Question

我正在尝试制作一个生成25个随机椭圆的程序，然后画一个球并让它反弹，我做了一些，我生成了椭圆形，我让球移动但是当我添加线程时它不断重复绘制椭圆形循环，我有点为什么会发生这种情况，但我不知道如何解决它。

基本上我的程序应该：

在边框内的随机位置绘制25个随机大小的椭圆 - 已完成
画一个球然后移动 - 完成
让球反弹 - 没有完成，但我知道该怎么做

但它不断重复第一步。

这是我写的代码，哦，我现在必须使用applet它的部分课程请不要建议我使用swing或其他东西：

import java.applet.Applet;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Image;

public class As4B extends Applet implements Runnable 
{

    public int x, y;
    public int width = 854;
    public int height = 480;
    public int border = 20;
    public Image offscreen;
    public Graphics d;


    public void init()
    {
        setSize(width,height);
        Thread th = new Thread(this);
        th.start();
        offscreen = createImage(width,height);
        d = offscreen.getGraphics();
    }

    public void run() 
    {
        x = 100;
        y = 100;
        while(true)
        {
            x ++;
            y ++;
            repaint();
            try {
                Thread.sleep(50);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }

    }
    public void paint(Graphics gfx)
    {
        d.setColor(java.awt.Color.black);
        d.fillRect(0, 0, width, height);
        d.setColor(java.awt.Color.green);
        d.fillRect(0 + border, 0 + border, (width - (border * 2)), (height - (border* 2)));
        genOval(25, d);

        d.setColor(Color.gray);
        d.fillOval(x, y, 50, 50);
        gfx.drawImage(offscreen, 0, 0, this);

    }
    public int random(int low, int high)
    {
        int answer =(int)((Math.random()*(high-low))+ low);
        return answer;
    }
    public void genOval(int amount, Graphics f)
    {
        int ranWidth, ranHeight, ranX, ranY, red, blue, green;
        int i = 0;
        while(i < 25)
        {
            green = random(0,255);
            blue = random(0,255);
            red = random(0,255);

            f.setColor(new Color(red,green,blue));

            ranWidth = random(30,400);
            ranHeight = random(30,200);
            ranX = random(0 + border, ((width - border)- (ranWidth)));
            ranY = random(0 + border , ((height - border)- (ranHeight)));

            f.fillOval(ranX, ranY, ranWidth, ranHeight);
            i++;
        }   
    }

    public void update(Graphics gfx) {
        paint(gfx);
      }
}

Answer 1

你的genOval（）方法没有持久的支持。每次调用repaint（）时（通过你的线程），都会调用paint（）方法，这会为随机椭圆生成新的位置。您需要为该信息创建持久性源，如下所示：

List<Rectangle> rectangles = new ArrayList<Rectangle>();
List<Color> colors = new ArrayList<Color>();
public void init() {
    ...
    for (int i = 0; i < 25; i++) {
        int green = random(0,255);
        int blue = random(0,255);
        int red = random(0,255);

        colors.add(new Color(red,green,blue));

        ranWidth = random(30,400);
        ranHeight = random(30,200);
        ranX = random(0 + border, ((width - border)- (ranWidth)));
        ranY = random(0 + border , ((height - border)- (ranHeight)));

        rectangles.add(new Rectangle(ranX, ranY, ranWidth, ranHeight));
    }
}

public void genOval(Graphics g) {
    for (int i = 0; i < 25; i++) {
        Color color = colors.get(i);
        Rectangle rectangle = rectangle.get(i);
        // Draw using color & rectangle
    }
}

Java Applet添加线程使while循环无限

1 个答案: