Java: 在不影响已经发射的弹丸的情况下向不同方向发射弹丸

Question

所以基本上，当我改变方向时，我射出的弹丸会跟随。问题是之前所有的弹丸也都改变了方向

这是我的 projectile.java :

package dev.codenmore.tilegame.gfx;

import java.awt.Graphics;

import dev.codenmore.tilegame.Handler;
import dev.codenmore.tilegame.entity.creatures.Player;

public class Projectile {

    private double x;
    private double y;

    public Projectile (double x, double y, Handler handler){
        this.x = x;
        this.y = y;
    }

    public void tick(){
        if ( Player.getPos() == 3)
            x += 10;
        if ( Player.getPos() == 2)
            x -= 10;
        if (Player.getPos() == 1)
            y -= 10;
        if (Player.getPos() == 0)
            y += 10;
    }

    public void render(Graphics g){
        g.drawImage(Assets.arrow, (int) x, (int) y, null);
    }

}

这是我的controller.java：

package dev.codenmore.tilegame;

import java.awt.Graphics;
import java.util.LinkedList;

import dev.codenmore.tilegame.gfx.Projectile;

public class Controller {

    private static LinkedList<Projectile> b = new LinkedList <Projectile>();

    Projectile TempProjectile;

    Handler handler;

    public Controller(Handler handler){
        this.handler = handler;


    }

    public void tick(){
        for(int i = 0; i < b.size(); i++){
            TempProjectile = b.get(i);

            TempProjectile.tick();

        }
    }

    public void render(Graphics g){
        for(int i = 0; i < b.size(); i++){
            TempProjectile = b.get(i);

            TempProjectile.render(g);

        }

    }

    public static void addProjectile(Projectile block){
        b.add(block);
    }
    public static void removeProjectile(Projectile block){
        b.remove(block);
    }    
}

我的player.java：

package dev.codenmore.tilegame.entity.creatures;

import java.awt.Color;
import java.awt.Graphics;

import dev.codenmore.tilegame.Controller;
import dev.codenmore.tilegame.Game;
import dev.codenmore.tilegame.Handler;
import dev.codenmore.tilegame.gfx.Assets;
import dev.codenmore.tilegame.gfx.Projectile;

public class Player extends Creature {

    public static int pos = 0;



    public Player(Handler handler, float x, float y) {
        super(handler, x, y, Creature.DEFAULT_CREATURE_WIDTH, Creature.DEFAULT_CREATURE_HEIGHT);

        bounds.x = 46;
        bounds.y = 64;
        bounds.width = 32;
        bounds.height = 44;

    }

    @Override
    public void tick() {
        getInput();
        move();
        handler.getGameCamera().centerOnEntity(this);
    }

    private void getInput(){
        xMove = 0;
        yMove = 0;

        if(handler.getKeyManager().up)
            yMove = -speed;
        if(handler.getKeyManager().down)
            yMove = speed;
        if(handler.getKeyManager().left)
            xMove = -speed;
        if(handler.getKeyManager().right)
            xMove = speed;
        if(handler.getKeyManager().shoot)
            Controller.addProjectile(new Projectile((double)(x - handler.getGameCamera().getxOffset()),  (double)(y - handler.getGameCamera().getyOffset()), handler));

    }

    public static int getPos(){
        return pos;
    }

    @Override
    public void render(Graphics g) {



        if ( pos == 0)
            g.drawImage(Assets.player, (int)(x - handler.getGameCamera().getxOffset()), (int)(y - handler.getGameCamera().getyOffset()), width, height, null);
        if (pos == 1)
            g.drawImage(Assets.playerUp, (int)(x - handler.getGameCamera().getxOffset()), (int)(y - handler.getGameCamera().getyOffset()), width, height, null);
        if (pos == 2)
            g.drawImage(Assets.playerLeft, (int)(x - handler.getGameCamera().getxOffset()), (int)(y - handler.getGameCamera().getyOffset()), width, height, null);
        if (pos == 3)
            g.drawImage(Assets.playerRight, (int)(x - handler.getGameCamera().getxOffset()), (int)(y - handler.getGameCamera().getyOffset()), width, height, null);
        if(handler.getKeyManager().up){
            g.drawImage(Assets.playerUp, (int)(x - handler.getGameCamera().getxOffset()), (int)(y - handler.getGameCamera().getyOffset()), width, height, null);
            pos = 1;
        }else if(handler.getKeyManager().left){
            g.drawImage(Assets.playerLeft, (int)(x - handler.getGameCamera().getxOffset()), (int)(y - handler.getGameCamera().getyOffset()), width, height, null);
            pos = 2;
        }else if(handler.getKeyManager().right){
            g.drawImage(Assets.playerRight, (int)(x - handler.getGameCamera().getxOffset()), (int)(y - handler.getGameCamera().getyOffset()), width, height, null);
            pos = 3;
        }else if(handler.getKeyManager().down){
            g.drawImage(Assets.player, (int)(x - handler.getGameCamera().getxOffset()), (int)(y - handler.getGameCamera().getyOffset()), width, height, null);
            pos = 0;
        }

    }

}

我对编程还很陌生，对于这些错误我深表歉意。这是发生了什么：http://gyazo.com/118b525d22e42a92fece77f70201cdad

Answer 1

问题所在：

public void tick(){
    if ( Player.getPos() == 3)
        x += 10;
    if ( Player.getPos() == 2)
        x -= 10;
    if (Player.getPos() == 1)
        y -= 10;
    if (Player.getPos() == 0)
        y += 10;
}

在每个tick中询问玩家的方向，方向可以改变，因此射弹也会改变。为避免这种情况，请像这样在开始时保存每个弹丸的位置：

private int pos;
public Projectile (double x, double y, Handler handler){
    this.x = x;
    this.y = y;
    this.pos = Player.getPos();
}

然后打勾方法：

public void tick(){
    if ( pos == 3)
        x += 10;
    if ( pos == 2)
        x -= 10;
    if ( pos == 1)
        y -= 10;
    if ( pos == 0)
        y += 10;
}

切换会更好：

public void tick(){
    switch(pos){
        case 3: x+=10; break;
        case 2: x-=10; break;
        case 1: y-=10; break;
        case 0: y+=10; break;
    }
}

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