Java awt 为什么我只能删除链表中最近添加的内容

Question

我正在为我的大学计算机科学项目使用 Java awt 创建一个太空射击游戏。

我通过计时器每 3 秒生成一次敌人，并将其添加到 LinkedList 中，然后 for 循环 渲染它们。

在我的玩家子弹对象的类中，有 if 语句来检查激光是否进入敌人的范围，如果它们都为真，则会将敌人从敌人的范围中移除。 链接列表。

但是，仅删除 LinkedList 中最近添加的内容；子弹穿过其他子弹，但什么也没发生。这是我第一次制作游戏，也是我第一次使用LinkedList，所以请原谅任何误解。

Controller 类控制敌人，Laser类是子弹，Enemy类是Enemy对象。还有一个播放器、Main 和 GUI 类。

import java.awt.*;
import java.util.LinkedList;
import java.util.Timer;
import java.util.TimerTask;

public class Controller
{

private LinkedList<Enemy> e = new LinkedList<Enemy>();

Enemy tempEnemy, tempEnemy2
;
Main main;
int refreshSpawn = 3000;    //move timer refresh rate
int xpos;
int width;
int ypos;
int height;
Timer spawnTimer = new Timer();

public Controller(Main main)
{
    this.main = main;
    spawn();
}
public void spawn()
{
    spawnTimer.schedule(new TimerTask()
    {
        public void run()   //run method and timer
        {
            addEnemy(new Enemy(main, (int)(Math.random()*4+2)));
        }
    }, 0, refreshSpawn);
}
public void render(Graphics g)
{
    for(int i = 0; i < e.size(); i++)
    {
        tempEnemy = e.get(i);
        xpos = tempEnemy.getX();
        width = tempEnemy.getXsize();
        ypos = tempEnemy.getY();
        height = tempEnemy.getYsize();
        tempEnemy.render(g);
    }
}
public void update()
{
    for(int i = 0; i < e.size(); i++)
    {
        tempEnemy2 = e.get(i);
        tempEnemy2.move();
    }
}
public void addEnemy(Enemy enemy)
{
    e.add(enemy);
    System.out.println(e.size());
    //spawn();
}
public void removeEnemy()
{
    e.remove(tempEnemy);
}
public int getX()
{
    return xpos;
}
public int getY()
{
    return ypos;
}
public int getXsize()
{
    return width;
}
public int getYsize()
{
    return height;
}
public Enemy getEnemy()
{
    return tempEnemy;
}
}

import java.awt.*;

public class Enemy
{
Image ship; //image of enemy ship
int x, y;   //ship position
int speed;

public Enemy(Main main, int speed)  //constructing enemy
{
    this.speed = speed;
    ship = main.getImage(main.getDocumentBase(), "enemyShip"+(int)(Math.random()*6+1)+".png");  //picture for enemy ship
    x = (int)(Math.random()*900+1); //enemy has a starting position at a random x point
    y = -100;   //start ship slightly off screen so it doesn't suddenly appear
}
public void move()
{
    y += speed;
    if(y > 600)
    {
        y = -100;
        x = (int)(Math.random()*900);
    }
}
public void render(Graphics g)
{
    g.drawImage(ship, x, y, null);
}
public int getX()
{
    return x;
}
public int getY()
{
    return y;
}
public int getXsize()
{
    return ship.getWidth(null);
}
public int getYsize()
{
    return ship.getHeight(null);
}
}

import java.awt.*;

public class Laser
{
Image img;  //image of laser
int laserSpeed = 10;    //speed of laser
int x, y;   //position of laser
int xSize, ySize;   //size of laser
Controller cont;
GUI gui;
public Laser(Image img, int x, int y, Controller cont, GUI gui) //constructing laser
{
    this.cont = cont;
    this.img = img; //setting laser image
    this.gui = gui;
    xSize = x;  //size of laser
    ySize = y;  //size of laser
}
public void shoot(int x, int y, int shipSize)
{
    this.x = x + (shipSize/2) - (xSize/2);
    this.y = y;
}
public void move()
{
    y -= laserSpeed;
    if(x <= cont.getX() + cont.getXsize() && x + xSize >= cont.getX() - cont.getXsize())
    {
        if(y <= cont.getY() + cont.getYsize() && y > 0)
        {
            remove();
            cont.removeEnemy();
            gui.scoreUp(5);
        }
    }
}
public int getX()
{
    return x;
}
public int getY()
{
    return y;
}
public int getXSize()
{
    return xSize;
}
public int getYSize()
{
    return ySize;
}
public Image getImage()
{
    return img;
}
public void remove()
{
    y = -ySize;
    x = -100;
}
}

Answer 1

据我所知，tempEnemy 已通过 render 方法分配给 LinkedList 中的最后一个元素。这意味着当您调用 removeEnemy 时，它将删除最后渲染的对象(可能是您添加的最后一个对象)。

你应该做的是告诉Controller它应该使用哪个Enemy，它完全不知道你调用它时的意图是什么......