Checkers Applet问题

Question

我正在编写一个小程序，使得棋子以相同的速度来回运行。然而，底部检查器的运行速度比顶部检查器快得多。我如何纠正它，使它们来回以相同的速度运行。我猜测它与for循环有关但我无法弄明白。

import java.awt.*; 

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

public class Checkers extends java.applet.Applet implements Runnable {

  Thread runner;
  int x1pos;
  int x2pos;
  Image offscreenImg;
  Graphics offscreenG;

  public void init() {
    offscreenImg = createImage(this.size().width, this.size().height);
    offscreenG = offscreenImg.getGraphics();
  }

  public void start() {
    if (runner == null); {
      runner = new Thread(this);
      runner.start();
    }
  }

  public void stop() {
    if (runner != null) {
      runner.stop();
      runner = null;
    }
  }

  public void run() {
    while (true) {
      for (x1pos = 5; x1pos <= 105; x1pos+=4)
      {
      for (x2pos = 105; x2pos >= 5; x2pos-=4)
       {
        repaint ();
        try { Thread.sleep(10); }
        catch (InterruptedException e) { }
      }
      repaint();
        try { Thread.sleep(100); }
        catch (InterruptedException e) { }
       }
     x1pos = 5;
     x2pos = 105;
    }
  }

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


  public void paint(Graphics g) {
    // Draw background onto the buffer area
    offscreenG.setColor(Color.black);
    offscreenG.fillRect(0,0,100,100);
    offscreenG.setColor(Color.blue);
    offscreenG.fillRect(100,0,100,100);
    offscreenG.setColor(Color.blue);
    offscreenG.fillRect(0,100,100,100);
    offscreenG.setColor(Color.black);
    offscreenG.fillRect(100,100,100,100);

    // Draw checker
    offscreenG.setColor(Color.red);
    offscreenG.fillOval(x1pos,5,90,90);
    offscreenG.setColor(Color.green);
    offscreenG.fillOval(x2pos,105,90,90);


    // Now, transfer the entire buffer onto the screen
    g.drawImage(offscreenImg,0,0,this);
  }
  public void destroy() {
     offscreenG.dispose();
  }
}

谢谢

Answer 1

您的run语句中的循环是嵌套的。这意味着每次更新x1pos时，都会将x2pos从105更新为5.

你的for循环应该读（尽可能与你的相似）

  for (x1pos = 5, x2pos = 105; x1pos <= 105 && x2pos >= 5 ; x1pos+=4, x2pos-=4)
  {
    repaint ();
    try { Thread.sleep(10); }
    catch (InterruptedException e) { }
  }