我正在尝试编写一个程序，在该程序中，从字符（绿色正方形）到光标位置绘制一条线，该线每当字符移动时都会更新，但该线不会显示。其他所有内容都会创建一个新的Panel或JFrame。
我使用了绘画功能，但所做的只是创建一个新框架。当前的绘画功能仅具有测试线，因为我认为我能够使用mouseX和mouseY位置绘制该线而没有太大问题。
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.Timer;
import javax.swing.*;
import java.awt.*;
import java.awt.geom.*;
public class SquareToCursor extends JPanel implements ActionListener, KeyListener {
// Global Constants
public static final int FIELD_WIDTH = 1920;
public static final int FIELD_HEIGHT = 1080;
private static final int PLAYER_MAX = 20;
private static final double PLAYER_VELOCITY = 0.5;
// Global Variables
boolean paused = false, shoot = false;
boolean movingUp = false, movingDown = false;
boolean onPlatform = false;
private boolean pressedLeft = false, pressedRight = false, pressedUp = false, pressedDown = false, pressedCtrl = false;
private boolean movingLeft = false, movingRight = false;
double playerSpeed = 0;
double playerSpeed2 = 0;
// Local Constants
private final int TIMER_SPEED = 10;
private static JFrame gameFrame;
private Timer timer;
private int playerX, playerY;
private JLabel pause = new JLabel("GAME PAUSED");
private Font fontPaused = new Font("Helvetica", Font.BOLD, 50);
private int textWidth2 = pause.getFontMetrics(fontPaused).stringWidth(pause.getText());
private JLabel player = new JLabel();
private JLabel lblGameOver = new JLabel("Game Over!");
private Font fontGameOver = new Font("Helvetica", Font.BOLD, 24);
private int textWidth = lblGameOver.getFontMetrics(fontGameOver).stringWidth(lblGameOver.getText());
public void paintComponent(Graphics g)
{
//vertical line
g.setColor(Color.red);
g.drawLine(20, 20, 20, 120);
//horizontal line
g.setColor(Color.green);
g.drawLine(20, 20, 120, 20);
//diagonal line
g.setColor(Color.blue);
g.drawLine(20, 20, 120, 120);
}
public static void main (String[] args)
{
SquareToCursor panel = new SquareToCursor();
gameFrame.add(panel);
gameFrame.setVisible(true);
}
// Constructor
public SquareToCursor() {
gameFrame = new JFrame();
// Set the background image and other JFrame properties
//gameFrame.setContentPane(new JLabel(backdrop));
gameFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
gameFrame.setSize(1920, 1080);
// gameFrame.setExtendedState(JFrame.MAXIMIZED_BOTH);
gameFrame.setTitle("Knockback");
gameFrame.setLocationRelativeTo(null);
gameFrame.setResizable(false);
gameFrame.setFocusable(true);
gameFrame.setLayout(null);
gameFrame.setVisible(true);
player.setSize(100, 100);
player.setLocation(gameFrame.getWidth() / 2 - player.getWidth(), gameFrame.getHeight() / 2 - player.getHeight());
player.setOpaque(true);
player.setBackground(Color.GREEN);
gameFrame.add(player);
// pause/un-pause game
pause.setSize(textWidth2, 100);
pause.setLocation(FIELD_WIDTH / 2 - textWidth2 / 2, FIELD_HEIGHT / 2 - 100);
pause.setFont(fontPaused);
pause.setForeground(Color.BLUE);
pause.setVisible(false);
gameFrame.add(pause);
// Set up the "Game Over" JLabel
lblGameOver.setVisible(false);
lblGameOver.setSize(400, 100);
lblGameOver.setLocation(FIELD_WIDTH / 2 - textWidth / 2, FIELD_HEIGHT / 2 - 50);
lblGameOver.setFont(fontGameOver);
lblGameOver.setForeground(Color.RED);
gameFrame.addKeyListener(this);
timer = new Timer(TIMER_SPEED, this);
