对象和计时器（For 循环）
Objects and Timers (For Loops)
这是一个学校项目。我正在尝试进行碰撞游戏，目标是躲避球。我目前正在努力尝试每 30 秒左右添加一个球，但遇到了问题。我已经尝试了 for 循环和计时器来解决这部分（在我有 for 循环的代码中）。我反复得到相同的结果：球仍然在那里但看不见。如果有人知道如何解决此问题或可能有效的其他方法，请提供帮助。谢谢！
import java.awt.*;
import java.lang.*;
import java.awt.event.KeyEvent;
import java.util.Formatter;
import javax.swing.*;
import java.awt.event.*;
import java.awt.Polygon;
import java.awt.geom.Area;
public class Man extends JComponent implements KeyListener {
private static final int BOX_WIDTH = 640;
private static final int BOX_HEIGHT = 480;
private float ballSpeedX3 = 7;
private float ballSpeedY3 = 7;
private double ball3Radius = 20;
private double ball3X = 320 ;
private double ball3Y = 120 ;
private float ballSpeedX4 = -10;
private float ballSpeedY4 = 10;
private double ball4Radius = 15;
private double ball4X = 600 ;
private double ball4Y = 300 ;
private float ballSpeedX = 0;
private float ballSpeedY = 0;
private double ballRadius = 20;
private double ballX = 120;
private double ballY = 140;
private float ballSpeed1X = 10;
private float ballSpeed1Y = -10;
private double ballRadius1 = 20;
private double ball1X = 320;
private double ball1Y = 340;
private float ballSpeed2X = -3;
private float ballSpeed2Y = -3;
private double ballRadius2 = 50;
private double ball2X = 50;
private double ball2Y = 400;
private static final int UPDATE_RATE = 30;
public Man() {
this.setPreferredSize(new Dimension(BOX_WIDTH, BOX_HEIGHT));
Thread gameThread = new Thread() {
public void run() {
while(true){
if ( Math.sqrt( (Math.pow((ballX- ball1X), 2)) + Math.pow((ballY-ball1Y), 2)) <= (ballRadius1 + ballRadius)) {
System.exit(0);}
if ( Math.sqrt( (Math.pow((ball4X- ballX), 2)) + Math.pow((ball4Y-ballY), 2)) <= (ball4Radius + ballRadius)) {
System.exit(0);}
if ( Math.sqrt( (Math.pow((ball2X- ballX), 2)) + Math.pow((ball2Y-ballY), 2)) <= (ballRadius2 + ballRadius)) {
System.exit(0);}
ball4X += ballSpeedX4;
ball4Y += ballSpeedY4;
if (ball4X - ball4Radius < 0) {
ballSpeedX4 = -ballSpeedX4;
ball4X = ball4Radius;
} else if (ball4X + ball4Radius > BOX_WIDTH) {
ballSpeedX4 = -ballSpeedX4;
ball4X = BOX_WIDTH - ball4Radius;
}
if (ball4Y - ball4Radius < 0) {
ballSpeedY4 = -ballSpeedY4;
ball4Y = ball4Radius;
} else if (ball4Y + ball4Radius > BOX_HEIGHT) {
ballSpeedY4 = -ballSpeedY4;
ball4Y = BOX_HEIGHT - ball4Radius;
}
if ( Math.sqrt( (Math.pow((ball3X- ballX), 2)) + Math.pow((ball3Y-ballY), 2)) <= (ball3Radius + ballRadius)) {
System.exit(0);}
ball3X += ballSpeedX3;
ball3Y += ballSpeedY3;
if (ball3X - ball3Radius < 0) {
ballSpeedX3 = -ballSpeedX3;
ball3X = ball3Radius;
} else if (ball3X + ball3Radius > BOX_WIDTH) {
ballSpeedX3 = -ballSpeedX3;
ball3X = BOX_WIDTH - ball3Radius;
}
if (ball3Y - ball3Radius < 0) {
ballSpeedY3 = -ballSpeedY3;
ball3Y = ball3Radius;
} else if (ball3Y + ball3Radius > BOX_HEIGHT) {
ballSpeedY3 = -ballSpeedY3;
ball3Y = BOX_HEIGHT - ball3Radius;
}
ballX += ballSpeedX;
ballY += ballSpeedY;
if (ballX - ballRadius < 0) {
ballX = ballRadius;
} else if (ballX + ballRadius > BOX_WIDTH) {
ballX = BOX_WIDTH - ballRadius;
}
if (ballY - ballRadius < 0) {
ballY = ballRadius;
} else if (ballY + ballRadius > BOX_HEIGHT) {
ballY = BOX_HEIGHT - ballRadius;
}
ball1X += ballSpeed1X;
