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<title>csdn_Java Script与Java Applet的综合运用(一)</title>
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<td WIDTH="50%" bordercolor="#FFFFFF" CLASS="t1" bgcolor="#F0F0F0" align="center" nowrap>Java Script与Java Applet的综合运用(一)</td>
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<BR>首先我们编写一个Java Applet,就叫HelloWorld1好了(大家对HelloWorld一定不会陌生). <NOBR>
<P>import java.awt.*; </P>
<P>import java.applet.*; <BR>public class HelloWorld1 extends Applet <BR>{ <BR><FONT color=#ff6666><B>public</B> </FONT>String text="Hello World!";//请注意此处的public <BR>public void paint(Graphics g) <BR>{g.drawString(text,20,20);} <BR>}</NOBR> </P>
<P>编译通过后会生成HelloWorld1.class(别告诉我程序无法通过！如果编译出错请检查是否拼写有误。)
<P><NOBR><BR><html> <BR><head><title>例子</title></head> <BR><body> <BR><script language="JavaScript"> <BR><!-- <BR>function SetText() <BR>{ <BR>document.app.text="世界你好!"; <BR><B><FONT color=#ff6666>document.app.repaint();</FONT></B><FONT color=#000000>//也请注意此句.</FONT> <BR>} <BR>//--> <BR></script> <BR>Java Script与Java Applet的综合运用例一<br> <BR><applet code="HelloWorld1.class" width="100" height="28" <FONT color=#ff0000>name="app"</FONT>> <BR></applet> <BR><form> <BR><input type="button" value="请点击这里" onclick="SetText()"> <BR></form> <BR></body> <BR></html></NOBR> </P>
<P>用浏览器打开example.html会出现一个显示“Hello World!”的Java Applet以及一个按钮“请点击这里”。我们点一下按钮，你会发现“Hello World!”变成了“世界你好”。这说明Java Script已经成功的改变了HelloWorld1中text的内容。 </P>
<P>你也许会问在在HelloWorld1.java中为什么要在text前加public?? <BR>还有Java Script中那行："document.app.repaint();"是什么意思?? <BR> </P>
<P>是这样的:
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<LI>和C++一样,在Java中缺省状态下,对象的属性是private,要让Java Script访问到Java Applet中的对象,必须设置为public(包括函数、变量和类)。
<LI>前一句document.app.text="世界你好!"仅改变了text的值,要使它反映在浏览器上,必须要让HelloWorld1刷新它的显示,因此要调用HelloWorld1中的repaint()函数。你也许又要问了:我在HelloWorld1.java中并没有看到repaint()函数呀? HelloWorld1是Applet的子类，我们调用repaint()其实是调用类Applet中的repaint()函数。当然我们并不推荐在外部直接修改Applet内的变量，更安全的方法是提供public函数来读取和改变内部变量。 </LI></UL>
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