java - 用Java绘制散点图

Question

我遇到了这段代码，并且一直在使用它，但是我尝试绘制的点似乎位于不正确的位置。我希望能够像图表一样绘制，因此原点 (0,0) 应该位于左下角，并且点应该相对于它绘制，有人可以帮助我吗？

package graphtest;
import javax.swing.*;
import java.awt.geom.*;
import java.awt.Graphics;
import java.util.*;

public class Scatterplot extends javax.swing.JFrame {
    private List points = new ArrayList();

    public Scatterplot() {
        super("Scatterplot");
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        points.add(new Point2D.Float(1, 4));
        points.add(new Point2D.Float(2, 10));
        points.add(new Point2D.Float(3, 12));
        //points.add(new Point2D.Float(3, 10));
       // points.add(new Point2D.Float(4, 12));

        JPanel panel = new JPanel() {  
            public void paintComponent(Graphics g) {
                //g.translate(0, 0);
                for(Iterator i=points.iterator(); i.hasNext(); ) {
                    Point2D.Float pt = (Point2D.Float)i.next();
                    g.drawString(".", (int)pt.x, (int)pt.y);
                }

            }
        };

        setContentPane(panel);
        setBounds(10, 10, 200, 200);

        setVisible(true);       
    }
    public static void main(String[] args) {
        new Scatterplot();
    }
    // <editor-fold defaultstate="collapsed" desc="Generated Code">                          
    private void initComponents() {

        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);

        javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
        getContentPane().setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGap(0, 400, Short.MAX_VALUE)
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGap(0, 300, Short.MAX_VALUE)
        );

        pack();
    }// </editor-fold>                        

    // Variables declaration - do not modify                     
    // End of variables declaration                   
}

Answer 1

您遇到的最大问题(除了不理解代码想要做什么之外)是......

1. 在进行任何自定义绘制之前，不先调用 super.paintComponent
2. 使用drawString...

使用 drawString 绘制 . 字符意味着该点将出现在您指定的 y 位置下方，因为该字符必须考虑构成字体的所有字符的整体高度。字体也会在上升线附近渲染，这也会导致 y 位置偏离。

相反，您应该更好地利用 Graphics2D API 并实际绘制点，例如......

这个示例基本上使用 Ellipse2D 来绘制点，我对其进行了设置，以便它将在指定的 x/y 坐标处绘制点的中心。

import java.awt.Color;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.geom.Ellipse2D;
import java.awt.geom.Point2D;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;

public class Scatterplot extends javax.swing.JFrame {

    private List points = new ArrayList();

    public Scatterplot() {
        super("Scatterplot");
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        points.add(new Point2D.Float(1, 4));
        points.add(new Point2D.Float(2, 10));
        points.add(new Point2D.Float(3, 12));
        //points.add(new Point2D.Float(3, 10));
        // points.add(new Point2D.Float(4, 12));

        JPanel panel = new JPanel() {
            @Override
            public void paintComponent(Graphics g) {
                //g.translate(0, 0);
                super.paintComponent(g);
                Graphics2D g2d = (Graphics2D) g.create();
//                g.setColor(Color.RED);
//                g.drawRect(0, 0, getWidth() - 1, getHeight() - 1);
                g.setColor(Color.BLACK);
                for (Iterator i = points.iterator(); i.hasNext();) {
                    Point2D.Float pt = (Point2D.Float) i.next();
                    Ellipse2D dot = new Ellipse2D.Float(pt.x - 1, pt.y - 1, 2, 2);
                    g2d.fill(dot);
                }
                g2d.dispose();
            }
        };

        setContentPane(panel);
        setBounds(10, 10, 200, 200);

        setVisible(true);
    }

    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                    ex.printStackTrace();
                }

                new Scatterplot();
            }
        });
    }
}

看看2D Graphics了解更多详情