java - 如何为每个云提供单独的 x 位置，以便我可以根据该位置绘制它

Question

所以基本上我有一个风景项目，我根据 Cloud 类中的构造函数创建了一个“云”列表。每次我创建这些云的列表时，我都会为 x 生成一个随机数。当我绘制云时，它具有 x 值。在动画中，我添加了云的 x 轴，并且希望每次单个云的 x 轴超过 800 时，它们都会变为 -150。我以为我做对了，但由于某种原因，云移动得非常快:(

import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.ThreadLocalRandom;
import javax.swing.JButton;
import javax.swing.JPanel;

public class Scenery extends JPanel implements ActionListener {

    private RainSnowDrop[] rain, snow;

    private Cloud[] cloud;

    private double cloudX;

    private Background background;

    private Tree[] tree;

    private Mountain mountain;

    private JButton fallB, winterB, springB, summerB;

    private boolean fall, winter, spring, summer;

    private Color skyColor, grassColor, treeColor, treeStickColor, mountainColor;

    int[] getXs = new int[7];


    public Scenery() {

        setLayout(null);

        fallB = new JButton("Fall");
        fallB.setBounds(50, 475, 80, 40);
        fallB.addActionListener(this);
        add(fallB);

        winterB = new JButton("Winter");
        winterB.setBounds(250, 475, 80, 40);
        winterB.addActionListener(this);
        add(winterB);

        springB = new JButton("Spring");
        springB.setBounds(450, 475, 80, 40);
        springB.addActionListener(this);
        add(springB);

        summerB = new JButton("Summer");
        summerB.setBounds(650, 475, 80, 40);
        summerB.addActionListener(this);
        add(summerB);

        skyColor = (Color.WHITE);
        grassColor = (Color.WHITE);
        treeColor = (Color.WHITE);
        treeStickColor = (Color.WHITE);
        mountainColor = (Color.WHITE);

        snow = new RainSnowDrop[200];
        rain = new RainSnowDrop[200];
        tree = new Tree[5];
        cloud = new Cloud[7];
        background = new Background();
        mountain = new Mountain();

        for (int i = 0; i < rain.length; i++) {
            rain[i] = new RainSnowDrop();
        }
        for (int i = 0; i < snow.length; i++) {
            snow[i] = new RainSnowDrop();
        }
        for (int i = 0; i < tree.length; i++) {
            tree[i] = new Tree();
        }
        for (int i = 0; i < cloud.length; i++) {
            cloud[i] = new Cloud();
            getXs[i] = Cloud.xs.get(i);
        }

        setFocusable(true);
    }

    public Dimension getPreferredSize() {

        return new Dimension(800, 600);

    }

    public void paintComponent(Graphics g) {

        super.paintComponents(g);

        background.drawBackground(g, grassColor, skyColor);

        mountain.drawMountain(g, mountainColor, Color.WHITE, winter);

        for (int i = 0; i < tree.length; i++) {
            tree[i].drawTree(g, treeColor, treeStickColor, winter);
        }

        if (spring) {

            mountainColor = new Color(68, 73, 68);
            treeStickColor = new Color(179, 23, 23);
            treeColor = (Color.GREEN);
            grassColor = new Color(120, 225, 120);
            skyColor = new Color(198, 245, 242);

            for (int i = 0; i < rain.length; i++) {
                rain[i].drawRain(g);
            }
        }

        if (winter) {

            mountainColor = new Color(68, 73, 68);
            treeStickColor = new Color(179, 23, 23);
            treeColor = new Color(210, 210, 210);
            skyColor = (Color.LIGHT_GRAY);
            grassColor = new Color(190, 228, 200);

            for (int i = 0; i < cloud.length; i++) {
                cloud[i].drawCloud(g, getXs[i] + cloudX);
            }

            for (int i = 0; i < snow.length; i++) {
                snow[i].drawSnow(g);
            }
        }

        //Summer

        //Fall
    }

    public void animate() {

        while (true) {

            for (int i = 0; i < cloud.length; i++) {
                System.out.println(getXs[i]);
            }

            try {
                Thread.sleep(5); //in milliseconds
            }
            catch(InterruptedException ex) {
                Thread.currentThread().interrupt();
            }

            cloudX += 0.2;

            for (int i = 0; i < cloud.length; i++) {
                getXs[i] += (int) cloudX;
                if (getXs[i] > 800) getXs[i] = -150;
            }

            if (spring) {
                for (int i = 0; i < rain.length; i++) {
                    rain[i].moveDownRain();
                }
            }
            else if (winter) {
                for (int i = 0; i < snow.length; i++) {
                    snow[i].moveDownSnow();
                }
            }
            repaint();
        }
    }

    public void actionPerformed(ActionEvent e) {

        if (e.getSource() == fallB) {
            fall = true;
            spring = false;
            winter = false;
            summer = false;
        }
        else if (e.getSource() == winterB) {
            winter = true;
            spring = false;
            summer = false;
            fall = false;
        }
        else if (e.getSource() == springB) {
            spring = true;
            winter = false;
            fall = false;
            summer = false;
        }
        else if (e.getSource() == summerB) {
            summer = true;
            spring = false;
            winter = false;
            fall = false;
        }
    }
}

这是Cloud类:

import java.awt.Color;
import java.awt.Graphics;
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.ThreadLocalRandom;

public class Cloud {

    private Color cloudColor;

    public static List<Integer> xs = new ArrayList<Integer>();

    private int x, y;

    private int x1 = 25, x2 = 65, x3 = 106;

    public Cloud () {

        cloudColor = new Color(128, 128, 128);

        x = ThreadLocalRandom.current().nextInt(50, 790);

        y = ThreadLocalRandom.current().nextInt(1, 100);

        xs.add(x);

    }

    public void drawCloud(Graphics g, double x) {

        g.setColor(cloudColor);

        g.fillOval((int) x + x1 + this.x, 25 + y, 70, 58);
        g.fillOval((int) x + x2 + this.x, 15 + y, 70, 58);  
        g.fillOval((int) x + x2 + this.x, 50 + y, 70, 58);
        g.fillOval((int) x + x3 + this.x, 33 + y, 70, 58);

    }
}

Answer 1

but for some reason the clouds are moving really fast

不太确定问题是什么，只是关于代码的一些一般注释:

Thread.sleep(5); //in milliseconds

sleep 5 毫秒意味着刷新率为 200，这太高了。另外，我不认为 Java 时钟那么精确，无法让您在这么小的时间片内 sleep 。人们倾向于选择 60 帧，大约为 16 毫秒。

cloudX += 0.2;

然后将移动量增加 0.2，这意味着云无论如何都会在循环中每 5 次移动一次。那么为什么要进行所有额外的处理呢？只需将 x 值增加 1 并将 sleep 时间更改为 25 毫秒即可。

public static List<Integer> xs = new ArrayList<Integer>();

您不应该使用静态变量。云的属性应该是实例变量。也就是说，云对象应该是自包含的，因此它具有绘制自身所需的所有信息。

所以你需要一个像locationX这样的变量。

for (int i = 0; i < cloud.length; i++) {
    getXs[i] += (int) cloudX;
    if (getXs[i] > 800) getXs[i] = -150;
}

经过上述建议后，您可以删除“getXs”变量。相反，您可以为 Cloud 类创建一个类似 move(int Pixels) 的方法。 move(...) 方法只是将 locationX 变量更新为其新值。

然后，drawCloud(...) 方法将更改为仅需要 Graphics 对象。绘画将更改为使用 locationX 变量。

public static List<Integer> xs = new ArrayList<Integer>();

我猜问题出在静态变量上。这意味着每个 Cloud 对象都使用相同的变量。因此，每次增加每个云的值时，也会增加所有云的值。 “x 位置”应该位于实例变量中。

    snow = new RainSnowDrop[200];
    rain = new RainSnowDrop[200];
    tree = new Tree[5];
    cloud = new Cloud[7];

不要使用数组。而是使用 ArrayList。这将允许您的代码不受限制地动态添加对象。

while (true) {

不要使用无限循环。动画是通过使用 Swing Timer 来完成的。阅读 Swing 教程中关于 How to Use Timers 的部分了解更多信息。

查看:get width and height of JPanel outside of the class一个实现上述所有建议的示例。请注意“Ball”类如何具有绘制球所需的所有属性。这允许您将其行为自定义为不同的颜色和 Action 。