Java ClassNotFoundException（未知源）

所以，当我想运行新键入的代码时，我遵循了这一点，遇到了一个问题。我在logcat中得到了错误

ClassNotFound

    load: class guldbechnielsensolutions.MainActivity.class not found.
    java.lang.ClassNotFoundException: guldbechnielsensolutions.MainActivity.class
    at sun.applet.AppletClassLoader.findClass(Unknown Source)
    at java.lang.ClassLoader.loadClass(Unknown Source)
    at sun.applet.AppletClassLoader.loadClass(Unknown Source)
    at java.lang.ClassLoader.loadClass(Unknown Source)
    at sun.applet.AppletClassLoader.loadCode(Unknown Source)
    at sun.applet.AppletPanel.createApplet(Unknown Source)
    at sun.applet.AppletPanel.runLoader(Unknown Source)
    at sun.applet.AppletPanel.run(Unknown Source)
    at java.lang.Thread.run(Unknown Source)

每当我看到其他错误时，我总是得到一个故障所在的行号，但不在这里-为什么？（附问题）

自从上次成功运行以来，我只更改了两个类，因此我将发布这两个类：

主要活动：

package guldbechnielsensolutions;

import guldbechnielsensolutions.framework.Animation;
import java.applet.Applet;
import java.awt.Color;
import java.awt.Frame;
import java.awt.Graphics;
import java.awt.Image;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
import java.net.URL;
import java.util.ArrayList;

public class MainActivity extends Applet implements Runnable, KeyListener {
    private Sprite robot;
    private Heliboy hb, hb2;
    private Image image, currentSprite, character, character2, character3,
            characterDown, characterJumped, background, heliboy, heliboy2,
            heliboy3, heliboy4, heliboy5;

    public static Image tilegrassTop, tilegrassBot, tilegrassLeft, tilegrassRight, tiledirt;

    private Graphics second;
    private URL base;
    private static Background bg1, bg2;
    private Animation anim, hanim;

    private ArrayList<Tile> tilearray = new ArrayList<Tile>();

    @Override
    public void init() {

        setSize(800, 480);
        setBackground(Color.BLACK);
        setFocusable(true);
        addKeyListener(this);
        Frame frame = (Frame) this.getParent().getParent();
        frame.setTitle("Get Me Out! Alpha");
        try {
            base = getDocumentBase();
        } catch (Exception e) {
            // TODO: handle exception
        }

        // Image Setups
        character = getImage(base, "data/character.png");
        character2 = getImage(base, "data/character2.png");
        character3 = getImage(base, "data/character3.png");

        characterDown = getImage(base, "data/down.png");
        characterJumped = getImage(base, "data/jumped.png");

        heliboy = getImage(base, "data/heliboy.png");
        heliboy2 = getImage(base, "data/heliboy2.png");
        heliboy3 = getImage(base, "data/heliboy3.png");
        heliboy4 = getImage(base, "data/heliboy4.png");
        heliboy5 = getImage(base, "data/heliboy5.png");

        background = getImage(base, "data/background.png");

        tiledirt = getImage(base, "data/tiledirt.png");
        tilegrassTop = getImage(base, "data/tilegrasstop.png");
        tilegrassBot = getImage(base, "data/tilegrassbot.png");
        tilegrassLeft = getImage(base, "data/tilegrassleft.png");
        tilegrassRight = getImage(base, "data/tilegrassright.png");


        anim = new Animation();
        anim.addFrame(character, 1250);
        anim.addFrame(character2, 50);
        anim.addFrame(character3, 50);
        anim.addFrame(character2, 50);

        hanim = new Animation();
        hanim.addFrame(heliboy, 100);
        hanim.addFrame(heliboy2, 100);
        hanim.addFrame(heliboy3, 100);
        hanim.addFrame(heliboy4, 100);
        hanim.addFrame(heliboy5, 100);
        hanim.addFrame(heliboy4, 100);
        hanim.addFrame(heliboy3, 100);
        hanim.addFrame(heliboy2, 100);

        currentSprite = anim.getImage();
    }

    @Override
    public void start() {
        bg1 = new Background(0, 0);
        bg2 = new Background(2160, 0);

