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我很困惑爲什麼這段代碼不會讓第二個球移動。我的目標是擁有兩個球，而你正在控制其中一個，另一個只是隨機彈跳。現在我被卡在箭頭鍵球上。我不明白爲什麼它不通過箭頭鍵移動。JAVA爲什麼我的第二圈移動箭頭鍵
import java.awt.*;
import java.awt.event.KeyEvent;
import java.util.Formatter;
import javax.swing.*;
/**
* One ball bouncing inside a rectangular box.
* All codes in one file. Poor design!
*/
// Extends JPanel, so as to override the paintComponent() for custom rendering codes.
public class Man extends JPanel {
// Container box's width and height
private static final int BOX_WIDTH = 640;
private static final int BOX_HEIGHT = 480;
private boolean upPressed = false;
private boolean downPressed = false;
private boolean leftPressed = false;
private boolean rightPressed = false;
// Ball's properties
private float ballRadius = 20; // Ball's radius
private float ballX = ballRadius + 50; // Ball's center (x, y)
private float ballY = ballRadius + 20;
private float ballSpeedX = 3; // Ball's speed for x and y
private float ballSpeedY = 2;
// ball # 2
public float ballSpeedX2 = 0;
public float ballSpeedY2 = 0;
private float ball2Radius = 20; // Ball's radius
private float ball2X = 320; // Ball's center (x, y)
private float ball2Y = 240;
private static final int UPDATE_RATE = 30; // Number of refresh per second
/** Constructor to create the UI components and init game objects. */
public Man() {
this.setPreferredSize(new Dimension(BOX_WIDTH, BOX_HEIGHT));
// Start the ball bouncing (in its own thread)
Thread gameThread = new Thread() {
public void step(){
ball2X += ballSpeedX2;
ball2Y += ballSpeedY2;
if (rightPressed) {
ballSpeedX2+=5;
}
if (leftPressed) {
ballSpeedX2-=5;
}
if (upPressed) {
ballSpeedY2-=5;
}
if (downPressed) {
ballSpeedY2+=5;
}
repaint();
try {
Thread.sleep(1000/UPDATE_RATE); // milliseconds
} catch (InterruptedException ex) { }
}
public void run() {
while (true) {
// Execute one update step
// Calculate the ball's new position
ballX += ballSpeedX;
ballY += ballSpeedY;
// Check if the ball moves over the bounds
// If so, adjust the position and speed.
if (ballX - ballRadius < 0) {
ballSpeedX = -ballSpeedX; // Reflect along normal
ballX = ballRadius; // Re-position the ball at the edge
} else if (ballX + ballRadius > BOX_WIDTH) {
ballSpeedX = -ballSpeedX;
ballX = BOX_WIDTH - ballRadius;
}
// May cross both x and y bounds
if (ballY - ballRadius < 0) {
ballSpeedY = -ballSpeedY;
ballY = ballRadius;
} else if (ballY + ballRadius > BOX_HEIGHT) {
ballSpeedY = -ballSpeedY;
ballY = BOX_HEIGHT - ballRadius;
}
// Refresh the display
repaint(); // Callback paintComponent()
// Delay for timing control and give other threads a chance
try {
Thread.sleep(1000/UPDATE_RATE); // milliseconds
} catch (InterruptedException ex) { }
}
}
};
在後面的代碼：
gameThread.start(); // Callback run()
}
/** Custom rendering codes for drawing the JPanel */
@Override
public void paintComponent(Graphics g) {
super.paintComponent(g); // Paint background
// Draw the box
g.setColor(Color.BLACK);
g.fillRect(0, 0, BOX_WIDTH, BOX_HEIGHT);
// Draw the ball
g.setColor(Color.BLUE);
g.fillOval((int) (ballX - ballRadius), (int) (ballY - ballRadius),
(int)(2 * ballRadius), (int)(2 * ballRadius));
// Display the ball's information
g.setColor(Color.WHITE);
g.setFont(new Font("Courier New", Font.PLAIN, 12));
StringBuilder sb = new StringBuilder();
Formatter formatter = new Formatter(sb);
formatter.format("Ball @(%3.0f,%3.0f) Speed=(%2.0f,%2.0f)", ballX, ballY,
ballSpeedX, ballSpeedY);
g.drawString(sb.toString(), 20, 30);
g.setColor(Color.BLUE);
g.fillOval((int) (ball2X - ball2Radius), (int) (ball2Y - ball2Radius),
(int)(2 * ball2Radius), (int)(2 * ball2Radius));
g.setColor(Color.RED);
g.setFont(new Font("Courier New", Font.PLAIN, 12));
g.drawString(sb.toString(), 20, 30);
g.setColor(Color.GREEN);
}
public void keyPressed(KeyEvent e) {
if (e.getKeyCode() == KeyEvent.VK_RIGHT) {
rightPressed = true;
} else if (e.getKeyCode() == KeyEvent.VK_LEFT) {
leftPressed = true;
} else if (e.getKeyCode() == KeyEvent.VK_UP) {
upPressed = true;
} else if (e.getKeyCode() == KeyEvent.VK_DOWN) {
downPressed = true;
}
repaint();
try {
Thread.sleep(1000/UPDATE_RATE); // milliseconds
} catch (InterruptedException ex) { }
}
public void keyReleased(KeyEvent e) {
if (e.getKeyCode() == KeyEvent.VK_RIGHT) {
rightPressed = false;
} else if (e.getKeyCode() == KeyEvent.VK_LEFT) {
leftPressed = false;
} else if (e.getKeyCode() == KeyEvent.VK_UP) {
upPressed = false;
} else if (e.getKeyCode() == KeyEvent.VK_DOWN) {
downPressed = false;
try {
Thread.sleep(1000/UPDATE_RATE); // milliseconds
} catch (InterruptedException ex) { }
}
}
public void keyTyped(KeyEvent e) {}
/** main program (entry point) */
public static void main(String[] args) {
// Run GUI in the Event Dispatcher Thread (EDT) instead of main thread.
javax.swing.SwingUtilities.invokeLater(new Runnable() {
public void run() {
// Set up main window (using Swing's Jframe)
JFrame frame = new JFrame("A Bouncing Ball");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setContentPane(new Man());
frame.pack();
frame.setVisible(true);
}
});
}
}
如果您將代碼縮減爲您認爲應該幫助您實現的部分並添加一些更詳細的說明，它將會很好。 – ChiefTwoPencils
你在代碼中使用'keyPressed（）'，'keyReleased（）'方法的地方？ – DimaSan
[如何使用密鑰綁定而不是密鑰監聽器]的可能重複（http://stackoverflow.com/questions/22741215/how-to-use-key-bindings-instead-of-key-listeners） – user1803551