java - 线程中的异常 "AWT-EventQueue-0"java.lang.ArrayIndexOutOfBoundsException : No such child

Question

enter image description here嗯..我做了一个简单的射击游戏，但遇到了问题。这个异常。

Exception in thread "AWT-EventQueue-0" java.lang.ArrayIndexOutOfBoundsException: No such child: 22
  at java.awt.Container.getComponent(Container.java:334)
  at javax.swing.JComponent.rectangleIsObscured(JComponent.java:4390)
  at javax.swing.JComponent.paint(JComponent.java:1054)
  at javax.swing.JComponent.paintToOffscreen(JComponent.java:5210)
  at javax.swing.RepaintManager$PaintManager.paintDoubleBuffered(RepaintManager.java:1579)
  at javax.swing.RepaintManager$PaintManager.paint(RepaintManager.java:1502)
  at javax.swing.RepaintManager.paint(RepaintManager.java:1272)
  at javax.swing.JComponent._paintImmediately(JComponent.java:5158)
  at javax.swing.JComponent.paintImmediately(JComponent.java:4969)
  at javax.swing.RepaintManager$4.run(RepaintManager.java:831)
  at javax.swing.RepaintManager$4.run(RepaintManager.java:814)
  at java.security.AccessController.doPrivileged(Native Method)
  at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:80)
  at javax.swing.RepaintManager.paintDirtyRegions(RepaintManager.java:814)
  at javax.swing.RepaintManager.paintDirtyRegions(RepaintManager.java:789)
  at javax.swing.RepaintManager.prePaintDirtyRegions(RepaintManager.java:738)
  at javax.swing.RepaintManager.access$1200(RepaintManager.java:64)
  at javax.swing.RepaintManager$ProcessingRunnable.run(RepaintManager.java:1732)
  at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:311)
  at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:756)
  at java.awt.EventQueue.access$500(EventQueue.java:97)
  at java.awt.EventQueue$3.run(EventQueue.java:709)
  at java.awt.EventQueue$3.run(EventQueue.java:703)
  at java.security.AccessController.doPrivileged(Native Method)
  at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:80)
  at java.awt.EventQueue.dispatchEvent(EventQueue.java:726)
  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)

如果有异常的话，当我射出很多子弹时会出现异常。这是什么？我不知道出了什么问题，因为它运行良好。

package com.thread;

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;

public class ShootingGame extends JFrame{
    Container c;
    Enemy enemy;
    Thread th;
    public ShootingGame() {
        setTitle("Shooting Game");
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setSize(500,360);
        c = getContentPane();

        enemy = new Enemy(new ImageIcon("images/enemy_plane.png"));
        Player player = new Player(new ImageIcon("images/player.png"));

        c.add(player, BorderLayout.SOUTH);
        c.add(enemy, BorderLayout.NORTH);
        c.addKeyListener(new KeyAdapter() { // listener for player move, bullet firing
            boolean leftControl = true;  // for only one move input receive
            boolean rightControl = true; // for only one move input receive
            @Override
            public void keyPressed(KeyEvent e) {  // player move, shoot occur
                if(e.getKeyCode() == KeyEvent.VK_LEFT && leftControl && rightControl) {  // Only one movement input is received.
                    leftControl = false;
                    player.pSpeed = -5;  // direction is left.
                    th = new Thread(player);  // player move while hoding key
                    th.start();
                } else if(e.getKeyCode() == KeyEvent.VK_RIGHT && rightControl && leftControl) {  // Only one movement input is received.
                    rightControl = false;
                    player.pSpeed = 5;  // direction is right
                    th = new Thread(player);  // player move while hoding key
                    th.start();
                }
                if(e.getKeyCode() == KeyEvent.VK_SPACE) {  // shoot bullet
                    Bullet bul = new Bullet(new ImageIcon("images/bullet.png"));
                    bul.setSize(16,16);
                    bul.setLocation(player.getX()+c.getWidth()/2-10,player.getY());
                    c.add(bul);
                    c.repaint();
                }
            }
            @Override
            public void keyReleased(KeyEvent e) { // if keyReleased, ready to receive right or left move input
                if (e.getKeyCode() == KeyEvent.VK_LEFT || e.getKeyCode() == KeyEvent.VK_RIGHT) {   
                    th.interrupt();  // quit move thread.
                    leftControl = true;  // ready to receive move input
                    rightControl = true;  // readt to receive move input
                }
            }
        });
        setVisible(true);
        c.requestFocus();
    }
    class Enemy extends JLabel implements Runnable{ // enemyplane info
        int speed;
        public Enemy(ImageIcon enemyplane) {
            super(enemyplane);
            this.setSize(64,64);
            this.setVerticalAlignment(TOP);
            this.setHorizontalAlignment(LEFT);
            Thread th = new Thread(this);
            th.start();
        }

