buffercanvas.java

演示win32的socket 通讯 八皇后的改进算法 并发Concurrency的JAVA实现 applet演示鼠标的点击时间和显示图象 手机J2ME的多线程演示

/*
@author  j.n.magee 20/04/98
*/
package concurrency.buffer;

import java.awt.*;
import java.applet.*;


/**************************************************************/

class BufferCanvas extends Canvas {
    String title_;
    int slots_;
    int in_=0;
    int out_=0;
    char[] buf_ = {' ',' ',' ',' ',' '};

    Font f1 = new Font("Helvetica",Font.ITALIC+Font.BOLD,24);
    Font f2 = new Font("TimesRoman",Font.BOLD,36);

    BufferCanvas(String title, int slots) {
        super();
        title_=title;
        slots_=slots;
        resize(20+50*slots_,150);
        setBackground(Color.cyan);
  	}

    public void setvalue(char[] buf,int in, int out){
        buf_=buf;
        in_=in;
        out_=out;
        repaint();
    }

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

    Image offscreen;
    Dimension offscreensize;
    Graphics offgraphics;

    public synchronized void update(Graphics g){
        Dimension d = size();
	    if ((offscreen == null) || (d.width != offscreensize.width)
	                            || (d.height != offscreensize.height)) {
	        offscreen = createImage(d.width, d.height);
	        offscreensize = d;
	        offgraphics = offscreen.getGraphics();
	        offgraphics.setFont(getFont());
	    }

	    offgraphics.setColor(getBackground());
	    offgraphics.fillRect(0, 0, d.width, d.height);

         // Display the title
        offgraphics.setColor(Color.black);
        offgraphics.setFont(f1);
        FontMetrics fm = offgraphics.getFontMetrics();
        int w = fm.stringWidth(title_);
        int h = fm.getHeight();
        int x = (size().width - w)/2;
        int y = h;
        offgraphics.drawString(title_, x, y);
        offgraphics.drawLine(x,y+3,x+w,y+3);
        // Buffer Boxes
        y = size().height/2 - 15;
        offgraphics.setColor(Color.white);
        offgraphics.fillRect(10,y,50*slots_,50);
        offgraphics.setColor(Color.black);
        offgraphics.setFont(f2);
        for(int i=0; i<slots_; i++) {
            offgraphics.drawRect(10+50*i,y,50,50);
            offgraphics.drawChars(buf_,i,1,25+50*i,y+35);
        }
        //Input and output Pointers
        offgraphics.setColor(Color.blue);
        offgraphics.fillOval(35+50*in_,y-20,15,15);
        offgraphics.setColor(Color.yellow);
        offgraphics.fillOval(35+50*out_,y+55,15,15);
        g.drawImage(offscreen, 0, 0, null);
    }
}


/**************************************************************/