Question

在我的populateArrayEnemy方法中，我用20个对象填充数组，最后将它们全部打印出来。
但是在我的paint和update方法中，enemyShip.size返回0。我哪里出错了？

更新：我的主要方法如下。

public class ActionEnemyShip {
EnemyShip es;

public ArrayList<EnemyShip> enemyShip = new ArrayList<EnemyShip>();

// Updating coordinates method //////////////

public void populateArrayEnemy(MainClass mc){
    int Min = 0, Max=800, result;

    for (int i =0; i <=20; i++){
             x = Min + (int)(Math.random() * ((Max - Min) + 1));
              y = 0 + (int)(Math.random() * ((600 - 0) + 1));
             EnemyShip es = new EnemyShip(x,y);

             enemyShip.add(es);

         }
    System.out.println(enemyShip);  
}

public void update(MainClass mc, Player p){ 

     for (int i = 0; i < enemyShip.size(); i++ ) {
         EnemyShip es = new EnemyShip();
         es = enemyShip.get(i);
         es.setX(es.getX()+ENEMY_SHIP_SPEED);
         enemyShip.set(i, es);
     }
}

// Paint method //////////////////////

public void paint(Graphics g, MainClass mc) {
    url = mc.getDocumentBase();
     enemyShipImg = mc.getImage(url, "craft.png");

     System.out.println("              paint  "+enemyShip.size());
        for (int i = 0; i < this.enemyShip.size(); i++){
            EnemyShip es = new EnemyShip();
             es = this.enemyShip.get(i);
             g.drawImage(enemyShipImg, es.getX(), es.getY(), mc);
        }

这是我的主要方法

 public void init()
{
    setSize(800, 600);
    es = new EnemyShip();
    as = new ActionEnemyShip();
    //as.populateArrayEnemy(mc);
}
public void start() {thread.start();}
public void destroy() {running = false;}
public void stop() {running = false;}
public void run() 

{
    while(running)
    {
        as.update(this, p); 

}

public void paint(Graphics g){

    as.paint(g, this);

}

Answer 1

 public void init()
{
    setSize(800, 600);
    es = new EnemyShip();
    as = new ActionEnemyShip();
    //as.populateArrayEnemy(mc); <== this is not happening
}

一般来说，这段代码写的很差，你应该考虑重构它。您的错误似乎是as.populateArrayEnemy(..)未被调用，因为它被注释掉了。

ArrayList大小返回0

1 个答案: