java - Swing主动渲染效率或如何将主动渲染与gui widgets结合起来

Question

继续 previous question ，我一直在寻找将主动渲染与 Java 中的文本字段相结合的最佳方式。我尝试了几种选择，使用 BufferStrategy、VolatileImage 或在标准 AWT 中覆盖 update() 和 paint()，但我最终使用了 Swing。

我在这里发布当前的状态，以防万一有人根据我的代码示例有新的见解，也许其他正在开发类似应用程序的人可能会从我的发现中受益。

目标是完成这三个壮举:

• 在仅在必要时更新的背景缓冲区之上呈现动画对象
• 在渲染结果之上使用文本框
• 毫无问题地调整窗口大小

下面是在stackoverflower的大力帮助下开发的演示应用程序的代码trashgod .
两个注意事项:

1) 严格刷新动画中前一步无效的区域似乎很容易出现视觉错误，因此我放弃了。这意味着我现在每帧都重新绘制整个背景缓冲区。

2) 将 BufferedImage 绘制到屏幕上的效率在很大程度上取决于平台。 Mac 实现似乎没有正确支持硬件加速，这使得将背景图像重新绘制到输出窗口成为一项繁琐的任务，当然这取决于窗口的大小。

我在我的 2.93 GHz 双核 iMac 上发现了以下结果:

Mac 操作系统 10.5:
640 x 480:0.9 毫秒，8 - 9%
1920 x 1100:5 毫秒，35 - 40%

Windows XP:
640 x 480:0.05 毫秒，0%
1920 x 1100:0.05 毫秒，0%

图例:
屏幕大小:绘制一帧的平均时间、应用程序的 CPU 使用率。

据我所知，下面的代码是实现我的目标的最有效方式。非常欢迎任何新的见解、优化或测试结果!

问候，马蒂斯

import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.GraphicsConfiguration;
import java.awt.GraphicsDevice;
import java.awt.GraphicsEnvironment;
import java.awt.GridLayout;
import java.awt.Rectangle;
import java.awt.Transparency;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.ComponentAdapter;
import java.awt.event.ComponentEvent;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.image.BufferedImage;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTextField;
import javax.swing.Timer;

public class SwingTest extends JPanel implements 
 ActionListener, 
 Runnable 
{
 private static final long serialVersionUID = 1L;

 private BufferedImage backgroundBuffer;
    private boolean repaintbackground = true;

    private static final int initWidth = 640;
    private static final int initHeight = 480;
    private static final int radius = 25;
    private final Timer t = new Timer(20, this);
    private final Rectangle rect = new Rectangle(); 

    private long totalTime = 0;
    private int frames = 0;
    private long avgTime = 0;

    public static void main(String[] args) {
        EventQueue.invokeLater(new SwingTest());
    }

    public SwingTest() {
        super(true);
        this.setPreferredSize(new Dimension(initWidth, initHeight));
        this.setLayout(null);
        this.setOpaque(false);
        this.addMouseListener(new MouseHandler());
    }

    @Override
    public void run() {
        JFrame f = new JFrame("SwingTest");
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.addComponentListener(new ResizeHandler());

/*      This extra Panel with GridLayout is necessary to make sure 
   our content panel is properly resized with the window.*/
        JPanel p = new JPanel(new GridLayout()); 
        p.add(this);
        f.add(p);
        f.pack();
        f.setLocationRelativeTo(null);
        f.setVisible(true);

        createBuffer();     
        t.start();
    }    

    @Override
    public void actionPerformed(ActionEvent e) {
        this.repaint();
    }    

    @Override
    protected void paintComponent(Graphics g) {
     long start = System.nanoTime();
     super.paintComponent(g);

     if (backgroundBuffer == null) createBuffer();
     if (repaintbackground) {

/*   Repainting the background may require complex rendering operations, 
   so we don't want to do this every frame.*/       
      repaintBackground(backgroundBuffer);
            repaintbackground = false;
     }

/*  Repainting the pre-rendered background buffer every frame
       seems unavoidable. Previous attempts to keep track of the 
       invalidated area and repaint only that part of the background buffer 
       image have failed. */
     g.drawImage(backgroundBuffer, 0, 0, null);
     repaintBall(g, backgroundBuffer, this.getWidth(), this.getHeight());
     repaintDrawTime(g, System.nanoTime() - start);
    }

    void repaintBackground(BufferedImage buffer) {    
     Graphics2D g = buffer.createGraphics();
  int width = buffer.getWidth();
  int height = buffer.getHeight();

  g.clearRect(0, 0, width, height);
  for (int i = 0; i < 100; i++) {
   g.setColor(new Color(0, 128, 0, 100));
   g.drawLine(width, height, (int)(Math.random() * (width - 1)), (int)(Math.random() * (height - 1)));
  }
    }

    void repaintBall(Graphics g, BufferedImage backBuffer, int width, int height) {
     double time = 2* Math.PI * (System.currentTimeMillis() % 3300) / 3300.;
        rect.setRect((int)(Math.sin(time) * width/3 + width/2 - radius), (int)(Math.cos(time) * height/3 + height/2) - radius, radius * 2, radius * 2);

        g.setColor(Color.BLUE);
        g.fillOval(rect.x, rect.y, rect.width, rect.height);
    }

    void repaintDrawTime(Graphics g, long frameTime) {
     if (frames == 32) {avgTime = totalTime/32; totalTime = 0; frames = 0;}
     else {totalTime += frameTime; ++frames; }
     g.setColor(Color.white);
     String s = String.valueOf(avgTime / 1000000d + " ms");
        g.drawString(s, 5, 16);
    }

    void createBuffer() {
        int width = this.getWidth();
        int height = this.getHeight();

        GraphicsEnvironment ge = GraphicsEnvironment.getLocalGraphicsEnvironment();
        GraphicsDevice gs = ge.getDefaultScreenDevice();
        GraphicsConfiguration gc = gs.getDefaultConfiguration();
        backgroundBuffer = gc.createCompatibleImage(width, height, Transparency.OPAQUE);        

        repaintbackground = true;
    }    

    private class MouseHandler extends MouseAdapter {

        @Override
        public void mousePressed(MouseEvent e) {
            super.mousePressed(e);
            JTextField field = new JTextField("test");
            Dimension d = field.getPreferredSize();
            field.setBounds(e.getX(), e.getY(), d.width, d.height);
            add(field);
        }
    }

    private class ResizeHandler extends ComponentAdapter {

     @Override
     public void componentResized(ComponentEvent e) {
      super.componentResized(e);
      System.out.println("Resized to " + getWidth() + " x " + getHeight());
      createBuffer();
     }    
    }
}

Answer 1

我有几点看法:

1. 您改进的repaintDrawTime() 可读性很强，但它是micro-benchmark并受制于vagaries主机操作系统。我不禁想知道 XP 结果是否是该系统 limited clock resolution 的产物.我在 Windows 7 和 Ubuntu 10 上看到非常不同的结果。

2. 如果您不使用空布局，则不需要额外的面板； JPanel 的默认布局是 FlowLayout，f.add(this) 只是将它添加到框架默认的 BorderLayout 的中心.

3. 重复调用构造函数可能很耗时。

   考虑更换

   g.setColor(new Color(0, 128, 0, 100));
   

   与

   private static final Color color = new Color(0, 128, 0, 100);
   ...
   g.setColor(color);
   

   或者，一个简单的 color lookup table , 可能会有用，例如

   private final Queue<Color> clut = new LinkedList<Color>();