Java awt为什么我只能删除链表的最新添加

Question

I'm creating a space shooter game in Java awt for my college computer science project.

The enemies that I have spawn every 3 seconds via a timer and are added to a LinkedList , and a for loop renders them all.

In the class I have for my player's bullet object, there are if statements to check whether the laser comes into the bounds of an enemy, and if they are all true it removes the enemy from the LinkedList .

However, only the most recent addition to the LinkedList is being removed; the bullet passes through the others and nothing happens. This is my first time making a game, and the first time I've ever used a LinkedList , so excuse any misunderstandings.

The controller class controls the enemies, the Laser class is the bullet and the Enemy class is the Enemy object. There's also a player, Main and GUI class.

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

From what I can tell, tempEnemy is assigned to the last element in the LinkedList by the render method. This means that when you call removeEnemy it is removing the last rendered object (likely the last object you added).

What you should be doing is telling the Controller which Enemy it should be using, it has absolutely no idea what your intentions are when you call it...