Question

我有一个名为theLayers的ArrayList，它存储点（层）的集合，我希望每一层都具有不同的颜色。在for循环的每次迭代中，我将图形设置为新颜色并绘制每个不同层的点。但是，在调试时，我注意到这些点设置为生成的最后一种颜色。

我尝试将随机颜色分配放置在代码中的不同位置，并且调试了代码以确保在每次迭代期间确实更改颜色。

import java.awt.BasicStroke;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Point;
import java.util.ArrayList;
import javax.swing.JPanel;

public class Drawer extends JPanel {
private ArrayList<ArrayList<Point>> theLayers;

public Drawer() {
    this(new ArrayList<ArrayList<Point>>());
}

public Drawer(ArrayList<ArrayList<Point>> coordinates) {
    this.theLayers = new ArrayList<ArrayList<Point>>(coordinates);
}

public void paintComponent(Graphics g) {
super.paintComponent(g);

Graphics2D g2d = (Graphics2D) g;

g2d.setStroke(new BasicStroke(3));
for(ArrayList<Point> coordinates:theLayers) {
    int R = (int) (Math.random( )*256);
    int G = (int)(Math.random( )*256);
    int B= (int)(Math.random( )*256);
    Color randomColor = new Color(R, G, B);
    g2d.setColor(randomColor);
    for (int i = 0; i < coordinates.size(); i++) {
        g2d.drawLine(coordinates.get(i).x, coordinates.get(i).y,
                coordinates.get(i).x, coordinates.get(i).y);
    }
}
}
}

我希望每一层的颜色都不同，而不是相同的颜色。谢谢。

Answer 1

如camickr所述，有一个具有颜色属性的自定义点对象：

class ColoredPoint extends Point{

    private final Color color;

    ColoredPoint(int x, int y,Color color) {
        super(x, y);
        this.color = color;
    }

    Color getColor() {
        return color;
    }
}

并在Drawer类中使用它：

class Drawer extends JPanel {

    private final ArrayList<ArrayList<ColoredPoint>> theLayers;
    private static final int W = 700, H =700;
    public Drawer() {
        this(new ArrayList<ArrayList<ColoredPoint>>());
    }

    public Drawer(ArrayList<ArrayList<ColoredPoint>> coordinates) {
        theLayers = new ArrayList<>(coordinates);
        setPreferredSize(new Dimension(W,H));
    }

    @Override
    public void paintComponent(Graphics g) {
        super.paintComponent(g);
        Graphics2D g2d = (Graphics2D) g;
        g2d.setStroke(new BasicStroke(3));

        for(ArrayList<ColoredPoint> cPoints:theLayers) {
            g2d.setColor(cPoints.get(0).getColor());
            for (int i = 0; i < cPoints.size(); i++) {
                g2d.drawLine(cPoints.get(i).x, cPoints.get(i).y,
                        cPoints.get(i).x, cPoints.get(i).y);
            }
        }
    }
}

将此link用于mcve。复制并将整个代码粘贴到一个文件（SwingTestFrame.java）中并运行。

如何在Java中的for循环的每次迭代中更改线条的颜色

1 个答案: