java - 如果定义了一个带参数的构造函数，为什么我的代码不使用默认的非参数化构造函数？

Question

好的，我有我的主类，它从我的框架中加载所有内容。我现在遇到的麻烦是我的碰撞检测；我明白了，所以如果它撞到什么东西，就会发生什么事。我有一个在 GameScreen 类中调用 GameOverUI 的方法，但我想在我的 Enemy.class 中使用它。我为该对象创建了一个新实例，但它说它未定义。我没有得到的是该类没有定义，但名为 GameScreen 的方法由 (Game game) 定义。

import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;

import android.graphics.Color;
import android.graphics.Paint;

import com.vaughanslater.framework.Game;
import com.vaughanslater.framework.Graphics;
import com.vaughanslater.framework.Image;
import com.vaughanslater.framework.Input.TouchEvent;
import com.vaughanslater.framework.Screen;

public class GameScreen extends Screen {
    enum GameState { 
        Ready, Running, Paused, GameOver
    }

    GameState state = GameState.Ready;

    // Variable Setup

    private static Background bg1, bg2;
    private static Robot robot;
    public static Heliboy hb, hb2;

    private Image currentSprite, character, character2, character3, heliboy,
            heliboy2, heliboy3, heliboy4, heliboy5;
    private Animation anim, hanim;

    private ArrayList tilearray = new ArrayList();

    int livesLeft = 1;
    Paint paint, paint2;

    public GameScreen(Game game) {
        super(game);

        // Initialize game objects here

        bg1 = new Background(0, 0);
        bg2 = new Background(2160, 0);
        robot = new Robot();
        hb = new Heliboy(340, 360);
        hb2 = new Heliboy(700, 360);

        character = Assets.character;
        character2 = Assets.character2;
        character3 = Assets.character3;

        heliboy = Assets.heliboy;
        heliboy2 = Assets.heliboy2;
        heliboy3 = Assets.heliboy3;
        heliboy4 = Assets.heliboy4;
        heliboy5 = Assets.heliboy5;

        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();

        loadMap();

        // Defining a paint object
        paint = new Paint();
        paint.setTextSize(30);
        paint.setTextAlign(Paint.Align.CENTER);
        paint.setAntiAlias(true);
        paint.setColor(Color.WHITE);

        paint2 = new Paint();
        paint2.setTextSize(100);
        paint2.setTextAlign(Paint.Align.CENTER);
        paint2.setAntiAlias(true);
        paint2.setColor(Color.WHITE);

    }

    private void loadMap() {
        ArrayList lines = new ArrayList();
        int width = 0;
        int height = 0;

        Scanner scanner = new Scanner(SampleGame.map);
        while (scanner.hasNextLine()) {
            String line = scanner.nextLine();

            // no more lines to read
            if (line == null) {
                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 update(float deltaTime) {

        List touchEvents = game.getInput().getTouchEvents();

        // We have four separate update methods in this example.
        // Depending on the state of the game, we call different update methods.
        // Refer to Unit 3's code. We did a similar thing without separating the
        // update methods.

        if (state == GameState.Ready)
            updateReady(touchEvents);
        if (state == GameState.Running)
            updateRunning(touchEvents, deltaTime);
        if (state == GameState.Paused)
            updatePaused(touchEvents);
        if (state == GameState.GameOver)
            updateGameOver(touchEvents);
    }

    private void updateReady(List touchEvents) {

        // This example starts with a "Ready" screen.
        // When the user touches the screen, the game begins.
        // state now becomes GameState.Running.
        // Now the updateRunning() method will be called!

        if (touchEvents.size() > 0)
            state = GameState.Running;
    }

    private void updateRunning(List touchEvents, float deltaTime) {

        // This is identical to the update() method from our Unit 2/3 game.

        // 1. All touch input is handled here:
        int len = touchEvents.size();
        for (int i = 0; i < len; i++) {
            TouchEvent event = (TouchEvent) touchEvents.get(i);
            if (event.type == TouchEvent.TOUCH_DOWN) {

                if (event.x > 400) {
                    robot.jump();
                    currentSprite = anim.getImage();
                    robot.setDucked(false);
                }

                else if (inBounds(event, 0, 350, 65, 65)) {

                    if (robot.isDucked() == false && robot.isJumped() == false
                            && robot.isReadyToFire()) {
                        robot.shoot();
                    }
                }

                else if (event.x < 400
                        && robot.isJumped() == false) {
                    currentSprite = Assets.characterDown;
                    robot.setDucked(true);
                    robot.setSpeedX(0);

                }

                //if (event.x > 400) {
                // Move right.
                //  robot.moveRight();
                //  robot.setMovingRight(true);
                //}

            }

            if (event.type == TouchEvent.TOUCH_UP) {

                if (event.x < 400) {
                    currentSprite = anim.getImage();
                    robot.setDucked(false);

                }

                if (inBounds(event, 0, 0, 35, 35)) {
                    pause();

                }

                if (event.x > 400) {
                    // Move right.
                    robot.stopRight();
                }
            }

        }

        // 2. Check miscellaneous events like death:

        if (livesLeft == 0) {
            state = GameState.GameOver;
        }

        // 3. Call individual update() methods here.
        // This is where all the game updates happen.
        // For example, robot.update();
        robot.update();
        if (robot.isJumped()) {
            currentSprite = Assets.characterJump;
        } 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();

        if (robot.getCenterY() > 500) {
            state = GameState.GameOver;
        }
    }

    private boolean inBounds(TouchEvent event, int x, int y, int width,
            int height) {
        if (event.x > x && event.x < x + width - 1 && event.y > y
                && event.y < y + height - 1)
            return true;
        else
            return false;
    }

    private void updatePaused(List touchEvents) {
        int len = touchEvents.size();
        for (int i = 0; i < len; i++) {
            TouchEvent event = (TouchEvent) touchEvents.get(i);
            if (event.type == TouchEvent.TOUCH_UP) {
                if (inBounds(event, 0, 0, 800, 240)) {

                    if (!inBounds(event, 0, 0, 35, 35)) {
                        resume();
                    }
                }

                if (inBounds(event, 0, 240, 800, 240)) {
                    nullify();
                    goToMenu();
                }
            }
        }
    }

    private void updateGameOver(List touchEvents) {
        int len = touchEvents.size();
        for (int i = 0; i < len; i++) {
            TouchEvent event = (TouchEvent) touchEvents.get(i);
            if (event.type == TouchEvent.TOUCH_DOWN) {
                if (inBounds(event, 0, 0, 800, 480)) {
                    nullify();
                    game.setScreen(new MainMenuScreen(game));
                    return;
                }
            }
        }

    }

    private void updateTiles() {

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

    }

    @Override
    public void paint(float deltaTime) {
        Graphics g = game.getGraphics();

        g.drawImage(Assets.background, bg1.getBgX(), bg1.getBgY());
        g.drawImage(Assets.background, bg2.getBgX(), bg2.getBgY());
        paintTiles(g);

        ArrayList projectiles = robot.getProjectiles();
        for (int i = 0; i < projectiles.size(); i++) {
            Projectile p = (Projectile) projectiles.get(i);
            g.drawRect(p.getX(), p.getY(), 10, 5, Color.YELLOW);
        }
        // First draw the game elements.

        g.drawImage(currentSprite, robot.getCenterX() - -15,
                robot.getCenterY() - -17);
        g.drawImage(hanim.getImage(), hb.getCenterX() - 48,
                hb.getCenterY() - 48);
        g.drawImage(hanim.getImage(), hb2.getCenterX() - 48,
                hb2.getCenterY() - 48);

        // Example:
        // g.drawImage(Assets.background, 0, 0);
        // g.drawImage(Assets.character, characterX, characterY);

        // Secondly, draw the UI above the game elements.
        if (state == GameState.Ready)
            drawReadyUI();
        if (state == GameState.Running)
            drawRunningUI();
        if (state == GameState.Paused)
            drawPausedUI();
        if (state == GameState.GameOver)
            drawGameOverUI();

    }

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

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

    private void nullify() {

        // Set all variables to null. You will be recreating them in the
        // constructor.
        paint = null;
        bg1 = null;
        bg2 = null;
        robot = null;
        hb = null;
        hb2 = null;
        currentSprite = null;
        character = null;
        character2 = null;
        character3 = null;
        heliboy = null;
        heliboy2 = null;
        heliboy3 = null;
        heliboy4 = null;
        heliboy5 = null;
        anim = null;
        hanim = null;

        // Call garbage collector to clean up memory.
        System.gc();

    }

    private void drawReadyUI() {
        Graphics g = game.getGraphics();

        g.drawARGB(155, 0, 0, 0);
        g.drawString("Tap to Start.", 400, 240, paint);

    }

    private void drawRunningUI() {
        Graphics g = game.getGraphics();
        //g.drawImage(Assets.button, 0, 285, 0, 0, 65, 65);
        //g.drawImage(Assets.button, 0, 350, 0, 65, 65, 65);
        //g.drawImage(Assets.button, 0, 415, 0, 130, 65, 65);
        g.drawImage(Assets.button, 0, 0, 0, 195, 35, 35);

    }

    private void drawPausedUI() {
        Graphics g = game.getGraphics();
        // Darken the entire screen so you can display the Paused screen.
        g.drawARGB(155, 0, 0, 0);
        g.drawString("Resume", 400, 165, paint2);
        g.drawString("Menu", 400, 360, paint2);

    }

    public void drawGameOverUI() {
        Graphics g = game.getGraphics();
        g.drawRect(0, 0, 1281, 801, Color.BLACK);
        g.drawString("GAME OVER.", 400, 240, paint2);
        g.drawString("Tap to return.", 400, 290, paint);

    }

    @Override
    public void pause() {
        if (state == GameState.Running)
            state = GameState.Paused;

    }

    @Override
    public void resume() {
        if (state == GameState.Paused)
            state = GameState.Running;
    }

    public GameState getState() {
        return state;
    }

    public void setState(GameState state) {
        this.state = state;
    }

    @Override
    public void dispose() {

    }

    @Override
    public void backButton() {
        pause();
    }

    private void goToMenu() {
        // TODO Auto-generated method stub
        game.setScreen(new MainMenuScreen(game));

    }

    public static Background getBg1() {
        // TODO Auto-generated method stub
        return bg1;
    }

    public static Background getBg2() {
        // TODO Auto-generated method stub
        return bg2;
    }

    public static Robot getRobot() {
        // TODO Auto-generated method stub
        return robot;
    }


}

这也是我的敌人类:

import android.graphics.Rect;

public class Enemy {

    private int power, centerX, speedX, centerY;
    private Background bg = GameScreen.getBg1();
    private Robot robot = GameScreen.getRobot();
    public Rect r = new Rect(0, 0, 0, 0);
    public int health = 5;
    private int movementSpeed;

    // Behavioural Methods
    public void update() {
        follow();
        centerX += speedX;
        speedX = bg.getSpeedX() * 5 + movementSpeed;
        r.set(centerX - 25, centerY - 25, centerX + 25, centerY + 35);

        if (Rect.intersects(r, Robot.yellowRed)) {
            checkCollision();
        }

    }
private void checkCollision() {
    if (Rect.intersects(r, Robot.rect) || Rect.intersects(r, Robot.rect2)
            || Rect.intersects(r, Robot.rect3)
            || Rect.intersects(r, Robot.rect4)) {
        GameScreen state = new GameScreen(); // This is where it errors
    }
}

public void follow() {

    if (centerX < -95 || centerX > 810) {
        movementSpeed = 0;
    }

    else if (Math.abs(robot.getCenterX() - centerX) < 5) {
        movementSpeed = 0;
    }

    else {

        if (robot.getCenterX() >= centerX) {
            movementSpeed = 1;
        } else {
            movementSpeed = -1;
        }
    }

}

public void die() {

}

public void attack() {

}

public int getPower() {
    return power;
}

public int getSpeedX() {
    return speedX;
}

public int getCenterX() {
    return centerX;
}

public int getCenterY() {
    return centerY;
}

public Background getBg() {
    return bg;
}

public void setPower(int power) {
    this.power = power;
}

public void setSpeedX(int speedX) {
    this.speedX = speedX;
}

public void setCenterX(int centerX) {
    this.centerX = centerX;
}

public void setCenterY(int centerY) {
    this.centerY = centerY;
}

public void setBg(Background bg) {
    this.bg = bg;
}

所以这是错误的地方:

GameScreen state = new GameScreen(); // This is where it errors

我不明白，我不是在调用已定义的方法 GameScreen(Game game)，而是在调用未定义的类。我想使用 drawGameOverUI();。

抱歉代码墙..至少你可以看到一切。

Answer 1

如果您定义任何构造函数，则永远不会使用默认构造函数。请定义 GameScreen() 的实现或删除 GameScreen(Game game) 的实现。

像这样定义一个默认构造函数-

  public GameScreen() {
        super();

        // Initialize game objects here

        bg1 = new Background(0, 0);
        bg2 = new Background(2160, 0);
        robot = new Robot();
        hb = new Heliboy(340, 360);
        hb2 = new Heliboy(700, 360);

        character = Assets.character;
        character2 = Assets.character2;
        character3 = Assets.character3;

        heliboy = Assets.heliboy;
        heliboy2 = Assets.heliboy2;
        heliboy3 = Assets.heliboy3;
        heliboy4 = Assets.heliboy4;
        heliboy5 = Assets.heliboy5;

        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();

        loadMap();

        // Defining a paint object
        paint = new Paint();
        paint.setTextSize(30);
        paint.setTextAlign(Paint.Align.CENTER);
        paint.setAntiAlias(true);
        paint.setColor(Color.WHITE);

        paint2 = new Paint();
        paint2.setTextSize(100);
        paint2.setTextAlign(Paint.Align.CENTER);
        paint2.setAntiAlias(true);
        paint2.setColor(Color.WHITE);

    }