Java小程序:调用JavaScript - JSObject.getWindow(本)始终返回null [英] Java Applet: Call JavaScript - JSObject.getWindow(this) returns always null
问题描述
我的Java Applet
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.File;
import javax.swing.JApplet;
import javax.swing.JButton;
import netscape.javascript.JSObject;
@SuppressWarnings("serial")
public class LocalFileSystem extends JApplet {
private JSObject js;
private final JButton button;
public LocalFileSystem() {
setLayout(null);
button = new JButton("getDrives()");
button.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent arg0) {
button.setText( getDrives() );
}
});
button.setBounds(25, 72, 89, 23);
add(button);
}
public void init() {
js = JSObject.getWindow(this);
}
public String getDrives() {
if (js != null) return "NULL";
for (File f: File.listRoots())
js.call("addDrive", new String[] { f.getAbsolutePath() });
return "NOT NULL";
}
}
我的HTML code:
<!-- language: lang-html --><html>
<head>
<script type="text/javascript"
src="https://ajax.googleapis.com/ajax/libs/jquery/1.6.1/jquery.min.js"></script>
</head>
<body>
<script type="text/javascript">
function addDrive(s) {
alert(s);
}
</script>
<object type="application/x-java-applet;version=1.4.1" width="180"
height="180" name="jsap" id="applet">
<param name="archive" value="http://localhost/LocalFileSystemApplet/bin/applet.jar?v=<?php print mt_rand().time(); ?>">
<param name="code" value="LocalFileSystem.class">
<param name="mayscript" value="yes">
<param name="scriptable" value="true">
<param name="name" value="jsapplet">
</object>
</body>
</html>
该小程序被加载,当我打的按钮,我总是getDrives得到NULL()返回。
为什么呢?
The applet is being loaded and when I hit the button I always get NULL returned by getDrives(). Why?
推荐答案
从模糊的记忆,来电以确定是否从 JSObject
将失败>的init()方法。
From vague memory, calls to establish the JSObject
will fail if called from the init()
method.
所以这个..
public void init() {
js = JSObject.getWindow(this);
}
..也许应该..
public void start() {
js = JSObject.getWindow(this);
}
由于的start()
方法可能会被调用多次(例如,从最小化恢复浏览器),它可能会付费使用支票:
Since the start()
method might be called many times (e.g. restoring the browser from minimized), it might pay to use a check:
public void start() {
if (js==null) {
js = JSObject.getWindow(this);
}
}
更新
我看到它在阅读从Java /写HTML字段值。 小印在页面的底部指出:
Update
I saw it in Read/Write HTML field values from JAVA. The 'small print' at the bottom of the page notes:
为达到最佳效果,从不使用LiveConnect的JSObject在applet的init()方法。
For best result, never use LiveConnect JSObject in Applet's init() method.
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