Java repaint()混淆

Question

我有一个程序，打开一个窗口，迅速改变背景的颜色，并随机弹出矩形和椭圆。我的代码可以工作，但我不知道为什么，因为我没有在代码中调用repaint()函数。当我在我的个人update()函数中包含repaint()函数时，我没有看到任何明显的变化。下面是我的代码：

package epilepsy;

import java.awt.Color;
import java.awt.Graphics;
import java.awt.BorderLayout;

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

import Math.Math;

/**
 *
 * @author 21psuby
 */
public class Epilepsy {

    JFrame frame;
    DrawPanel drawPanel;
    Math math = new Math();

    int screenW = 800;
    int screenH = 700;

    int red = math.random(0, 255);
    int green = math.random(0, 255);
    int blue = math.random(0, 255);
    int x = math.random(0, screenW);
    int y = math.random(0, screenH);
    int w = math.random(0, screenW/2);
    int h = math.random(0, screenH/2);

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        new Epilepsy().go();
    }

    private void go() {
        frame = new JFrame();
        drawPanel = new DrawPanel();

        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.getContentPane().add(BorderLayout.CENTER, drawPanel);
        frame.setVisible(true);
        frame.setSize(screenW, screenH);
        frame.setLocationRelativeTo(null);
        frame.setResizable(false);
    }

    class DrawPanel extends JPanel {

        private static final long serialVersionUID = 1L;

        public void paintComponent(Graphics g) {
            randomize();
            frame.setBackground(new Color(red, green, blue));
            randomize();
            g.setColor(new Color(red, green, blue));
            g.fillRect(x, y, w, h);
            randomize();
            g.setColor(new Color(red, green, blue));
            g.fillRect(x, y, w, h);
            randomize();
            g.setColor(new Color(red, green, blue));
            g.fillRect(x, y, w, h);
            randomize();
            g.setColor(new Color(red, green, blue));
            g.fillOval(x, y, w, h);
            randomize();
            g.setColor(new Color(red, green, blue));
            g.fillOval(x, y, w, h);
            randomize();
            g.setColor(new Color(red, green, blue));
            g.fillOval(x, y, w, h);
        }
    }

    private void randomize() {
        red = math.random(0, 255);
        green = math.random(0, 255);
        blue = math.random(0, 255);
        x = math.random(0, screenW);
        y = math.random(0, screenH);
        w = math.random(0, screenW/2);
        h = math.random(0, screenH/2);
    }

    private void update() {
        while (true) {
            try {
                Thread.sleep(10);
            } catch (Exception e) {
                e.printStackTrace();
            }
            frame.repaint();
        }
    }
}

谢谢，Pranav

Answer 1

在内部某个地方使用setBackground方法会导致框架重新绘制自身，它会再次调用您的paintComponent，然后再调用setBackground。这就产生了无限循环。删除setBackground行，它应该可以正常工作。如果您想更改面板的背景，请尝试将其设置在paintComponent方法之外，或者在整个面板上绘制一个所需颜色的矩形。