在Linux中运行jerky的Java Animation程序

Question

我在Ubuntu 14.4.1中编写了一个简单的Java动画程序.一个球在JPanel内移动.但在执行时,球在JPanel中变得非常生涩.这个问题一直持续到我在JPanel中移动鼠标为止.在JPanel内移动鼠标时,球的运动非常顺畅.应该说我在Windows 10中运行了这个程序,并没有出现问题.我的程序代码如下:

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

public class BouncingBall extends JPanel {
    Ball ball = new Ball();

    void startAnimation() {
        while( true ) {
            try {
                Thread.sleep( 25 );
                ball.go();
                repaint();
            } catch( InterruptedException e ) {}
        } // end while( true )
    } // end method startAnimation()

    protected void paintComponent( Graphics g ) {
        super.paintComponent( g );
        ball.draw( g );
    } // end method paintComponent


    // inner class Ball
    class Ball {
        int x;
        int y;
        int diameter = 10;
        int xSpeed = 100;
        int ySpeed = 70;

        void go() {
            x = x + (xSpeed*25)/1000;
            y = y + (ySpeed*25)/1000;

            int maxX = getWidth() - diameter;
            int maxY = getHeight() - diameter;
            if( x < 0 ) {
                // bounce at the left side
                x = 0;
                xSpeed = -xSpeed;
            } else if( x > maxX ) {
                // bounce at the right side
                x = maxX;
                xSpeed = -xSpeed;
            } else if( y < 0 ) {
                // bounce at the top side
                y = 0;
                ySpeed = -ySpeed;
            } else if( y > maxY ) {
                // bounce at the bottom size
                y = maxY;
                ySpeed = -ySpeed;
            } // end if-else block
        } // end method go()

        void draw( Graphics g ) {
            g.fillOval( x , y , diameter , diameter );
        } // end method draw
    } // end inner class Ball


    public static void main( String[] args ) {
        JFrame window = new JFrame();
        window.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );
        BouncingBall animation = new BouncingBall();
        animation.setPreferredSize( new Dimension( 500 , 500 ) );
        animation.setBackground( Color.white );
        window.add( animation );
        window.pack();
        window.setVisible( true );

        animation.startAnimation();
    } // end method main
} // end class BouncingBall

问题是什么？我是否必须更改Ubuntu中的某些设置？我还在paintComponent方法中添加了一些测试代码,如下所示:

protected void paintComponent( Graphics g ) {
    System.out.println( "paintComponent call number: " + counter );
    ++counter;
    super.printComponent( g );
    ball.draw( g );
}  

在类MovingBall中声明的变量计数器初始值为0.我观察到每秒paintComponent的调用次数远远超过JPanel的实际刷新率.

Answer 1

Windows中默认启用视频加速,但在Linux中默认不启用.(这已经存在多年了;我可以发誓这个默认值已经针对最近的Java版本进行了更改,但显然我错了.)

您可以启用OpenGL以获得加速的性能:

public static void main( String[] args ) {
    System.setProperty("sun.java2d.opengl", "true");

    JFrame window = new JFrame();

或者,您可以在命令行上设置属性:

java -Dsun.java2d.opengl=true BouncingBall