ch16l02.txt

《Web编程专家指南》

Listing 16.2 Dial class.

import java.awt.*;

class Dial extends Canvas implements Runnable
    {
    boolean flash;
    Thread timeThread;
    long sweepTime;
    long startTime;
    int ticksEvery, highEnd, lowEnd;
    String name;
    double percent;
    Color flashColor;

    public Dial(String aName, int aLowVal, int aHighVal, int aTicksEvery,
                long aSweepTime, Color fColor)
    {
        name = aName;
        lowEnd = aLowVal;
        highEnd = aHighVal;
        ticksEvery = aTicksEvery;
        flashColor = fColor;
        percent = .33333;
        sweepTime = aSweepTime;
        startTime = java.lang.System.currentTimeMillis();
        timeThread = new Thread(this);
        timeThread.setDaemon(true);
        timeThread.start();
    }

    public Dial()
    {
        startTime = java.lang.System.currentTimeMillis();
    }

    public void paint(Graphics g)
    {
        Rectangle myExtent = this.bounds();
        g.drawOval(0, 0, myExtent.width, myExtent.height);
        if(flash == true){
            g.setColor(flashColor);
            g.fillOval(0, 0, myExtent.width, myExtent.height);
            g.setColor(Color.black);
            g.drawString(name, 0, myExtent.height / 2);
            flash = false;
        }else{
            //convert percent done into an arc...
            int arcDegrees = (int) (percent * 360);
            g.fillArc(0, 0, myExtent.width, myExtent.height, 90, arcDegrees);
        }
    }

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

    public void run(){
        flash = false;
        while(true){
                long curTime = java.lang.System.currentTimeMillis();
                double oldPercent = percent;
                percent = (double)(curTime - startTime)/(double) sweepTime;
                percent -= (int) percent;
                if(percent < oldPercent){
                    //Cycle completed
                    flash = true;
                }
                repaint();
        }
    }

}