applet1.java

矩阵乘法的计算程序

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

/*Applet在浏览器环境中运行的Java程序代码,其安全机制P182
系统提供的Applet类属于一个从Panel派生出来的容器组件,一个
Applet程序类的对象就是一个容器(相当于一个框架),程序中的
所有内容都出现在该容器中(无需框架),P184.
将Applet程序嵌入到网页中,相当于在网页中插入一个该Applet程序对象.
VJ++为每个Applet程序生成一个Label组件*/
/*系统提供的Applet类预设了几个重要的方法,并在恰当的时机自动调用.
1.init()初始化方法,程序的入口点(最早的执行代码),
  程序执行时,自动且只调用一次该方法
2.start() P185
3.stop()  P185
4.paint(Graphics g)负责在Applet容器上文字输出与绘制图型,随
  init()方法的执行而自动调用
*/
/*Applet应用程序类可以根据需要设计适当的数据成员,并在上述方法中
加入恰当的功能代码(重写上述方法)
*/
public class Applet1 extends Applet
{
	String hw_text;//用户自定义数据
	static int stop_count,start_count;//用户自定义数据
	/**
	 * The entry point for the applet. 
	 */
	public void paint(Graphics g)
	{
		g.drawString(hw_text,25,50);
		g.drawString("start_count="+start_count,25,70);
		g.drawString("stop_count="+stop_count,25,90);
	}
	public void init()
	{
		initForm();
		hw_text="你好 世界!";
		usePageParams();//在程序中使用通过网页传递的参数(标题 背景色 前景色)

	}
	public void start()
	{
		start_count+=1;
		//paint(this.getGraphics()); 
	}
	public void stop()
	{
		stop_count+=1;
	}
					  
	private	final String labelParam = "label";
	private	final String backgroundParam = "background";
	private	final String foregroundParam = "foreground";

	/**
	 * Reads parameters from the applet's HTML host and sets applet
	 * properties.
	 */
	private void usePageParams()
	{
        //程序自设的(标题 背景色 前景色)
		final String defaultLabel = "Default label";
		final String defaultBackground = "C0C0C0";
		final String defaultForeground = "000000";
		String labelValue;
		String backgroundValue;
		String foregroundValue;

		/** 
		 * Read the <PARAM NAME="label" VALUE="some string">,
		 * <PARAM NAME="background" VALUE="rrggbb">,
		 * and <PARAM NAME="foreground" VALUE="rrggbb"> tags from
		 * the applet's HTML host.
		 */	
        //从网页中获取标题 背景色 前景色
		labelValue = getParameter(labelParam);
		backgroundValue = getParameter(backgroundParam);
		foregroundValue = getParameter(foregroundParam);

		if ((labelValue == null) || (backgroundValue == null) ||
			(foregroundValue == null))
		{
			/**
			 * There was something wrong with the HTML host tags.
			 * Generate default values.
			 */
			labelValue = defaultLabel;
			backgroundValue = defaultBackground;
			foregroundValue = defaultForeground;
		}

		/**
		 * Set the applet's string label, background color, and
		 * foreground colors.
		 */
		//设置Applet容器的标题 背景色 前景色
		label1.setText(labelValue);
		label1.setBackground(stringToColor(backgroundValue));
		label1.setForeground(stringToColor(foregroundValue));
		this.setBackground(stringToColor(backgroundValue));
		this.setForeground(stringToColor(foregroundValue));
	}

	/**
	 * Converts a string formatted as "rrggbb" to an awt.Color object
	 */
	private Color stringToColor(String paramValue)
	{
		int red;
		int green;
		int blue;

		red = (Integer.decode("0x" + paramValue.substring(0,2))).intValue();
		green = (Integer.decode("0x" + paramValue.substring(2,4))).intValue();
		blue = (Integer.decode("0x" + paramValue.substring(4,6))).intValue();

		return new Color(red,green,blue);
	}

	/**
	 * External interface used by design tools to show properties of an applet.
	 */
	//外部接口
	public String[][] getParameterInfo()
	{
		String[][] info =
		{
			{ labelParam, "String", "Label string to be displayed" },
			{ backgroundParam, "String", "Background color, format \"rrggbb\"" },
			{ foregroundParam, "String", "Foreground color, format \"rrggbb\"" },
		};
		return info;
	}

	Label label1 = new Label();

	/**
	 * Intializes values for the applet and its components
	 */
	//初使化Applet容器的窗体
	void initForm()
	{
		this.setBackground(Color.lightGray);
		this.setForeground(Color.black);
		label1.setText("label1");
		this.setLayout(new BorderLayout());//默认布局管理器为FlowLayout
		this.add("North",label1);
	}
}