timer.start();
}
@override
public void actionPerformed(ActionEvent event) {
playerX = player.getX();
playerY = player.getY();
if (pressedLeft && !movingRight) {
playerSpeed += PLAYER_VELOCITY;
if (playerSpeed > PLAYER_MAX)
playerSpeed = PLAYER_MAX;
playerX -= playerSpeed;
movingLeft = true;
}
else if (pressedRight && !movingLeft) {
playerSpeed += PLAYER_VELOCITY;
if (playerSpeed > PLAYER_MAX)
playerSpeed = PLAYER_MAX;
playerX += playerSpeed;
movingRight = true;
}
else if (!(pressedRight) && movingRight && playerSpeed > 0) {
playerSpeed -= 0.4;
playerX += playerSpeed;
if (playerSpeed < 0.5) {
movingRight = false;
}
}
else if (!(pressedLeft) && movingLeft && playerSpeed >= 0) {
playerSpeed -= 0.4;
playerX -= playerSpeed;
if (playerSpeed < 0.5) {
movingLeft = false;
}
}
if (pressedUp && !movingDown) {
playerSpeed2 += PLAYER_VELOCITY;
if (playerSpeed2 > PLAYER_MAX)
playerSpeed2 = PLAYER_MAX;
playerY -= playerSpeed2;
movingUp = true;
}
else if (pressedDown && !movingUp) {
playerSpeed2 += PLAYER_VELOCITY;
if (playerSpeed2 > PLAYER_MAX)
playerSpeed2 = PLAYER_MAX;
playerY += playerSpeed2;
movingDown = true;
}
else if (!(pressedDown) && movingDown && playerSpeed2 > 0) {
playerSpeed2 -= 0.4;
playerY += playerSpeed2;
if (playerSpeed2 < 0.5) {
movingDown = false;
}
}
else if (!(pressedUp) && movingUp && playerSpeed2 >= 0) {
playerSpeed2 -= 0.4;
playerY -= playerSpeed2;
if (playerSpeed2 < 0.5) {
movingUp = false;
}
}
if (player.getX() > gameFrame.getWidth()) {
playerX = 0 - player.getWidth();
}
if (player.getX() < 0 - player.getWidth()) {
playerX = gameFrame.getWidth();
}
if (player.getY() > gameFrame.getHeight()) {
playerY = 0 - player.getHeight();
}
if (player.getY() < 0 - player.getHeight()) {
playerY = gameFrame.getHeight();
}
player.setLocation((int)playerX, (int)playerY);
}
@Override
public void keyPressed(KeyEvent event) {
// TODO Auto-generated method stub
int key = event.getKeyCode();
if (key == KeyEvent.VK_A) // LEFT arrow
{
pressedLeft = true;
pressedRight = false;
}
if (key == KeyEvent.VK_D) // RIGHT arrow
{
pressedRight = true;
pressedLeft = false;
}
if (key == KeyEvent.VK_W)
{
pressedUp = true;
pressedDown = false;
}
if (key == KeyEvent.VK_CONTROL) // control key
pressedCtrl = true;
if (key == KeyEvent.VK_X) {
if (pressedCtrl)
gameFrame.dispose();
}
if (shoot == false && key == KeyEvent.VK_ENTER) {
shoot = true;
}
if (key == KeyEvent.VK_S)
{
pressedDown = true;
pressedUp = false;
}
if (key == KeyEvent.VK_ESCAPE) {
if (!paused) {
timer.stop();
paused = true;
pause.setVisible(true);
} else {
timer.start();
paused = false;
pause.setVisible(false);
}
}
}
@Override
public void keyReleased(KeyEvent event) {
// TODO Auto-generated method stub
int key = event.getKeyCode();
if (key == KeyEvent.VK_A) // LEFT arrow
pressedLeft = false;
if (key == KeyEvent.VK_D) // RIGHT arrow
pressedRight = false;
if (key == KeyEvent.VK_W || key == KeyEvent.VK_SPACE)
pressedUp = false;
if (key == KeyEvent.VK_CONTROL) // control key
pressedCtrl = false;
if (key == KeyEvent.VK_ENTER) {
shoot = false;
}
if (key == KeyEvent.VK_S)
{
pressedDown = false;
}
}
@Override
public void keyTyped(KeyEvent e) {
// TODO Auto-generated method stub
}
}
我希望线条显示在框架上，但事实并非如此。它们不会出现在任何地方。