数组不是我的强项，我通常必须经历很多错误，通常是 IndexOutOfBoundsException，然后才能得到正确的结果。这次我得到的错误是一遍又一遍。
Exception in thread "AWT-EventQueue-0" java.lang.IndexOutOfBoundsException: Index: 0, Size: 0
at java.util.ArrayList.RangeCheck(ArrayList.java:547)
at java.util.ArrayList.get(ArrayList.java:322)
at FinalSnake$DrawPanel.paintComponent(FinalSnake.java:272)
at javax.swing.JComponent.paint(JComponent.java:1037)
at javax.swing.JComponent._paintImmediately(JComponent.java:5106)
at javax.swing.JComponent.paintImmediately(JComponent.java:4890)
at javax.swing.RepaintManager$3.run(RepaintManager.java:814)
at javax.swing.RepaintManager$3.run(RepaintManager.java:802)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlContext.java:86)
at javax.swing.RepaintManager.paintDirtyRegions(RepaintManager.java:802)
at javax.swing.RepaintManager.paintDirtyRegions(RepaintManager.java:745)
at javax.swing.RepaintManager.prePaintDirtyRegions(RepaintManager.java:725)
at javax.swing.RepaintManager.access$1000(RepaintManager.java:46)
at javax.swing.RepaintManager$ProcessingRunnable.run(RepaintManager.java:1680)
at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:209)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:715)
at java.awt.EventQueue.access$400(EventQueue.java:82)
at java.awt.EventQueue$2.run(EventQueue.java:676)
at java.awt.EventQueue$2.run(EventQueue.java:674)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlContext.java:86)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:685)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:296)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:211)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:201)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:196)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:188)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)
当我在程序中使用这段代码时，它用于绘制蛇的 body 。
/* Sprite: Snake Body */
if (length > 0) {
for (int i = 0; i <= length; i++) {
g.setColor(Color.darkGray);
g.fillRect(bodyX.get(i), bodyY.get(i), width, height);
}
}
每当我收到这些错误时，我永远无法理解程序试图告诉我什么 XD
这是其余的代码
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.util.Random;
import java.util.ArrayList;
public class FinalSnake extends JFrame {
String direction = "right";
//String duration =
int time = 100;
int start = 0;
/* Sprite: snake head co-ordinates */
int x = 400;
int y = 450;
int width = 10;
int height = 10;
/* Sprite: snake body */
int length = 0;
ArrayList<Integer> bodyX = new ArrayList<Integer>();
ArrayList<Integer> bodyY = new ArrayList<Integer>();
/* Score */
int point = 0;
String p = String.valueOf(point);
/* Sprite: mouse co-ordinates */
Random rand = new Random();
int addx = (rand.nextInt(10)) * 10;
int addy = (rand.nextInt(10)) * 10;
int mx = ((rand.nextInt(5) + 1) * 100) + addx;
int my = ((rand.nextInt(6) + 2) * 100) + addy;
DrawPanel drawPanel = new DrawPanel();
Timer timer;
public FinalSnake() {
addMouseListener(new MouseListenerfinal());
timer = new Timer(time, new TimerListener()); ////////////// <<<<<<<<<<<<<<<<<< TIMER
timer.start();
/* move snake up */
Action upAction = new AbstractAction() {
public void actionPerformed(ActionEvent e) {
direction = "up"; ////////////// <<<<<<<<<<<<<<<<<< direction only change
}
};
/* move snake down */
Action downAction = new AbstractAction() {
public void actionPerformed(ActionEvent e) {
direction = "down";
}
};
/* move snake left */
Action leftAction = new AbstractAction() {
public void actionPerformed(ActionEvent e) {
direction = "left";
}
};
/* move snake right */
Action rightAction = new AbstractAction() {
public void actionPerformed(ActionEvent e) {
direction = "right";
}
};
InputMap inputMap = drawPanel
.getInputMap(JPanel.WHEN_IN_FOCUSED_WINDOW);
ActionMap actionMap = drawPanel.getActionMap();
inputMap.put(KeyStroke.getKeyStroke("RIGHT"), "rightAction");
actionMap.put("rightAction", rightAction);
inputMap.put(KeyStroke.getKeyStroke("LEFT"), "leftAction");
actionMap.put("leftAction", leftAction);
inputMap.put(KeyStroke.getKeyStroke("DOWN"), "downAction");
actionMap.put("downAction", downAction);
inputMap.put(KeyStroke.getKeyStroke("UP"), "upAction");
actionMap.put("upAction", upAction);
add(drawPanel);
pack();
setDefaultCloseOperation(EXIT_ON_CLOSE);
setLocationRelativeTo(null);
setVisible(true);
}// FinalSnake()
private class TimerListener implements ActionListener {
public void actionPerformed(ActionEvent e) { /////////////////// <<<<<<<<<<<<<< All logic here
if ("right".equals(direction)) {
x += 10;
if (x >= mx && x <= mx + 9 && y >= my && y <= my + 9) {
addx = (rand.nextInt(10)) * 10;
addy = (rand.nextInt(10)) * 10;
mx = ((rand.nextInt(5) + 1) * 100) + addx;
my = ((rand.nextInt(6) + 1) * 100) + addy;
point += 100;
p = String.valueOf(point);
length++;
time--;
bodyY.add(0, y);
bodyX.add(0, x);
//System.out.println(bodyX + ":" + bodyY);
}
if (x > 699) {
new GameOver();
dispose();
}
} else if ("left".equals(direction)) {
x -= 10;
if (x >= mx && x <= mx + 9 && y >= my && y <= my + 9) {
addx = (rand.nextInt(10)) * 10;
addy = (rand.nextInt(10)) * 10;
mx = ((rand.nextInt(5) + 1) * 100) + addx;
my = ((rand.nextInt(6) + 1) * 100) + addy;
point += 100;
p = String.valueOf(point);
length++;
time--;
bodyY.add(0, y);
bodyX.add(0, x);
}
if (x < 99) {
new GameOver();
dispose();
}
} else if ("up".equals(direction)) {
y -= 10;
if (y >= my && y <= my + 9 && x >= mx && x <= mx + 9) {
addx = (rand.nextInt(10)) * 10;
addy = (rand.nextInt(10)) * 10;
mx = ((rand.nextInt(5) + 1) * 100) + addx;
my = ((rand.nextInt(6) + 1) * 100) + addy;
point += 100;
p = String.valueOf(point);
length++;
time--;
bodyY.add(0, y);
bodyX.add(0, x);
}
if (y < 99) {
new GameOver();
dispose();
}
} else if ("down".equals(direction)) {
y += 10;
if (y >= my && y <= my + 9 && x >= mx && x <= mx + 9) {
addx = (rand.nextInt(10)) * 10;
addy = (rand.nextInt(10)) * 10;
mx = ((rand.nextInt(5) + 1) * 100) + addx;
my = ((rand.nextInt(6) + 1) * 100) + addy;
point += 100;
p = String.valueOf(point);
length++;
time--;
bodyY.add(0, y);
bodyX.add(0, x);
}
if (y > 799) {
new GameOver();
dispose();
}
}
drawPanel.repaint();
}
}
private class GameOver extends JFrame implements ActionListener {
JLabel answer = new JLabel("");
JPanel pane = new JPanel(); // create pane object
JButton pressme = new JButton("Quit");
JButton replay = new JButton("Replay?");
GameOver() // the constructor
{
super("Game Over");
timer.stop(); ////////////////////// <<<<<<<<<< Stop TIMER
setBounds(100, 100, 300, 200);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
Container con = this.getContentPane(); // inherit main frame
con.add(pane);
pressme.setMnemonic('Q'); // associate hotkey
pressme.addActionListener(this); // register button listener
replay.addActionListener(this);
pane.add(answer);
pane.add(pressme);
pane.add(replay);
pressme.requestFocus();
answer.setText("You Lose");
setVisible(true); // make frame visible
}// GameOver()
// here is the basic event handler
public void actionPerformed(ActionEvent event) {
Object source = event.getSource();
if (source == pressme)
System.exit(0);
if (source == replay) {
dispose();
EventQueue.invokeLater(new Runnable() {
public void run() {
new FinalSnake();
}
});
}
}// actionPreformed
}// GameOver
private class DrawPanel extends JPanel {
protected void paintComponent(Graphics g) {
super.paintComponent(g);
if (start == 1){
g.setColor(Color.white);
}
Font ith = new Font("Ithornît", Font.BOLD, 78);
/* Background: Snake */
g.setColor(Color.darkGray);
g.fillRect(0, 0, getWidth(), getHeight());
g.setColor(Color.gray);
g.fillRect(100, 100, 600, 700);
g.setColor(Color.white);
g.drawRect(99, 99, 601, 701);
g.drawString("Quit", 102, 86);
g.drawRect(100, 70, 30, 20);
//g.drawString("Pause", 152, 86);
//g.drawRect(150, 70, 40, 20);
g.drawString("Score: ", 602, 86);
g.drawString(p, 640, 86);
g.setFont(ith);
g.drawString("SNAKE", 350, 60);
/* Sprite: Mouse */
g.setColor(Color.black);
g.fillRect(mx, my, width, height);
/* Sprite: Snake Body */
if (length > 0) {
for (int i = 0; i < length; i++) {
g.setColor(Color.darkGray);
g.fillRect(bodyX.get(i), bodyY.get(i), width, height);
}
}
/* Sprite: Snake head */
g.setColor(Color.white);
g.fillRect(x, y, width, height);
}// Paint Component
public Dimension getPreferredSize() {
return new Dimension(800, 850);
}// Dimension
}// DrawPanel
public static void main(String[] args) {
//new StartScreen();
EventQueue.invokeLater(new Runnable() {
public void run() {
new FinalSnake();
}
});
}// main
}// Snake Class
/* Tracks where mouse is clicked */
class MouseListenerfinal extends MouseAdapter {
public void mouseReleased(MouseEvent me) {
if (me.getX() >= 101 && me.getX() <= 131 && me.getY() >= 94
&& me.getY() <= 115) {
System.exit(0);
}
if (me.getX() >= 151 && me.getX() <= 181 && me.getY() >= 94
&& me.getY() <= 115) {
}
String str = "Mouse Released at " + me.getX() + "," + me.getY();
System.out.println(str);
}
}// MouseAdapter
最佳答案
更改for (int i = 0; i <= length; i++) {至for (int i = 0; i < length; i++) { ，因为 ArrayList 从索引 0 开始并以 size()-1 结束.
关于java - 在绘制组件中使用数组来循环蛇的 body ，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/21094816/