不能使用另一个 class 的方法？

Question

我知道还有其他线程具有类似的标题，但我已经完成了这些线程中建议的所有操作。

我正在尝试制作一款名为 Fossil Fuels 的恐龙赛车游戏，目前我正在制作一款通用游戏，其中的障碍物从顶部飘下来，需要避开。

我确实知道 Python，并且最近才开始学习 Java，所以这个问题听起来可能很愚蠢，但还是来吧。

import javax.swing.JFrame;
import javax.swing.ImageIcon;
import javax.swing.JLabel;

import java.lang.System;
import java.util.ArrayList;
import java.lang.Math;
public class MainLoop
{
    public static void main(String [] args)
    {
        boolean mloop = true;
        int obsMoveIncrease = 1;
        ArrayList obsList = new ArrayList();
        final String[] validObsTypes = {"tree", "rock", "bush"};
        long moveFrequency = 750;
        long beginningTime = System.currentTimeMillis();
        long obsInterval = 3000; //how often a new object is created in milliseconds
        long timeOfLastMove = System.currentTimeMillis();
        JFrame frame = new JFrame();
        ImageIcon background = new ImageIcon("background.jpg"); //background is 700 by 1500 px
        JLabel bgLabel = new JLabel(background);
        frame.add(bgLabel);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.pack();
        frame.setVisible(true);
        while (mloop)
        {
            int freshObsTypeNum = (int) Math.random() * 3;
            String freshObsType = validObsTypes[freshObsTypeNum]; //chooses a pseudo-random valid obstacle type
            if (System.currentTimeMillis() >= beginningTime + obsInterval) 
            { //checks if sufficient time has passed since last obstacle was created
                Obstacle obs = new Obstacle(freshObsType, 0);
                obsList.add(0, obs);
                beginningTime = System.currentTimeMillis(); //resets "clock"
            }


            if (System.currentTimeMillis() >= timeOfLastMove + moveFrequency) //checks if it is time to move obstacles
            {
                timeOfLastMove = System.currentTimeMillis();
                for (int i = 0; i < obsList.size(); i++)
                {
                    obsList.get(i).moveObs(obsMoveIncrease); //moves obstacles ERROR OCCURS ON moveObs
                    if (obsList.get(i).getObsY() > 1500)
                    {
                        obsList.remove(i);
                    }

                }
            }
        }
    }
}

这是我的障碍class:

import java.util.Arrays;
import javax.swing.ImageIcon;
import javax.swing.JLabel;
public class Obstacle
{
    private String obstacleType;
    private int obstacleXPos;
    public final int[] obsXlist = {0, 175, 350, 525}; //list of starting positions (4 slots along the x axis)
    int obstacleYPos = 0;
    public Obstacle(String type, int startPos)
    {
        obstacleType = type;
        obstacleXPos = obsXlist[startPos];
    }

    public int getObsX()
    {return obstacleXPos;}

    public int getObsY()
    {return obstacleYPos;}

    public void moveObs(int increase)
    {obstacleYPos += increase;}

    ImageIcon obstacleImg;
    public JLabel getObsImg() //gets image (on a label) for keyword given to constructor
    {
        if (obstacleType.equals("tree"))
            obstacleImg = new ImageIcon("treeObs.jpg");
        else if (obstacleType.equals("rock"))
            obstacleImg = new ImageIcon("rockObs.jpg");
        else if (obstacleType.equals("bush"))
            obstacleImg = new ImageIcon("bushObs.jpg");
        else
            System.out.println(obstacleType + " is not a valid obstacle type");

        JLabel obsLabel = new JLabel(obstacleImg);
        return obsLabel;
    }
}

它告诉我当我从 main 方法中调用 moveObs(int) 时找不到符号。我不知道为什么我无法访问 Obstacle class

中的 public 方法

Answer 1

obsList 没有类型。您正在尝试在 'Object' 上调用 moveObs()，而不是在 'Obstacle'.

上

要更改它，您需要使 obsList 成为这样的类型化列表：

ArrayList<Obstacle> obsList = new ArrayList<>();

不能使用另一个 class 的方法？

Can't use method from another class?

java

bluej