别以为Swing有双缓冲就够了，变态时三缓冲是很有必要的
AWT时代必须自己实现双缓冲机制，否则绘画时界面总是闪烁。
Swing的JComponent以及其子类的绘制默认是使用了双缓冲的，例如JPanel，方便了不少。
但是，当在Swing中绘制几千个图元时，如果绘图仍然是直接对Swing的Back-buffer进行操作，速度会非常的慢，甚至慢到没法忍受。例如下面的例子里有16385个点，共画16384条线，改变窗口的大小，就可以发现直接操作Swing的Back-buffer是多么的令人难以忍受。
这个时候，使用三缓冲(triple-buffer)是很有必要的：先把这些图元绘制到自己创建的缓冲图像里，然后再一次性的把此缓冲图像交给Swing后台绘制，速度的提升是非常非常的大的。
只有两个Java文件，就不打包了。
import java.awt.Color;import java.awt.Graphics;import java.awt.Graphics2D;import java.awt.GraphicsConfiguration;import java.awt.GraphicsDevice;import java.awt.GraphicsEnvironment;import java.awt.RenderingHints;import java.awt.Transparency;import java.awt.event.ActionEvent;import java.awt.event.ActionListener;import java.awt.geom.Point2D;import java.awt.image.BufferedImage;import java.util.ArrayList;import java.util.List;import javax.swing.JFrame;import javax.swing.JPanel;import javax.swing.SwingUtilities;import javax.swing.Timer;import util.GeometryUtil;@SuppressWarnings("serial")public class Growing extends JPanel { private List<Point2D> ps = new ArrayList<Point2D>(); private Timer timer; private boolean stopped = false; public Growing() { ps.add(new Point2D.Double(0, 0)); ps.add(new Point2D.Double(800, 0)); timer = new Timer(500, new ActionListener() { @Override public void actionPerformed(ActionEvent e) { grow(); repaint(); } }); timer.start(); } public void grow() { if (stopped) { return; } List<Point2D> temp = new ArrayList<Point2D>(); temp.add(ps.get(0)); for (int i = 0; i < ps.size() - 1; ++i) { Point2D p0 = ps.get(i); Point2D p4 = ps.get(i + 1); double len = GeometryUtil.distanceOfPoints(p0, p4); if (len < 0.5) { // 当线条长度小于1时，就停止再增长 System.out.println(ps.size()); timer.stop(); return; } Point2D p1 = GeometryUtil.extentPoint(p0, p4, len / 3); Point2D p3 = GeometryUtil.extentPoint(p0, p4, len * 2 / 3); Point2D p2 = GeometryUtil.rotate(p3.getX(), p3.getY(), p1.getX(), p1.getY(), 60); temp.add(p1); temp.add(p2); temp.add(p3); temp.add(p4); } ps = null; ps = temp; temp = null; } @Override protected void paintComponent(Graphics g) { super.paintComponent(g); Graphics2D g2d = (Graphics2D) g; // 修改type的值使用不同的绘制方式，1为compatible image, 2为swing的back-buffer int type = 1; // 改变窗口的大小，可以看到直接对intermediate image操作比直接对swing back-buffer操作快很多. // 所以有很多绘制操作时，使用triple buffer是很有必要的(因为Swing已经默认使用了双缓冲). if (type == 1) { // [[[1]]]: 操作 compatible image 速度非常快 renderWithBuf(g2d, getWidth(), getHeight()); } else { // [[[2]]]: 操作Swing的 back-buffer 速度非常慢 render(g2d, getWidth(), getHeight()); } } private BufferedImage bufImg; protected void renderWithBuf(Graphics2D g2d, int w, int h) { if (bufImg == null || bufImg.getWidth() != w || bufImg.getHeight() != h) { bufImg = createCompatibleImage(w, h, Transparency.OPAQUE); // bufImg = new BufferedImage(w, h, BufferedImage.TYPE_INT_RGB); } Graphics2D gg = bufImg.createGraphics(); render(gg, w, h); gg.dispose(); g2d.drawImage(bufImg, 0, 0, null); } protected void render(Graphics2D g2d, int w, int h) { g2d.setBackground(Color.BLACK); g2d.clearRect(0, 0, w, h); g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON); g2d.translate(0, h - 20); g2d.setColor(Color.WHITE); for (int i = 0; i < ps.size() - 1; ++i) { Point2D sp = ps.get(i); Point2D ep = ps.get(i + 1); g2d.drawLine((int) sp.getX(), -(int) sp.getY(), (int) ep.getX(), -(int) ep.getY()); } } // 创建硬件适配的缓冲图像，为了能显示得更快速 public static BufferedImage createCompatibleImage(int w, int h, int type) { GraphicsEnvironment env = GraphicsEnvironment.getLocalGraphicsEnvironment(); GraphicsDevice device = env.getDefaultScreenDevice(); GraphicsConfiguration gc = device.getDefaultConfiguration(); return gc.createCompatibleImage(w, h, type); } private static void createGuiAndShow() { JFrame frame = new JFrame("Growing"); frame.getContentPane().add(new Growing()); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); frame.setSize(800, 400); frame.setAlwaysOnTop(true); frame.setLocationRelativeTo(null); frame.setVisible(true); } public static void main(String[] args) { SwingUtilities.invokeLater(new Runnable() { @Override public void run() { createGuiAndShow(); } }); }}package util;import java.awt.geom.Point2D;public class GeometryUtil { // 两点之间的距离 public static double distanceOfPoints(Point2D p1, Point2D p2) { double disX = p2.getX() - p1.getX(); double disY = p2.getY() - p1.getY(); double dis = Math.sqrt(disX * disX + disY * disY); return dis; } // 两点的中点 public static Point2D middlePoint(Point2D p1, Point2D p2) { double x = (p1.getX() + p2.getX()) / 2; double y = (p1.getY() + p2.getY()) / 2; return new Point2D.Double(x, y); } // 在两点所在直线上，以从startPoint到endPoint为方向，离startPoint的距离disToStartPoint的点 public static Point2D extentPoint(Point2D startPoint, Point2D endPoint, double disToStartPoint) { double disX = endPoint.getX() - startPoint.getX(); double disY = endPoint.getY() - startPoint.getY(); double dis = Math.sqrt(disX * disX + disY * disY); double sin = (endPoint.getY() - startPoint.getY()) / dis; double cos = (endPoint.getX() - startPoint.getX()) / dis; double deltaX = disToStartPoint * cos; double deltaY = disToStartPoint * sin; return new Point2D.Double(startPoint.getX() + deltaX, startPoint.getY() + deltaY); } // 绕原点的旋转矩阵，绕任意点旋转，可以先移动到原点，旋转，然后再移回去 // cosθ -sinθ 0 // sinθ +conθ 0 // 0000 +0000 1 // x = r*cosα, y = r*sinα // x' = r*cos(α+θ) = r*cosα*cosθ - r*sinα*sinθ = x*cosθ - y*sinθ // y' = r*sin(α+θ) = r*sinα*cosθ + r*cosα*sinθ = x*sinθ + y*cosθ // (x, y)绕圆心旋转degree度 public static Point2D rotate(double x, double y, double degree) { return rotate(x, y, 0, 0, degree); } // (x, y)绕(ox, oy)旋转degree度 public static Point2D rotate(double x, double y, double ox, double oy, double degree) { x -= ox; y -= oy; double cos = Math.cos(Math.toRadians(degree)); double sin = Math.sin(Math.toRadians(degree)); double temp = x * cos - y * sin; y = x * sin + y * cos; x = temp; return new Point2D.Double(x + ox, y + oy); } public static void main(String[] args) { Point2D p = rotate(50, 10, 10); System.out.println(p); p = rotate(100, 60, 50, 50, 10); System.out.println(p); }}import java.awt.geom.Point2D;import java.util.ArrayList;import java.util.List;import org.eclipse.swt.SWT;import org.eclipse.swt.events.PaintEvent;import org.eclipse.swt.events.PaintListener;import org.eclipse.swt.graphics.GC;import org.eclipse.swt.graphics.Image;import