不一样。
您的项目应包含带有 main 方法的类，以便您可以在"启动配置"下拉列表中看到您的项目。（日食开普勒）