多線程圖形 (multithreading Graphics)

問題描述

多線程圖形 (multithreading Graphics)

我正在嘗試實現一個程序，在該程序中我繪製多個圓圈並讓它們隨機穿過框架。我想為每個圈子創建一個線程，但由於某種原因它不起作用。當我實例化幾個圓圈時，框架中只出現一個。這是我的代碼

import java.awt.*;
import javax.swing.*;

public class Ball extends JPanel implements Runnable {
    private Color color;
    private int xPosition;
    private int yPosition;
    private int xDir;
    private int yDir;
    private int radius;
    private int xSpeed;
    private int ySpeed;
    private static JFrame frame;

    public Ball(int xPos, int yPos) 
    {
        color = new Color((int) (Math.random()*254), (int) (Math.random()*254), (int) (Math.random()*254));
        System.out.println(color);
        radius = 10;
        xPosition = xPos;
        yPosition = yPos;
        xDir = ‑1;
        yDir = ‑1;
        xSpeed = 10;
        ySpeed = 10;

    }

    public void paint(Graphics e){
        super.paint(e);
        Graphics2D g = (Graphics2D) e;
        g.setColor(color);
        g.fillOval(xPosition, yPosition, radius, radius);     
        //setSpeed();
    }

    public void setSpeed()
    {
        xSpeed = (int) (Math.random() * 10);
    }

    public void moveBall()
    {
        if(xPosition >= 390)
        {
            xDir *= ‑1;
        }
        else if(xPosition <= 0)
        {
            xDir *= ‑1;
        }
        if(yPosition >= 390)
        {
            yDir *= ‑1;
        }
        else if(yPosition <= 0)
        {
            yDir *= ‑1;
        }
        xPosition = xPosition + ( xDir * xSpeed);
        yPosition  = yPosition + (yDir * ySpeed);


    }


    public static void main(String[] args) {
        // TODO Auto‑generated method stub
        frame = new JFrame("Ball Bouncer");
        frame.setSize(400, 400);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        Ball b1 = new Ball(25, 25);
        Ball b2 = new Ball(50, 50);
        b1.setSpeed();
        //b2.setSpeed();
        Thread a1 = new Thread(b1);
        Thread a2 = new Thread(b2);

        frame.setVisible(true);
        System.out.println(a2.getState());

        a1.start();

        a2.start();
        System.out.println(a1.getId());
        System.out.println(a2.getId());

    }

    @Override
    public void run() {
        while(true)
        {
            frame.getContentPane().add(this);

            moveBall();
            repaint();
            try {
                Thread.sleep(100);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }


        }

    }

}

參考解法

方法 1:

Ball (Your class) extends JPanel.

If you add more than one JPanel to a JFrame, only last one you added will be visible.

(by Ihsan Hashem、Mayuso)

參考文件

1. multithreading Graphics (CC BY‑SA 2.5/3.0/4.0)