        // Initialize Tiles
        try {
            loadMap("data/map1.txt");
        } catch (IOException e) {
            System.out.println("LOL");
            e.printStackTrace();
            System.out.println("LOL");
        }

        hb = new Heliboy(340, 360);
        hb2 = new Heliboy(700, 360);
        robot = new Sprite();

        Thread thread = new Thread(this);
        thread.start();
    }

    private void loadMap(String filename) throws IOException {
        ArrayList lines = new ArrayList();
        int width = 0;
        int height = 0;

        BufferedReader reader = new BufferedReader(new FileReader(filename));
        while (true) {
            String line = reader.readLine();
            // no more lines to read
            if (line == null) {
                reader.close();
                break;
            }

            if (!line.startsWith("!")) {
                lines.add(line);
                width = Math.max(width, line.length());

            }
        }
        height = lines.size();

        for (int j = 0; j < 12; j++) {
            String line = (String) lines.get(j);
            for (int i = 0; i < width; i++) {

                if (i < line.length()) {
                    char ch = line.charAt(i);
                    Tile t = new Tile(i, j, Character.getNumericValue(ch));
                    tilearray.add(t);
                }

            }
        }

    }

    @Override
    public void stop() {
        // TODO Auto-generated method stub
    }

    @Override
    public void destroy() {
        // TODO Auto-generated method stub
    }

    @Override
    public void run() {
        while (true) {
            robot.update();
            if (robot.isJumped()) {
                currentSprite = characterJumped;
            } else if (robot.isJumped() == false && robot.isDucked() == false) {
                currentSprite = anim.getImage();
            }

            ArrayList projectiles = robot.getProjectiles();
            for (int i = 0; i < projectiles.size(); i++) {
                Projectile p = (Projectile) projectiles.get(i);
                if (p.isVisible() == true) {
                    p.update();
                } else {
                    projectiles.remove(i);
                }
            }

            updateTiles();
            hb.update();
            hb2.update();
            bg1.update();
            bg2.update();
            animate();
            repaint();
            try {
                Thread.sleep(17);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }

    public void animate() {
        anim.update(10);
        hanim.update(50);
    }

    @Override
    public void update(Graphics g) {
        if (image == null) {
            image = createImage(this.getWidth(), this.getHeight());
            second = image.getGraphics();
        }

        second.setColor(getBackground());
        second.fillRect(0, 0, getWidth(), getHeight());
        second.setColor(getForeground());
        paint(second);

        g.drawImage(image, 0, 0, this);

    }

    @Override
    public void paint(Graphics g) {
        g.drawImage(background, bg1.getBgX(), bg1.getBgY(), this);
        g.drawImage(background, bg2.getBgX(), bg2.getBgY(), this);
        paintTiles(g);

        ArrayList projectiles = robot.getProjectiles();
        for (int i = 0; i < projectiles.size(); i++) {
            Projectile p = (Projectile) projectiles.get(i);
            g.setColor(Color.YELLOW);
            g.fillRect(p.getX(), p.getY(), 10, 5);
        }

        g.drawImage(currentSprite, robot.getCenterX() - 61,
                robot.getCenterY() - 63, this);
        g.drawImage(hanim.getImage(), hb.getCenterX() - 48,
                hb.getCenterY() - 48, this);
        g.drawImage(hanim.getImage(), hb2.getCenterX() - 48,
                hb2.getCenterY() - 48, this);
    }

    private void updateTiles() {

        for (int i = 0; i < tilearray.size(); i++) {
            Tile t = (Tile) tilearray.get(i);
            t.update();
        }

    }

    private void paintTiles(Graphics g) {
        for (int i = 0; i < tilearray.size(); i++) {
            Tile t = (Tile) tilearray.get(i);
            g.drawImage(t.getTileImage(), t.getTileX(), t.getTileY(), this);
        }
    }

    @Override
    public void keyPressed(KeyEvent e) {

        switch (e.getKeyCode()) {
        case KeyEvent.VK_UP:
            System.out.println("Move up");
            break;

        case KeyEvent.VK_DOWN:
            currentSprite = characterDown;
            if (robot.isJumped() == false) {
                robot.setDucked(true);
                robot.setSpeedX(0);
            }
            break;

        case KeyEvent.VK_LEFT:
            robot.moveLeft();
            robot.setMovingLeft(true);
            break;

        case KeyEvent.VK_RIGHT:
            robot.moveRight();
            robot.setMovingRight(true);
            break;

        case KeyEvent.VK_SPACE:
            robot.jump();
            break;

        case KeyEvent.VK_CONTROL:
            if (robot.isDucked() == false && robot.isJumped() == false) {
                robot.shoot();
            }
            break;

        }

    }

    @Override
    public void keyReleased(KeyEvent e) {
        switch (e.getKeyCode()) {
        case KeyEvent.VK_UP:
            System.out.println("Stop moving up");
            break;

        case KeyEvent.VK_DOWN:
            currentSprite = anim.getImage();
            robot.setDucked(false);
            break;

        case KeyEvent.VK_LEFT:
            robot.stopLeft();
            break;

        case KeyEvent.VK_RIGHT:
            robot.stopRight();
            break;

        case KeyEvent.VK_SPACE:
            break;

        }

    }

    @Override
    public void keyTyped(KeyEvent e) {
        // TODO Auto-generated method stub

    }

    public static Background getBg1() {
        return bg1;
    }

    public static Background getBg2() {
        return bg2;
    }

}

为什么我找不到一个类？我没有举例说明任何新的类（除了以前工作良好的sprite…）

---

编辑：

更改这些行后：

        if (type == 5) {
            tileImage = MainActivity.tiledirt;
        } else if (type == 8) {
            tileImage = MainActivity.tilegrassTop;
        } else if (type == 4) {
            tileImage = MainActivity.tilegrassLeft;
        } else if (type == 6) {
            tileImage = MainActivity.tilegrassRight;
        } else if (type == 2) {
            tileImage = MainActivity.tilegrassBot;
        }

在Tile.java中 MainActivity.java中有以下内容：

tiledirt = getImage(base, "data/tiledirt.png");
tilegrassTop = getImage(base, "data/tilegrasstop.png");
tilegrassBot = getImage(base, "data/tilegrassbot.png");
tilegrassLeft = getImage(base, "data/tilegrassleft.png");
tilegrassRight = getImage(base, "data/tilegrassright.png");

错误来了。现在，如果我使用CTRL+Z返回“runnable”代码，它会抛出相同的错误

---

Edit2:

当我运行代码时，它可以正常工作，但会抛出错误并生成此窗口：

---

在此之前，它由背景和精灵填充。

因此，在尝试调试时，我找到了一个可以尝试的答案。我做到了：

右键单击项目>生成路径>配置生成路径

---

在那里，我可以添加和删除导致问题的文件夹。现在我的代码运行得很好。

您是如何构建应用程序的？你添加了必要的依赖项了吗？我相信是的，我运行了代码，工作得很好，修改了几行，然后砰的一声，这个错误就出现了。我将编辑我更改的行。您的MainActivity类可能存在编译错误。您是否能够在更改后编译MainActivity？我也能够运行它。但是什么也没发生，只是出现了一个空的小程序窗口。您是如何加载小程序的？编译完成后，需要将它们放在applet可以找到类的地方

tiledirt = getImage(base, "data/tiledirt.png");
tilegrassTop = getImage(base, "data/tilegrasstop.png");
tilegrassBot = getImage(base, "data/tilegrassbot.png");
tilegrassLeft = getImage(base, "data/tilegrassleft.png");
tilegrassRight = getImage(base, "data/tilegrassright.png");