ball1Y += ballSpeed1Y;
if (ball1X - ballRadius1 < 0) {
ballSpeed1X = -ballSpeed1X;
ball1X = ballRadius1;
} else if (ball1X + ballRadius1 > BOX_WIDTH) {
ballSpeed1X = -ballSpeed1X;
ball1X = BOX_WIDTH - ballRadius1;
}
if (ball1Y - ballRadius1 < 0) {
ballSpeed1Y = -ballSpeed1Y;
ball1Y = ballRadius1;
} else if (ball1Y + ballRadius1 > BOX_HEIGHT) {
ballSpeed1Y = -ballSpeed1Y;
ball1Y = BOX_HEIGHT - ballRadius1;
}
ball2X += ballSpeed2X;
ball2Y += ballSpeed2Y;
if (ball2X - ballRadius2 < 0) {
ballSpeed2X = -ballSpeed2X;
ball2X = ballRadius2;
} else if (ball2X + ballRadius2 > BOX_WIDTH) {
ballSpeed2X = -ballSpeed2X;
ball2X = BOX_WIDTH - ballRadius2;
}
if (ball2Y - ballRadius2 < 0) {
ballSpeed2Y = -ballSpeed2Y;
ball2Y = ballRadius2;
} else if (ball2Y + ballRadius2 > BOX_HEIGHT) {
ballSpeed2Y = -ballSpeed2Y;
ball2Y = BOX_HEIGHT - ballRadius2;
}
repaint();
try {
Thread.sleep(1000 / UPDATE_RATE);
} catch (InterruptedException ex) { }
}
}
};
gameThread.start();
}
@Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
g.setColor(Color.BLACK);
g.fillRect(0, 0, BOX_WIDTH, BOX_HEIGHT);
g.setColor(Color.BLUE);
g.fillOval((int) (ballX - ballRadius), (int) (ballY - ballRadius),
(int)(2 * ballRadius), (int)(2 * ballRadius));
for(int i=100 ; i < 5 ; i++){ g.setColor(Color.RED);
g.fillOval((int) (ball1X - ballRadius1), (int) (ball1Y - ballRadius1),
(int)(2 * ballRadius1), (int)(2 * ballRadius1)); }
g.setColor(Color.PINK);
g.fillOval((int) (ball2X - ballRadius2), (int) (ball2Y - ballRadius2),
(int)(2 * ballRadius2), (int)(2 * ballRadius2));
g.setColor(Color.GREEN);
g.fillOval((int) (ball3X - ball3Radius), (int) (ball3Y - ball3Radius),
(int)(2 * ball3Radius), (int)(2 * ball3Radius));
for(int i=100 ; i < 5 ; i++){
g.setColor(Color.YELLOW);
g.fillOval((int) (ball4X - ball4Radius), (int) (ball4Y - ball4Radius),
(int)(2 * ball4Radius), (int)(2 * ball4Radius));}
}
public void keyPressed(KeyEvent e) {
if (e.getKeyCode() == KeyEvent.VK_RIGHT ) {
ballSpeedX = 5;
}
else if (e.getKeyCode() == KeyEvent.VK_LEFT ) {
ballSpeedX = -5;
}
else if (e.getKeyCode() == KeyEvent.VK_UP ) {
ballSpeedY = -5;
}
else if (e.getKeyCode() == KeyEvent.VK_DOWN ) {
ballSpeedY = 5;
}
}
public void keyReleased(KeyEvent e) {
if (e.getKeyCode() == KeyEvent.VK_RIGHT ) {
ballSpeedX = 0;
}
else if (e.getKeyCode() == KeyEvent.VK_LEFT ) {
ballSpeedX = 0;
}
else if (e.getKeyCode() == KeyEvent.VK_UP ) {
ballSpeedY = 0;
}
else if (e.getKeyCode() == KeyEvent.VK_DOWN ) {
ballSpeedY = 0;
}
}
public void keyTyped(KeyEvent e) { }
public static void main(String[] args) {
javax.swing.SwingUtilities.invokeLater(new Runnable() {
public void run() {
JFrame frame = new JFrame("Collision");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
Man man = new Man();
frame.setContentPane(man);
frame.pack();
frame.addKeyListener(man);
frame.setVisible(true);
}
});
}
}
你的代码对我来说有点长。不过看到你是新建线程调用Thread.sleep，我大概知道你错在哪里了
在您的新线程代码中，您正在更新球的位置（显示在 UI 上）和其他内容，对吗？这应该是您遇到问题的原因。
你不应该（通常不能）在任何线程中更新 UI，UI 线程除外。
为此，您可以使用 javax.swing.Timer 或 java.util.Timer。 IMO，前者更容易，更适合使用。
只需创建一个新计时器并调用 start:
// declare a timer variable in class level first!
timer = new Timer(1000 / UPDATE_RATE, new ActionListener() {
// all your code in the while loop...
// do not include the "while(true)" part
});
timer.start();
这是一个学校项目。我正在尝试进行碰撞游戏，目标是躲避球。我目前正在努力尝试每 30 秒左右添加一个球，但遇到了问题。我已经尝试了 for 循环和计时器来解决这部分（在我有 for 循环的代码中）。我反复得到相同的结果：球仍然在那里但看不见。如果有人知道如何解决此问题或可能有效的其他方法，请提供帮助。谢谢！
import java.awt.*;
import java.lang.*;
import java.awt.event.KeyEvent;
import java.util.Formatter;
import javax.swing.*;
import java.awt.event.*;
import java.awt.Polygon;
import java.awt.geom.Area;
public class Man extends JComponent implements KeyListener {
private static final int BOX_WIDTH = 640;
private static final int BOX_HEIGHT = 480;
private float ballSpeedX3 = 7;
private float ballSpeedY3 = 7;
private double ball3Radius = 20;
private double ball3X = 320 ;
private double ball3Y = 120 ;
private float ballSpeedX4 = -10;
private float ballSpeedY4 = 10;
private double ball4Radius = 15;
private double ball4X = 600 ;
private double ball4Y = 300 ;
private float ballSpeedX = 0;
private float ballSpeedY = 0;
private double ballRadius = 20;
private double ballX = 120;
private double ballY = 140;
private float ballSpeed1X = 10;
private float ballSpeed1Y = -10;
private double ballRadius1 = 20;
private double ball1X = 320;
private double ball1Y = 340;
private float ballSpeed2X = -3;
private float ballSpeed2Y = -3;
private double ballRadius2 = 50;
private double ball2X = 50;
private double ball2Y = 400;
private static final int UPDATE_RATE = 30;
public Man() {
this.setPreferredSize(new Dimension(BOX_WIDTH, BOX_HEIGHT));
Thread gameThread = new Thread() {
public void run() {
while(true){
if ( Math.sqrt( (Math.pow((ballX- ball1X), 2)) + Math.pow((ballY-ball1Y), 2)) <= (ballRadius1 + ballRadius)) {
System.exit(0);}
if ( Math.sqrt( (Math.pow((ball4X- ballX), 2)) + Math.pow((ball4Y-ballY), 2)) <= (ball4Radius + ballRadius)) {
System.exit(0);}
if ( Math.sqrt( (Math.pow((ball2X- ballX), 2)) + Math.pow((ball2Y-ballY), 2)) <= (ballRadius2 + ballRadius)) {
System.exit(0);}
ball4X += ballSpeedX4;
ball4Y += ballSpeedY4;
if (ball4X - ball4Radius < 0) {
ballSpeedX4 = -ballSpeedX4;
ball4X = ball4Radius;
} else if (ball4X + ball4Radius > BOX_WIDTH) {
ballSpeedX4 = -ballSpeedX4;
ball4X = BOX_WIDTH - ball4Radius;
}
if (ball4Y - ball4Radius < 0) {
ballSpeedY4 = -ballSpeedY4;
ball4Y = ball4Radius;
} else if (ball4Y + ball4Radius > BOX_HEIGHT) {
ballSpeedY4 = -ballSpeedY4;
ball4Y = BOX_HEIGHT - ball4Radius;
}
if ( Math.sqrt( (Math.pow((ball3X- ballX), 2)) + Math.pow((ball3Y-ballY), 2)) <= (ball3Radius + ballRadius)) {
System.exit(0);}
ball3X += ballSpeedX3;
ball3Y += ballSpeedY3;
if (ball3X - ball3Radius < 0) {
ballSpeedX3 = -ballSpeedX3;
ball3X = ball3Radius;
} else if (ball3X + ball3Radius > BOX_WIDTH) {
ballSpeedX3 = -ballSpeedX3;
ball3X = BOX_WIDTH - ball3Radius;
}
if (ball3Y - ball3Radius < 0) {
ballSpeedY3 = -ballSpeedY3;
ball3Y = ball3Radius;
} else if (ball3Y + ball3Radius > BOX_HEIGHT) {
ballSpeedY3 = -ballSpeedY3;
ball3Y = BOX_HEIGHT - ball3Radius;
}
ballX += ballSpeedX;
ballY += ballSpeedY;
if (ballX - ballRadius < 0) {
ballX = ballRadius;
} else if (ballX + ballRadius > BOX_WIDTH) {
ballX = BOX_WIDTH - ballRadius;
}
if (ballY - ballRadius < 0) {
ballY = ballRadius;
} else if (ballY + ballRadius > BOX_HEIGHT) {
ballY = BOX_HEIGHT - ballRadius;
}
ball1X += ballSpeed1X;
ball1Y += ballSpeed1Y;
if (ball1X - ballRadius1 < 0) {
ballSpeed1X = -ballSpeed1X;
ball1X = ballRadius1;
} else if (ball1X + ballRadius1 > BOX_WIDTH) {
ballSpeed1X = -ballSpeed1X;
ball1X = BOX_WIDTH - ballRadius1;
}
if (ball1Y - ballRadius1 < 0) {
ballSpeed1Y = -ballSpeed1Y;
ball1Y = ballRadius1;
} else if (ball1Y + ballRadius1 > BOX_HEIGHT) {
ballSpeed1Y = -ballSpeed1Y;
ball1Y = BOX_HEIGHT - ballRadius1;
}
ball2X += ballSpeed2X;
ball2Y += ballSpeed2Y;
if (ball2X - ballRadius2 < 0) {
ballSpeed2X = -ballSpeed2X;
ball2X = ballRadius2;
} else if (ball2X + ballRadius2 > BOX_WIDTH) {
ballSpeed2X = -ballSpeed2X;
ball2X = BOX_WIDTH - ballRadius2;
}
if (ball2Y - ballRadius2 < 0) {
ballSpeed2Y = -ballSpeed2Y;
ball2Y = ballRadius2;
} else if (ball2Y + ballRadius2 > BOX_HEIGHT) {
ballSpeed2Y = -ballSpeed2Y;
ball2Y = BOX_HEIGHT - ballRadius2;
}
repaint();
try {
Thread.sleep(1000 / UPDATE_RATE);
} catch (InterruptedException ex) { }
}
}
};
gameThread.start();
}
@Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
g.setColor(Color.BLACK);
g.fillRect(0, 0, BOX_WIDTH, BOX_HEIGHT);
g.setColor(Color.BLUE);
g.fillOval((int) (ballX - ballRadius), (int) (ballY - ballRadius),
(int)(2 * ballRadius), (int)(2 * ballRadius));
for(int i=100 ; i < 5 ; i++){ g.setColor(Color.RED);
g.fillOval((int) (ball1X - ballRadius1), (int) (ball1Y - ballRadius1),
(int)(2 * ballRadius1), (int)(2 * ballRadius1)); }
g.setColor(Color.PINK);
g.fillOval((int) (ball2X - ballRadius2), (int) (ball2Y - ballRadius2),
(int)(2 * ballRadius2), (int)(2 * ballRadius2));
g.setColor(Color.GREEN);
g.fillOval((int) (ball3X - ball3Radius), (int) (ball3Y - ball3Radius),
(int)(2 * ball3Radius), (int)(2 * ball3Radius));
for(int i=100 ; i < 5 ; i++){
g.setColor(Color.YELLOW);
g.fillOval((int) (ball4X - ball4Radius), (int) (ball4Y - ball4Radius),
(int)(2 * ball4Radius), (int)(2 * ball4Radius));}
}
public void keyPressed(KeyEvent e) {
if (e.getKeyCode() == KeyEvent.VK_RIGHT ) {
ballSpeedX = 5;
}
else if (e.getKeyCode() == KeyEvent.VK_LEFT ) {
ballSpeedX = -5;
}
else if (e.getKeyCode() == KeyEvent.VK_UP ) {
ballSpeedY = -5;
}
else if (e.getKeyCode() == KeyEvent.VK_DOWN ) {
ballSpeedY = 5;
}
}
public void keyReleased(KeyEvent e) {
if (e.getKeyCode() == KeyEvent.VK_RIGHT ) {
ballSpeedX = 0;
}
else if (e.getKeyCode() == KeyEvent.VK_LEFT ) {
ballSpeedX = 0;
}
else if (e.getKeyCode() == KeyEvent.VK_UP ) {
ballSpeedY = 0;
}
else if (e.getKeyCode() == KeyEvent.VK_DOWN ) {
ballSpeedY = 0;
}
}
public void keyTyped(KeyEvent e) { }
public static void main(String[] args) {
javax.swing.SwingUtilities.invokeLater(new Runnable() {
public void run() {
JFrame frame = new JFrame("Collision");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
Man man = new Man();
frame.setContentPane(man);
frame.pack();
frame.addKeyListener(man);
frame.setVisible(true);
}
});
}
}
你的代码对我来说有点长。不过看到你是新建线程调用Thread.sleep，我大概知道你错在哪里了
在您的新线程代码中，您正在更新球的位置（显示在 UI 上）和其他内容，对吗？这应该是您遇到问题的原因。
你不应该（通常不能）在任何线程中更新 UI，UI 线程除外。
为此，您可以使用 javax.swing.Timer 或 java.util.Timer。 IMO，前者更容易，更适合使用。
只需创建一个新计时器并调用 start:
// declare a timer variable in class level first!
timer = new Timer(1000 / UPDATE_RATE, new ActionListener() {
// all your code in the while loop...
// do not include the "while(true)" part
});
timer.start();