如何消除java动画闪烁

Question

我正在编写一个需要在屏幕上平滑滚动波形的 java 应用程序。我花了很长时间阅读各种教程来弄清楚如何使这个动画尽可能流畅。据我所知，我已经做了所有正常的事情来消除闪烁（绘制到屏幕外缓冲区并一步渲染，加上覆盖更新，因此屏幕不会空白），但我的动画仍然闪烁，并且屏幕好像每次更新前都被清空了。

我确信我缺少一些基本的（可能很简单），但我没有想法。我将在下面发布一个说明问题的课程。任何帮助将不胜感激。

import java.awt.*;
import javax.swing.*;

public class FlickerPanel extends JPanel implements Runnable {

    private float [] pixelMap = new float[0];

    /** Cached graphics objects so we can control our animation to reduce flicker **/
    private Image screenBuffer;
    private Graphics bufferGraphics;

    public FlickerPanel () {
        Thread t = new Thread(this);
        t.start();
    }

    private float addNoise () {
        return (float)((Math.random()*2)-1);
    }

    private synchronized void advance () {
        if (pixelMap == null || pixelMap.length == 0) return;
        float [] newPixelMap = new float[pixelMap.length];
        for (int i=1;i<pixelMap.length;i++) {
            newPixelMap[i-1] = pixelMap[i];
        }

        newPixelMap[newPixelMap.length-1] = addNoise();     

        pixelMap = newPixelMap;
    }

    public void run() {
        while (true) {
            advance();
            repaint();

            try {
                Thread.sleep(25);
            } catch (InterruptedException e) {}

        }
    }

    private int getY (float height) {
        double proportion = (1-height)/2;
        return (int)(getHeight()*proportion);
    }

    public void paint (Graphics g) {

        if (screenBuffer == null || screenBuffer.getWidth(this) != getWidth() || screenBuffer.getHeight(this) != getHeight()) {
            screenBuffer = createImage(getWidth(), getHeight());
            bufferGraphics = screenBuffer.getGraphics();
        }

        if (pixelMap == null || getWidth() != pixelMap.length) {
            pixelMap = new float[getWidth()];
        }

        bufferGraphics.setColor(Color.BLACK);

        bufferGraphics.fillRect(0, 0, getWidth(), getHeight());

        bufferGraphics.setColor(Color.GREEN);

        int lastX = 0;
        int lastY = getHeight()/2;

        for (int x=0;x<pixelMap.length;x++) {
            int y = getY(pixelMap[x]);
            bufferGraphics.drawLine(lastX, lastY, x, y);
            lastX = x;
            lastY = y;
        }

        g.drawImage(screenBuffer, 0, 0, this);
    }

    public void update (Graphics g) {
        paint(g);
    }

    public static void main (String [] args) {
        JFrame frame = new JFrame("Flicker test");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setContentPane(new FlickerPanel());
        frame.setSize(500,300);
        frame.setVisible(true);
    }


}

Answer 1

1. 在JPanel 中，覆盖paintComponent(Graphics) 而不是paint(Graphics)
2. 而不是调用 Thread.sleep(n) 实现一个 Swing Timer 用于重复任务或一个 SwingWorker 用于长时间运行的任务。 有关详细信息，请参阅Concurrency in Swing。

Answer 2

JPanel 默认情况下是双缓冲的，“Swing 程序应该覆盖paintComponent() 而不是覆盖paint()。”—Painting in AWT and Swing: The Paint Methods。将覆盖 paintComponent() 的 example 与覆盖 paint() 的 example 进行对比。

附录：剪切是由在每次更新时创建和复制整个图像引起的。相反，在每次迭代时在GeneralPath 和draw() 和Shape 上累积点数，如here 所示。