org.eclipse.swt.graphics.Rectangle;import org.eclipse.swt.graphics.Transform;import org.eclipse.swt.layout.FillLayout;import org.eclipse.swt.widgets.Canvas;import org.eclipse.swt.widgets.Display;import org.eclipse.swt.widgets.Shell;import util.GeometryUtil;public class GrowingSWT{ private final Shell shell; private final Canvas canvas; private List<Point2D> ps = new ArrayList<Point2D>(); private boolean stopped = false; Image image = null; int type = 1; private final Runnable timer = new Runnable() { public void run() { shell.getDisplay().timerExec(500, timer); grow(); canvas.redraw(); } }; GrowingSWT(final Display display) { shell = new Shell(display, SWT.DOUBLE_BUFFERED | SWT.SHELL_TRIM); shell.setLayout(new FillLayout()); canvas = new Canvas(shell, SWT.NULL); canvas.addPaintListener(new PaintListener() { public void paintControl(PaintEvent e) { long time = System.currentTimeMillis(); if (type == 1) { e.gc.drawImage(getBuffer(false), 0, 0); } else { render(e.gc); } time = System.currentTimeMillis() - time; if (time > 10) { System.out.println(time); } } }); ps.add(new Point2D.Double(0, 0)); ps.add(new Point2D.Double(800, 0)); display.timerExec(500, timer); } Image getBuffer( boolean withRefresh) { Rectangle bounds = canvas.getBounds(); if (image == null || !image.getBounds().equals(bounds)) { image = new Image(shell.getDisplay(), bounds); renderWithBuffer(image); } else if (withRefresh) { renderWithBuffer(image); } return image; } public void grow() { if (stopped) { return; } List<Point2D> temp = new ArrayList<Point2D>(); temp.add(ps.get(0)); for (int i = 0; i < ps.size() - 1; ++i) { Point2D p0 = ps.get(i); Point2D p4 = ps.get(i + 1); double len = GeometryUtil.distanceOfPoints(p0, p4); if (len < 0.1) { // 当线条长度小于1时，就停止再增长 System.out.println(ps.size()); shell.getDisplay().timerExec(-1, timer); return; } Point2D p1 = GeometryUtil.extentPoint(p0, p4, len / 3); Point2D p3 = GeometryUtil.extentPoint(p0, p4, len * 2 / 3); Point2D p2 = GeometryUtil.rotate(p3.getX(), p3.getY(), p1.getX(), p1.getY(), 60); temp.add(p1); temp.add(p2); temp.add(p3); temp.add(p4); } ps = null; ps = temp; temp = null; if (type == 1) { getBuffer(true); } } private void renderWithBuffer(Image image) { GC _gc = new GC(image); render(_gc); _gc.dispose(); } private void render(GC gc) { Display display = shell.getDisplay(); gc.setBackground(display.getSystemColor(SWT.COLOR_BLACK)); Rectangle bounds = canvas.getBounds(); gc.fillRectangle(bounds); gc.setAdvanced(true); gc.setAntialias(SWT.ON); Transform transform = new Transform(display); transform.translate(0, bounds.height - 20); gc.setTransform(transform); gc.setForeground(display.getSystemColor(SWT.COLOR_WHITE)); for (int i = 0; i < ps.size() - 1; ++i) { Point2D sp = ps.get(i); Point2D ep = ps.get(i + 1); gc.drawLine((int) sp.getX(), -(int) sp.getY(), (int) ep.getX(), -(int) ep.getY()); } } public static void main(String[] args) { Display display = Display.getDefault(); Shell shell = new GrowingSWT(display).shell; shell.setSize(800, 400); shell.open(); while (!shell.isDisposed()) { if (!display.readAndDispatch()) { display.sleep(); } } }}