如何在Java中实现非破坏性绘画？

Question

我想在面板上绘制许多具有不同频率的正弦体，但是由于绘画具有破坏性，所以我无法实现这一目标。我只能看到最后一个正弦曲线绘制。

在代码中，generatesInus（）方法仅称为3次，但可能被称为多次，我不想为paintComponent（）方法中的每个正弦曲线调用g.filloval（）方法。

有没有一种方法可以实现非破坏性绘画并看到所有具有不同频率的鼻窦药？

请参阅下面的代码：

package testdrawsinus;

import java.awt.Color;
import java.awt.Graphics;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;

import javax.swing.JFrame;
import javax.swing.JPanel;

public class TestDrawSinus extends JPanel 
{
   private static double[] x;
   private static double[] y;
   private static boolean buttonClicked = false;
   private static JPanel panel = new TestDrawSinus();
   
   @Override
   public void paintComponent(Graphics g) 
   {
      super.paintComponent(g);
      g.setColor(Color.GREEN);
      if (buttonClicked)
      {          
          for (int i=0; i<x.length; i++)
          {                   
             g.fillOval((int)x[i] + panel.getWidth()/2, -1*((int)y[i]) + panel.getHeight()/2, 10, 10);                          
          }
          buttonClicked = false;
      }
   }

   private static void generateSinus(int freq)
   {
      x = new double[200];
      y = new double[200];
      for (int i=0; i<=199; i++)
      {
         x[i]= (double)i;
         y[i] = 100*Math.sin(2*Math.PI*freq*i/200);
              
      }
   }

   public static void main(String[] args) 
   {
      JFrame frame = new JFrame();  
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      frame.setLayout(null);
      frame.setSize(800, 600);
      frame.setLocationRelativeTo(null);
      frame.setVisible(true);

      panel.setLayout(null);
      panel.setBounds(20,20, 700,400);
      panel.setBackground(Color.BLACK);
      frame.add(panel);

      JButton button1 = new JButton();
      button1.setText("plot");
      button1.setBounds(300, 500, 150, 50);
      frame.add(button1);

      button1.addActionListener(new ActionListener() 
      {
         @Override
         public void actionPerformed(ActionEvent e) 
         {                   
           buttonClicked = true; 
           generateSinus(1);
           panel.repaint();
           generateSinus(2);
           panel.repaint();
           generateSinus(3);
           panel.repaint();
         }
               
      });              
   }
}

感谢您的帮助。

Answer 1

您可能有多种方法可以做到这一点，一种方法是将每个系列分开为自己的型号，然后将每个模型的面板涂料都涂上，例如...

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.geom.Ellipse2D;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;
import java.util.Random;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;

public class Main {
    public static void main(String[] args) {
        new Main();
    }

    private Color[] masterColors = new Color[]{
        Color.BLACK, Color.BLUE, Color.CYAN, Color.DARK_GRAY,
        Color.GREEN, Color.MAGENTA, Color.ORANGE, Color.PINK,
        Color.RED, Color.WHITE, Color.YELLOW
    };

    public Main() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                TestDrawSinus sinusPane = new TestDrawSinus();

                JFrame frame = new JFrame();
                frame.add(sinusPane);

                JButton button1 = new JButton();
                button1.setText("plot");
                frame.add(button1, BorderLayout.SOUTH);

                button1.addActionListener(new ActionListener() {
                    private List<Color> colors = new ArrayList<>();
                    private int freq = 0;

                    @Override
                    public void actionPerformed(ActionEvent e) {
                        sinusPane.addSinusPlot(generateSinus(++freq, nextColor()));
                        sinusPane.addSinusPlot(generateSinus(++freq, nextColor()));
                        sinusPane.addSinusPlot(generateSinus(++freq, nextColor()));
                    }

                    protected Color nextColor() {
                        if (colors.isEmpty()) {
                            colors.addAll(Arrays.asList(masterColors));
                            Collections.shuffle(colors);
                        }
                        return colors.remove(0);
                    }

                });

                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    private Random rnd = new Random();

    private SinusPlot generateSinus(int freq, Color color) {
        double[] x = new double[200];
        double[] y = new double[200];
        for (int i = 0; i < 200; i++) {
            x[i] = (double) i;
            y[i] = 100 * Math.sin(2d * Math.PI * freq * i / 200d);
        }
        return new SinusPlot(x, y, color);
    }

    public class SinusPlot {
        private double[] x;
        private double[] y;
        private Color color;

        public SinusPlot(double[] x, double[] y, Color color) {
            this.x = x;
            this.y = y;
            this.color = color;
        }

        public int getSize() {
            return x.length;
        }

        public double getXAt(int index) {
            return x[index];
        }

        public double getYAt(int index) {
            return y[index];
        }

        public Color getColor() {
            return color;
        }

    }

    public class TestDrawSinus extends JPanel {
        private List<SinusPlot> plots = new ArrayList<>(8);

        public void addSinusPlot(SinusPlot plot) {
            plots.add(plot);
            repaint();
        }

        @Override
        public Dimension getPreferredSize() {
            return new Dimension(800, 600);
        }

        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            Graphics2D g2d = (Graphics2D) g.create();
            for (SinusPlot plot : plots) {
                System.out.println(plot.getColor());
                g2d.setColor(plot.getColor());
                for (int i = 0; i < plot.getSize(); i++) {
                    Ellipse2D dot = new Ellipse2D.Double(((getWidth() - plot.getSize()) / 2) + plot.getXAt(i), plot.getYAt(i) + getHeight() / 2, 10, 10);
                    g2d.fill(dot);
                }
            }
            g2d.dispose();
        }
    }
}

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