java - 为什么我的鱼不转身？

我在将鱼移到另一个地方并在到达右边缘或左边缘时调头时遇到麻烦。窗口是600 x400。在方法void swim();中，无论我如何更改，鱼都只会到达同一位置（鱼越过窗口右边缘）。我如何移动鱼，当它到达右边缘或左边缘并转身并移动到窗口的左边缘时？

注意：我正在使用GWindow，这是我学校提供的课程。

import java.awt.Color;
import java.util.Random;
import uwcse.graphics.*;

/**
 * A fish in a graphics window
 */

public class Fish {
    public static final int LEFT_MOVING = 0;
    public static final int RIGHT_MOVING = 0;

    // The graphics window the fish belongs to
    private GWindow window;

    // The location of the fish
    private int x;

    private int y;

    // Scale of the drawing of the fish
    private double scale;

    private Color color;

    private int direction;

    private Oval O1; Oval O2;
    private Triangle tail1; Triangle tail2;
    private Line eye1; Line eye2;

    /**
     * Draws a Fish in a graphics window
     *
     * @param x
     *            the x coordinate of the location of the fish
     * @param y
     *            the y coordinate of the location of the fish
     * @param scale
     *            the scale of the drawing of the fish
     * @param window
     *            the graphics window the fish belongs to
     */

    public Fish(int x, int y, double scale,int direction, GWindow window) {
        // Initialize the instance fields
        this.x  = x;
        this.y = y;
        this.scale = scale;
        this.window = window;
        this.color = randomColor();
        this.direction = direction;

        // Draw the fish
        this.draw();
    }
    private Color randomColor(){
        Random random = new Random();
        int R = random.nextInt(256);
        int G = random.nextInt(256);
        int B = random.nextInt(256);
        return new Color(R,B,G);
    }

    /**
     * Draws this fish
     */
    private void draw() {

        int Fsize = (int)(this.scale*15);

        this.O1 = new Oval(
                this.x - Fsize /3,
                this.y - Fsize /7 ,
                Fsize + 4*Fsize/3,
                Fsize  + Fsize/5,
                this.color,true);
        this.tail1 =new Triangle(
                this.x - Fsize,
                this.y,
                this.x - 2/Fsize,
                this.y + Fsize/2,
                this.x - Fsize,
                this.y + Fsize,this.color,true);
        this.eye1 = new Line(
                this.x + 15*Fsize/10,
                this.y + 5*Fsize/10  ,
                this.x + 15 *Fsize/10,
                this.y + 5* Fsize /10,
                Color.BLACK);
        Oval O2 = new Oval(
                this.x - 37*Fsize/5,
                this.y+ 27*Fsize/5 ,
                Fsize + 2*Fsize/3,
                Fsize  + Fsize/5,
                this.color,true);
        Line eye2 = new Line(
                this.x - 35*Fsize/5,
                this.y + 30*Fsize/5,
                this.x - 35*Fsize/5,
                this.y + 30*Fsize/5, Color.BLACK);
        Triangle tail2 =new Triangle(
                this.x - Fsize*5 ,
                this.y + 13*Fsize/2,
                this.x - 10*Fsize/2,
                this.y + 11*Fsize/2,
                this.x - Fsize*6,
                this.y + Fsize*6,this.color,true);
        this.window.add(O1);
        this.window.add(O2);
        this.window.add(tail2);
        this.window.add(tail1);
        this.window.add(eye1);
        this.window.add(eye2);
    }


    public void moveBy (int dx, int dy){
        x += dx;
        y += dy;
    }

    public void swim(){
        if (RIGHT_MOVING >= 250 || this.direction == RIGHT_MOVING){
            this.O1.moveBy(3,0);
            this.tail1.moveBy(3,0);
            this.eye1.moveBy(3,0);
        }
    }
}

最佳答案

您需要测试鱼与边界的碰撞，如果是，则更改动画设置以更改运动方向。这将需要在代码中移动鱼的位置使用一两个if块。在伪代码中，它看起来像：

if fish location is equal to or less than 0
   change deltaX to a positive value
if fish location + fish width is equal to or greater than width of tank
   change deltaX to a negative value

move fish by deltaX

我通常使用detlaX的绝对值，即

deltaX = Math.abs(deltaX);

和

deltaX = -Math.abs(deltaX);

而不是简单地交换标志。原因是，如果您只是交换标志，就可能会把鱼卡在拐角处。