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<title>csdn_Java Script与Java Applet的综合运用(二)</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(二)</td>
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上次我们介绍了使用Java Script改变Java Applet中的变量的方法(严格来讲应该是改变了String类,不过可以简单的把String类看成是变量)； 我们说直接在Java Script中改变Java Applet中的变量是不可取的(至少是不推荐的)。 因为Java Applet本身并不知道变量被改变， 这会给Applet程序带来隐患(还记得我们不得不调用repaint()函数来刷新显示吗?)。 更为积极的做法是在Java Applet中提供public函数支持对内部对象的存取。下面我们对HelloWorld1.java和example.html进行改进,介绍如何在Java Script中调用Java Applet的函数： <BR>考虑到浏览器对同名的Java Applet往往使用cache,因此我们把程序命名为HelloWorld2.java
<P><NOBR>import java.awt.*; <BR>import java.applet.*; <BR>public class <FONT color=#ff0000>HelloWorld2</FONT> extends Applet<FONT color=#3333ff>//主类名必须与文件名相同</FONT> <BR>{ <BR>String text="Hello World!";<FONT color=#3333ff>//去掉text的public属性</FONT> <BR>public void paint(Graphics g) <BR>{g.drawString(text,20,20);} </P>
<P><FONT color=#3333ff>//这里增加一个public函数</FONT> <BR><B><FONT color=#ff6666>public</FONT></B> void SetString(String NewString) <BR>{ <BR>text=NewString; <BR>repaint();<FONT color=#3333ff>//自动调用repaint()函数</FONT> <BR>} </P>
<P>}</NOBR> <BR> </P>
<P>编译后生成HelloWorld2.class；
<P><NOBR><html> </P>
<P><head><title>例子</title></head> <BR><body> <BR><script language="JavaScript"> <BR><!-- <BR>function SetText() <BR>{ <BR>document.app.SetString("世界你好!"); <BR><FONT color=#3333ff>//这里不再需要repaint()函数了</FONT> <BR>} <BR>//--> <BR></script> <BR>Java Script与Java Applet的综合运用例二<br> <BR><applet code="<FONT color=#ff0000>HelloWorld2</FONT>.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>同样打开example2.html点击按钮后你会发现"Hello World!"变成了"世界你好!"，说明调用函数成功? </P>
<p align=right><a href="71.html" tppabs="http://www.chinajavaworld.com/doc/lang/71.html"></a></p>
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