Question

我正在创建一个RandomWalk计划。大多数程序都在按预期工作，但是有一个主要问题。

当绘制PolyLine时，它会继续被强制回原点（0,0）而不是最后一个点。我一直试着看看我错过了什么/做错了什么，但我无法找到问题。

任何帮助将不胜感激;如果需要更多信息，请问。感谢。

主要类

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

public class RandomWalk {
    public static void main (String[] args) {

        // Creating main frame
        JFrame main = new JFrame("RandomWalk - Version 1.0");
        main.setSize(800, 800);
        main.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        main.setResizable(false);
        main.setLocationRelativeTo(null);

        // Creating content/container panel
        JPanel container = new JPanel();
        container.setLayout(new BoxLayout(container, BoxLayout.PAGE_AXIS));
        main.setContentPane(container);

        // Creating scene/canvas
        Draw canvas = new Draw();
        canvas.setAlignmentX(Component.CENTER_ALIGNMENT);

        container.add(canvas);

        main.toFront();
        main.setVisible(true);
    }
}

绘图类

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

public class Draw extends JPanel {

    // Starting value for i
    public static int i = 1;

    // Increment for line length
    public static int inc = 10;

    // Choose amount of lines/moves
    public static int a = 10000;

    // Arrays for polyline points
    public static int[] xPoints = new int[a];
    public static int[] yPoints = new int[a];

    public Timer timer = new Timer(5, new ActionListener() {
        public void actionPerformed(ActionEvent e) {
            xPoints[0] = 400;
            yPoints[0] = 400;

            if (i < a) {

                double r = Math.random();

                if (r < 0.25) {
                    xPoints[i] = xPoints[i - 1] - inc;
                    yPoints[i] = yPoints[i - 1] - 0;
                    i++;
                } else if (r < 0.50) {
                    xPoints[i] = xPoints[i - 1] + inc;
                    yPoints[i] = yPoints[i - 1] + 0;
                    i++;
                } else if (r < 0.75) {
                    yPoints[i] = yPoints[i - 1] - inc;
                    xPoints[i] = xPoints[i - 1] - 0;
                    i++;
                } else if (r < 1.00) {
                    yPoints[i] = yPoints[i - 1] + inc;
                    xPoints[i] = xPoints[i - 1] + 0;
                    i++;
                }
                repaint();
            }
        }
    });

    public void paintComponent(Graphics g) {

        timer.start();

        g.drawPolyline(xPoints, yPoints, xPoints.length);
    }
}

Answer 1

您想使用g.drawPolyline(xPoints, yPoints, i);而不是g.drawPolyline(xPoints, yPoints, xPoints.length);。

这是因为如果您使用xPoints.length，即使您尚未初始化xPoints和{{}}，也要告诉它使用您的整个yPoints和xPoints[j]数组所有yPoints[j]都{1}}（因此它们都是j > i）。如果您使用0作为长度，它将只读取那些数组，直到索引i，并且一切都很好。

为什么我的PolyLine会从原点（0,0）继续绘制？

1 个答案: