temp.java

美国Silab公司的CP2200网络芯片的编程范例

import java.applet.Applet;
import java.applet.AppletStub;
import java.awt.Graphics;
import java.awt.*;
import java.net.*;
import java.io.*;
import java.util.*;



public class Temp extends Applet {

	Update timer;
	public String temperature_str = "0.0";
	public Font font1,font2,font3;
    final int maxNumValues = 15;
	double values[] = new double[maxNumValues];
	int time[] = new int[maxNumValues];
	int i = 0;								// counting variable

	double tempHigh = 76.0;
	double tempLow = 74.0;
	boolean first_time = true;
//----------------------------------------------------------------------------------
//	Overridden applet functions (starting point of execution)
//----------------------------------------------------------------------------------
	public void init() {
		font1 = new Font("sans-serif", Font.BOLD, 34);
   		font2 = new Font("sans-serif", Font.BOLD, 20);
   		font3 = new Font("sans-serif", Font.BOLD, 10);
		setBackground(Color.blue);
		for(i = 0; i < maxNumValues; i++){
			values[i] = 1000;
			time[i] = (i + 1) - maxNumValues;
		}
	}
	public void start(){
  		timer = new Update();
  		timer.start();

 	}

	public void paint(Graphics g) {
    	drawText(g);
        drawAxis(g);
    }
    public void stop(){	
		timer.stop();    
	}
//----------------------------------------------------------------------------------
//	Nested Class Definitions
//----------------------------------------------------------------------------------
	class Update extends Thread {
	    public Update(){

	    }

		public void run() {
	       while(true){
	       setTemperature();
	       repaint();
	       try{
	         sleep(500);
	    }catch(InterruptedException e){

		   System.out.println("EXEPTION -- cannot sleep");
	    }
	   }
	  }
	 }

//----------------------------------------------------------------------------------
//	Member functions
//----------------------------------------------------------------------------------
	public void setTemperature(){

		URL u;
    	URLConnection uc;

    	try {
      		u = new URL("http://" + getDocumentBase().getHost() + "/get_data?arg=nothing");
      		try {

        		uc = u.openConnection();

        		System.out.println("Connecting...");
        		uc.connect();
				System.out.println("Connected...");

				BufferedReader in = new BufferedReader(
        							new InputStreamReader(uc.getInputStream()) );

        		System.out.println("Reading a line ...");
        		temperature_str =  in.readLine();
        		System.out.println("the line says: " + temperature_str);
        		in.close();
				System.out.println("The input stream buffer is closed \n-- EXECUTION OK");


				// increment the time
				for(i = 0; i < maxNumValues; i++){
					time[i]++;
				}
				// shift the values to the left
				for(i = 0; i < (maxNumValues - 1); i++){
					values[i] = values[i+1];
				}

				// store the new value in the last element of the array
				String temp_str1 =  temperature_str.substring(0, temperature_str.indexOf('.'));
				String temp_str2 =  temperature_str.substring(temperature_str.indexOf('.')+ 1);

				values[maxNumValues - 1] = Integer.valueOf(temp_str1).floatValue()
						+ (Integer.valueOf(temp_str2).floatValue()) / (float)10.0;

			 	// auto scale
			 	double val = values[maxNumValues - 1];

			 	if(first_time){ //check for first time through
				 	tempHigh =(double)((int) val + 1);
				 	tempLow =(double)((int) val - 1);
				 	first_time = false;
			 	}else{
				 	if( val >= tempHigh){
					 	tempHigh = (double)((int)(val + 1));
				    }
				    if( val <= tempLow){
					 	tempLow = (double)((int)(val - 1));
				    }
				}

      		} catch (IOException e) {
        		System.err.println(e);
      			temperature_str = "***";
        	} // end try catch
    	} catch (MalformedURLException e) {
      	System.err.println(e);
      	temperature_str = "***";
    	}// end try catch
	}// end set temperature

//----------------------------------------------------------------------------------
//	Drawing functions
//----------------------------------------------------------------------------------
	public void drawText(Graphics g){
		g.setFont(font1);
    	g.setColor(Color.red);
        g.drawString(temperature_str, 250, 34);
    }

 public void drawAxis(Graphics g){

		g.setColor(Color.yellow);
		g.setFont(font3);

		// Chart box parameters
		final int x0 = 50, y0 = 50;					// absolute orgin of chart
		final int xlen = 500, ylen = 250;             // length of drawing plane

		int ybot = y0 + ylen, xend = x0 + xlen; // maximum x and y values
	    int i = 0;								// counting variable

	    //Draw the x and y axis
	    g.drawLine(x0, y0, x0, ybot); 		 	// y-axis
		g.drawLine(x0, ybot, xend, ybot);   	// x-axis

		// Y-axis Label Parameters
		int numTicksY = 10;

		int x = x0 - 35; // start drawing axis labels 35 px to the left of the axis
		int y = ybot;	 // start drawing labels from the bottom (minimum value first)

		// Draw the Y-axis Labels -- upon entry, brush location x and y (left and top)
		// are initialized as offsets from (0,0) the top left corner of the window.
		double yLabelVal = tempLow;
		String label = "0.00";
		int lbl_len;
		for(i = 0; i <= numTicksY; i++){
			// determine the length of the label
			if(yLabelVal > 0 && yLabelVal < 10 ){
				lbl_len = 3;
			}else if ( yLabelVal == 0.0){
				lbl_len = 1;
			}else if (yLabelVal >= 100.0){
				lbl_len = 5;
			}else {
				lbl_len = 4;
			}

			label = String.valueOf(yLabelVal).substring(0, lbl_len); //convert from float->string and truncate
			g.drawString(label, x, y);							 //draw the label at(x,y)
			yLabelVal += (double)(tempHigh - tempLow)/numTicksY; //increment temperature by one tick's worth
			y -= ylen/numTicksY;						 		 //move the brush up one tick
		}

		// Draw Bars and Labels on the X-axis
		int barWidth = xlen / maxNumValues;
		double PixPerDegree = (double) ylen / (double)(tempHigh - tempLow);  //pixels per degree
		int xLabelVal;
		x = x0;
		y = ybot + 20;								//draw labels 20px below the axis

		for(i = 0; i < maxNumValues; i++){
			if(time[i] > 0){
		    	//write the label
				xLabelVal = time[i];
				label = String.valueOf(xLabelVal);
				g.drawString(label, x, y);

				// draw the bar
				double barHeightRatio = (values[i] - tempLow) / (tempHigh - tempLow);
				int barHeight = (int)( (double)ylen * barHeightRatio);
				g.fillRect(x, ybot - barHeight, barWidth, barHeight); //x,y,width,height
			}
			x = x + barWidth;
		}// end for
	}//end draw axis


} //end Temp class