如何从JavaScript调用applet方法 [英] How to call an applet method from JavaScript
问题描述
我已经创建了一个applet，并且我将从Web项目上的HTML页面访问applet方法.
I have created an applet and I am going to access an applet method from my HTML page on a web project.
这是我的applet的样子:
Here my applet looks like:
public class MessageApplet extends Applet {
private Label m_mess;
public void init()
{
setBackground(Color.lightGray);
setLayout(new BorderLayout());
m_mess = new Label("MessageApplet is Running...: No Selection Yet", Label.CENTER);
add(BorderLayout.CENTER, m_mess);
}
public void setMessage(String message)
{
m_mess.setText("Selection: " + message);
}
}
我的HTML页面如下:
And my HTML page looks like:
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Insert title here</title>
<SCRIPT LANGUAGE="JavaScript">
function selectedCity()
{
if(document.CityChoice.City[0].checked == true)
{
document.SimpleMessageApplet.setMessage(document.CityChoice.City[0].value);
}
}
</SCRIPT>
</HEAD>
<BODY>
<b>This is the applet</b>
<APPLET
CODE="MessageApplet.class"
NAME="SimpleMessageApplet"
WIDTH=350
HEIGHT=100>
</APPLET>
<FORM NAME="CityChoice">
<input type="radio" name="City" value="Boston" onClick="selectedCity()"> Boston<br>
</form>
</BODY>
</html>
但是，当我单击单选按钮时，浏览器将挂起，并且无法访问applet方法.
But when I click radio button my browser hangs and I cannot access the applet method ever.
我的applet类在默认目录中，而HTML在WebContent文件夹中.我应该更改我的代码吗?
My applet class is in default directory and HTML is in WebContent folder. What should I change in my code?
推荐答案
问题是if语句检查:
document.CityChoice.City[0].checked == true
这与JavaScript不完全一样，因为那里的错误表达式会引发错误，并且永远不会将其放入if语句主体中.
This is not exactly how it goes with JavaScript since the wrong expression you have there throws an error and it never makes it into the if statement body.
我删除了if语句，并将代码更改为如下内容:
I removed the if statement and changed the code to something like this:
function selectedCity()
{
document.SimpleMessageApplet.setMessage("Hello");
}
当我单击时，我会看到Hello消息很好.
When I click I see the Hello message fine.
将您的HTML文件内容更改为以下内容:
Change your HTML file content to something like:
<html><head><meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Insert title here</title>
<SCRIPT LANGUAGE="JavaScript">
function selectedCity()
{
var elem = document.getElementById('cityRb');
if(elem.checked)
{
document.SimpleMessageApplet.setMessage(elem.value);
}
}
</SCRIPT></HEAD>
<BODY >
<b>This is the Applet</b>
<APPLET CODE="MessageApplet.class" NAME="SimpleMessageApplet" WIDTH=350 HEIGHT=100 >
</APPLET >
<FORM NAME="CityChoice">
<input type="radio" id="cityRb" name="City" value="Boston" onClick="selectedCity()"> Boston<br>
</form>
</BODY >
</html>
还要添加完整的类代码:
Also adding the full class code:
import java.applet.Applet;
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Label;
/**
*
* @author hmmmmm
*/
public class MessageApplet extends Applet {
private Label m_mess;
public void init() {
setBackground(Color.lightGray);
setLayout(new BorderLayout());
m_mess = new Label("MessageApplet is Running...: No Selection Yet", Label.CENTER);
add(BorderLayout.CENTER, m_mess);
m_mess.setBackground(Color.red);
}
public void setMessage(String message) {
m_mess.setText("Selection: " + message);
}
}
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