java - 如何在Java中实现Graphic2D对象的颜色变化？

Question

我试图了解是否可以在应用程序运行时更改现有图形的颜色(多种不同颜色之间的闪烁)。

我有一个使用 GeneralPath 类绘制的起始形状，并且我还有一个正常工作的随机 RGB 颜色代码选择器。是否可以使用 repaint(); 更改颜色，让我的星星的颜色在从 createRandomColor() 中随机选择的 3 个选定颜色之间变化方法？

代码

import java.awt.Canvas;
import java.awt.Color;
import java.awt.Container;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.geom.GeneralPath;
import java.awt.geom.Rectangle2D;
import static java.lang.Math.random;
import java.util.Vector;
import javax.swing.JApplet;
import javax.swing.JFrame;
import javax.swing.JPanel;
import java.util.ArrayList;
import java.util.List;
import java.util.Random;

public class Sandbox extends JApplet {
    DrawingStar canvas;

    public static void main(String[] args) {
        JFrame frame = new JFrame();
        Sandbox path = new Sandbox();
        path.init();
        frame.getContentPane().add(path);
        frame.setSize(250, 250);
        frame.setVisible(true);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    }

    public void init() {
        Container container = getContentPane();
        canvas = new DrawingStar();
        container.add(canvas);
    }

}

class DrawingStar extends Canvas {
    Vector generalPaths;
    private List<Color> colors;

    public DrawingStar() {
        colors = new ArrayList<Color>();

        for (int i = 0; i < 3; i++) {
            colors.add(createRandomColor());
        }

        setBackground(Color.white);
        setSize(400, 400);
        generalPaths = new Vector();

        GeneralPath gp1;

        gp1 = new GeneralPath();
        gp1.moveTo(50, 120);
        gp1.lineTo(70, 180);
        gp1.lineTo(20, 140);
        gp1.lineTo(80, 140);
        gp1.lineTo(30, 180);
        gp1.closePath();
        generalPaths.addElement(gp1);
    }

    public void paint(Graphics g) {
        Graphics2D g2D = (Graphics2D) g;
        g2D.translate(70.0f, -85.0f);
        g2D.draw((GeneralPath) generalPaths.elementAt(0));

        for (int i = 0; i < 3; i++) {
            Color color = colors.get(i);
            g2D.setColor(color);
            g2D.fill((GeneralPath) generalPaths.elementAt(0));
        }

        System.out.println("Is this working");
        repaint();
    }


    private Color createRandomColor(){
        int r = (int) (Math.random() * 256);
        int g = (int) (Math.random() * 256);
        int b = (int) (Math.random() * 256);
        Color color = new Color(r,g,b);

        return color;
    }

}

Answer 1

小程序已死，HTML5 万岁

• Why were applets deprecated in JDK 9?
• Oracle reveals Java Applet API deprecation plan
• DK 9 Release NotesDeprecated APIs, Features, and Options
• The clock is ticking: The Java browser plugin will be deprecated soon
• Oracle Reminds Java Developers That Soon They Won’t Have a Browser to Run Applets

是时候继续了……而且，小程序的生命周期比您实现的要复杂得多。

“替代方案”

• Creating a GUI With JFC/Swing
• Performing Custom Painting
• Painting in AWT and Swing
• How to Use Swing Timers

Canvas 是一个低级组件，可能不太适合您的需求。它也不是双缓冲的，因此重新绘制时会出现闪烁。

不要从任何绘制方法中调用repaint，您不会喜欢结果。相反，安排在将来的某个时间进行更新。

此示例仅使用 Swing Timer 充当伪循环，每秒递增计数器并获取下一个颜色并调用重绘。

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.GeneralPath;
import java.util.ArrayList;
import java.util.List;
import java.util.Vector;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.Timer;

public class Sandbox {

    DrawingStar canvas;

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

    public Sandbox() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                JFrame frame = new JFrame();
                canvas = new DrawingStar();
                frame.getContentPane().add(canvas);
                frame.setSize(250, 250);
                frame.setVisible(true);
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
            }
        });
    }

    class DrawingStar extends JPanel {

        Vector generalPaths;
        private List<Color> colors;
        private int colorIndex = 0;
        private Color color;

        public DrawingStar() {

            colors = new ArrayList<Color>();

            for (int i = 0; i < 3; i++) {
                colors.add(createRandomColor());
            }

            color = colors.get(0);

            setBackground(Color.white);
            generalPaths = new Vector();

            GeneralPath gp1;

            gp1 = new GeneralPath();
            gp1.moveTo(50, 120);
            gp1.lineTo(70, 180);
            gp1.lineTo(20, 140);
            gp1.lineTo(80, 140);
            gp1.lineTo(30, 180);
            gp1.closePath();
            generalPaths.addElement(gp1);

            Timer timer = new Timer(1000, new ActionListener() {
                @Override
                public void actionPerformed(ActionEvent e) {
                    colorIndex++;
                    if (colorIndex >= colors.size()) {
                        colorIndex = 0;
                    }

                    color = colors.get(colorIndex);
                    repaint();
                }
            });
            timer.start();
        }

        @Override
        public Dimension getPreferredSize() {
            return new Dimension(400, 400);
        }

        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g); //To change body of generated methods, choose Tools | Templates.
            Graphics2D g2D = (Graphics2D) g;
            g2D.translate(70.0f, -85.0f);
            g2D.draw((GeneralPath) generalPaths.elementAt(0));

            g2D.setColor(color);
            g2D.fill((GeneralPath) generalPaths.elementAt(0));
        }

        private Color createRandomColor() {
            int r = (int) (Math.random() * 256);
            int g = (int) (Math.random() * 256);
            int b = (int) (Math.random() * 256);
            Color color = new Color(r, g, b);

            return color;
        }

    }
}

Swing 不是线程安全的并且是单线程的，因此使用 Swing Timer