        @Override
        public void run() {  // enemy plane move on x-Axis not change y-Axis
            speed = -5;
            int homeX = this.getX();
            int homeY = this.getY();
            while (true) {
                this.setLocation(homeX + speed, homeY);
                if (homeX + speed > -60) {
                    speed -= 5;
                } else {
                    speed = 0;
                }
                homeX = c.getWidth(); // to fit in frame size
                try {
                    Thread.sleep(20);  // 20millsecond, move
                } catch (InterruptedException e) {
                    return;
                }
            }
        }
    }
    class Player extends JLabel implements Runnable { // player plane
        int pSpeed;
        public Player(ImageIcon controlPlane) {
            super(controlPlane);
            this.setSize(64,64);
            this.setVerticalAlignment(BOTTOM);
            this.setHorizontalAlignment(CENTER);
        }
        @Override
        public void run() { // player move thread
            int pXPosition = this.getX();
            int pYPosition = this.getY();
            while (true) {
                pXPosition += pSpeed;
                this.setLocation(pXPosition, pYPosition);
                if (pXPosition <= -c.getWidth()/2) { // Move within frame only
                    pXPosition = c.getWidth()/2;
                } else if (pXPosition > c.getWidth()/2) { // Move within frame only
                    pXPosition = -c.getWidth()/2;
                }
                try {
                    Thread.sleep(25);  // 25millsecond, move
                } catch (InterruptedException e) {
                    return;
                }
            }
        }
    }
    class Bullet extends JLabel implements Runnable {
        public Bullet(ImageIcon bullet) {
            super(bullet);
            Thread bulletthread = new Thread(this);
            bulletthread.start();
        }
        @Override
        public void run() {  // bullet is move to top from player.
            int bulXPosition = this.getX();
            int bulYPosition = this.getY();
            while(true) {
                bulYPosition -= 10;
                this.setLocation(bulXPosition,bulYPosition);
                if(bulYPosition <= enemy.getY() + 50 && bulYPosition >= enemy.getY()) {
                    if(bulXPosition <= enemy.getX() + 48 && bulXPosition >= enemy.getX()) {   // if enemy hit, bullet is removed and thread quit
                        enemy.speed = 200;
                        c.remove(this);
                        break;
                    }
                }
                if (bulYPosition < -16) { // if bullet is out of frame, bullet is removed
                    c.remove(this);
                    break;
                }
                try {
                    Thread.sleep(25);  // 25millsecond, move
                } catch (InterruptedException e) {
                    return;
                }
            }
        }
    }
    public static void main(String[] args) {
        new ShootingGame();
    }
}

Answer 1

Swing 不是线程安全的。这意味着您永远不应该从事件调度线程的上下文之外更新 UI。

解决方案是使用单个 Swing Timer 作为核心“主循环”，负责更新计划重绘的游戏状态。

一个更简单的整体解决方案是不以这种方式使用组件，而是使用一个可以绘制“实体”的容器并使用 Swing Timer 来更新这些“实体”的状态“定期进行。由于 paintComponent 和 Swing Timer 都在 EDT 内执行工作，因此可以安全地从(Timer)更新 UI，并防止可能的线程违规行为

首先查看 Concurrency in Swing和 How to use Swing Timers .

您还可以找到the key bindings API通常比 KeyListener 更可靠

您还可以查看something like this example更好地了解我刚才描述的内容