我如何制作不会更新的 JPanel 背景？

Question

我正在尝试制作一个具有一些不断变化的颜色和移动形状的动画屏幕保护程序，我还希望它具有某种轨迹效果（例如，如果您不这样做，每个像素上的最新颜色会如何不断地绘制在那里'设置你的背景颜色）。我以前实现过一次这个效果，但我不知道我是怎么做到的。目前的结果是一个移动的正方形，它在灰色背景上改变颜色。 ScreenSaver.java

import java.awt.Color;
import java.awt.Component;
import java.awt.Graphics;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.JPanel;
import javax.swing.Timer;

public class ScreenSaver extends JPanel
{
    public static Component sc;
    public int delay = 1000/2;
    public int state = 0;
    public int re = 255;
    public int gr = 0;
    public int bl = 0;
    public int d = 1;
    ScreenSaver()
    {
        ActionListener counter = new ActionListener()
        {
            public void actionPerformed(ActionEvent event)
            {
                updateUI();
                repaint();
            }
        };
        new Timer(delay, counter).start();
        System.out.println("this is the secret screensaver that appears after 30 seconds of no mouse activity");//i have this line here so it doesn't print every time the screen updates
    }

    public void paintComponent(Graphics g)
    {
        super.paintComponent(g);
        this.setBackground(null);
        if (state == 0)
        {
            gr++;
            if(gr == 255)
                state = 1;
        }
        if (state == 1)
        {
            re--;
            if(re == 0)
                state = 2;
        }
        if (state == 2)
        {
            bl++;
            if(bl == 255)
                state = 3;
        }
        if (state == 3)
        {
            gr--;
            if(gr == 0)
                state = 4;
        }
        if (state == 4)
        {
            re++;
            if(re == 255)
                state = 5;
        }
        if (state == 5)
        {
            bl--;
            if(bl == 0)
                state = 0;
        }
        g.setColor(new Color(re, gr, bl));
        d++;
        g.fillRect(d, 50, 50, 50);
    }
    public static void main(String[] args)
    {
        //ScreenSaver sc = new ScreenSaver();
    }
}

Main.java：（ScreenSaver.java通过这个文件作为对象调用）

import java.awt.Color;
import java.awt.Graphics;
//import java.util.Random;

//import javax.swing.AbstractAction;
//import javax.swing.Action;
import javax.swing.JFrame;
import javax.swing.JPanel;

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import java.awt.event.MouseEvent;
import java.awt.event.MouseMotionListener;

import javax.swing.Timer;

public class FinalProject extends JPanel implements MouseMotionListener
{
    public int delay = 1000/2;
    public boolean screenActive = true;
    public int why = 1;
    FinalProject()
    {
        ActionListener counter = new ActionListener()
        {
            public void actionPerformed(ActionEvent event)
            {
                updateUI();
                repaint();
            }
        };
        new Timer(delay, counter).start();
    }
    static JFrame jf = new JFrame();

    public void paintComponent(Graphics g)
    {
        super.paintComponent(g);
        this.setBackground(Color.BLACK);
        if (screenActive)
        {
            why++;
        }
        if (why == 6)
        {
            why = 0;
            System.out.println("inactivity detected");
            screenActive = false;
            ScreenSaver sc = new ScreenSaver();
            jf.add(sc);
        }
    }

    public static void main(String[] args) throws InterruptedException
    {
        System.out.println("Welcome to Computer Simulator 0.1");
        System.out.println("this is the main screen");
        FinalProject e = new FinalProject();
        //ScreenSaver sc = new ScreenSaver();
        jf.setTitle("game");
        jf.setSize(500,500);
        //jf.setUndecorated(true);
        //jf.setBackground(new Color(1.0f,1.0f,1.0f,0.5f));
        jf.setVisible(true);
        jf.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        //jf.add(new ScreenSaver());
        jf.add(e);
    }

    @Override
    public void mouseDragged(MouseEvent arg0) {
        // TODO Auto-generated method stub

    }

    @Override
    public void mouseMoved(MouseEvent MOUSE_MOVED)
    {

    }
}

Answer 1

不要调用 updateUI()。您只需要 repaint() 即可使组件重新绘制自身。

一种方法是对 BufferedImage 进行绘图，然后使用 BufferedImage 创建一个 ImageIcon，然后将其添加到 JLabel。

另一种方法是保留一个要绘制的对象列表，然后在每次重新绘制组件时循环访问该列表。

查看 Custom Painting Approches 工作示例和分析何时可以使用任何一种方法。

我如何制作不会更新的 JPanel 背景？

how do i make a JPanel background that won't update?

java

swing

background

awt

screensaver