我需要有关 java.lang.IndexOutOfBoundsException - ArrayList 的帮助

Question

我正在做一个关于吉他英雄克隆的项目。当我运行我的游戏（只是概念）时发生错误：java.lang.IndexOutOfBoundsException。

package tapnstrum2;

import java.awt.*;
import java.awt.event.*;
import java.io.FileNotFoundException;
import java.util.ArrayList;
import javax.swing.*;

public class String1 extends JFrame implements ActionListener {
Image S1;
GNode G;
PlayIG P;
int m =0;

public String1(){
    ImageIcon S1i = new ImageIcon("D:\\JavaProject\\Graphic-library\\buttons\\String01.png");
    S1 = S1i.getImage();
}
public Image getImage(){
    return S1;
}

public void keyPressed(KeyEvent e) throws FileNotFoundException, InterruptedException{
    ArrayList GNodes = P.getGNodes();
    GNode GN = (GNode) GNodes.get(m);
    int key = e.getKeyCode();
    ImageIcon S1iExact = new ImageIcon("D:\\JavaProject\\Graphic-library\\buttons\\String01_Exact.png");
    ImageIcon S1iMissed = new ImageIcon("D:\\JavaProject\\Graphic-library\\buttons\\String01_Missed.png");
    if (key == KeyEvent.VK_F1){
        for (int i=0; i< GNodes.size(); i++){
        if (GN.getY()+47>=380 && GN.getY()+47<=420)
            S1 = S1iExact.getImage();
        else
            S1 = S1iMissed.getImage();
        }
    }
    m++;
if (m>=GN.size())
 m=0;
}
public void keyReleased(KeyEvent e){
        int key = e.getKeyCode();
        ImageIcon S1i = new ImageIcon("D:\\JavaProject\\Graphic-library\\buttons\\String01.png");
        if (key == KeyEvent.VK_F1){
           S1 = S1i.getImage();
        }
}

@Override
public void actionPerformed(ActionEvent ae) {
    repaint();
}

}

我试图从一个从简单文本文件中读取的 ArrayList 中获取图像的边界，每行仅包含 0 或 1 个（1 是 drawImage，0 不是）并检查边界。 此错误的索引可能等于我按 F1 的次数。虽然我试图在最后几行中为 m 设置条件。

更新我的错误信息：

Exception in thread "AWT-EventQueue-0" java.lang.IndexOutOfBoundsException: Index: 3, Size: 2
    at java.util.ArrayList.rangeCheck(ArrayList.java:653)
    at java.util.ArrayList.get(ArrayList.java:429)
    at tapnstrum2.String1.keyPressed(String1.java:28)
    at tapnstrum2.PlayIG$AL.keyPressed(PlayIG.java:98)
    at java.awt.Component.processKeyEvent(Component.java:6483)
    at javax.swing.JComponent.processKeyEvent(JComponent.java:2832)
    at java.awt.Component.processEvent(Component.java:6302)
    at java.awt.Container.processEvent(Container.java:2234)
    at java.awt.Component.dispatchEventImpl(Component.java:4881)
    at java.awt.Container.dispatchEventImpl(Container.java:2292)
    at java.awt.Component.dispatchEvent(Component.java:4703)
    at java.awt.KeyboardFocusManager.redispatchEvent(KeyboardFocusManager.java:1954)
    at java.awt.DefaultKeyboardFocusManager.dispatchKeyEvent(DefaultKeyboardFocusManager.java:806)
    at java.awt.DefaultKeyboardFocusManager.preDispatchKeyEvent(DefaultKeyboardFocusManager.java:1074)
    at java.awt.DefaultKeyboardFocusManager.typeAheadAssertions(DefaultKeyboardFocusManager.java:945)
    at java.awt.DefaultKeyboardFocusManager.dispatchEvent(DefaultKeyboardFocusManager.java:771)
    at java.awt.Component.dispatchEventImpl(Component.java:4752)
    at java.awt.Container.dispatchEventImpl(Container.java:2292)
    at java.awt.Window.dispatchEventImpl(Window.java:2750)
    at java.awt.Component.dispatchEvent(Component.java:4703)
    at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:758)
    at java.awt.EventQueue.access$500(EventQueue.java:97)
    at java.awt.EventQueue$3.run(EventQueue.java:709)
    at java.awt.EventQueue$3.run(EventQueue.java:703)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:75)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:86)
    at java.awt.EventQueue$4.run(EventQueue.java:731)
    at java.awt.EventQueue$4.run(EventQueue.java:729)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:75)
    at java.awt.EventQueue.dispatchEvent(EventQueue.java:728)
    at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:201)
    at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116)
    at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:105)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93)
    at java.awt.EventDispatchThread.run(EventDispatchThread.java:82)

如果有什么有用的可以下载我的项目 https://mega.co.nz/#F!ql80jDKY!fM91p7phB7LfhTs75rSK-Q

Answer 1

您需要检查 m 是否小于此行中 GNodes ArrayList 的大小：

GNode GN = (GNode) GNodes.get(m); //NetBeans inform this line contain an error

错误表示m在ArrayList的范围之外，这只是意味着它要么等于或大于ArrayList的长度，要么小于0。

例如，

当 m 为 3 且您的 ArrayList 为 [x, y, z] 时

GNodes.get(m) 尝试获取z 之后的值，该值不存在并导致 Java 抛出异常。

Answer 2

问题出在这一行：

GNode GN = (GNode) GNodes.get(m);

如果索引m 是> GNodes.size()，那么它将抛出该异常。你有两个选择：

1. 将该语句添加到 try/catch 块中。

2. 添加 if 语句：

   GNode GN = null;
   if (m > 0 && m < GNodes.size()) {
       GN = (GNode) GNodes.get(m);
   }
   

Answer 3

我发现了我的问题。每次我从 ArrayList 中删除一个元素时，它后面的元素都会自动向上推。在我的程序中，每当一个节点到达框架的底部时，它就会消失并从该 ArrayList 中删除。所以我需要检查的索引只是 0，即 ArrayList 的第一个元素。现在我可以修复了。非常感谢大家帮助我找出答案。 :)

public void keyPressed(KeyEvent e) throws FileNotFoundException, InterruptedException{
    ArrayList GNodes = PlayIG.getGNodes();
    GNode GN = (GNode) GNodes.get(0);
    System.out.println("" + m + " " + GNodes);
    int key = e.getKeyCode();
    ImageIcon S1iExact = new ImageIcon("D:\\JavaProject\\Graphic-library\\buttons\\String01_Exact.png");
    ImageIcon S1iMissed = new ImageIcon("D:\\JavaProject\\Graphic-library\\buttons\\String01_Missed.png");
    if (key == KeyEvent.VK_F1){
            if (GN.getY()+47>=370 && GN.getY()+47<=420)
                S1 = S1iExact.getImage();
            else
                S1 = S1iMissed.getImage();

    }