Java Applet: Call JavaScript - JSObject.getWindow(this) returns always null
My 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";
}
}
My 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"开发者_如何学Python>
<param name="name" value="jsapplet">
</object>
</body>
</html>
The applet is being loaded and when I hit the button I always get NULL returned by getDrives(). Why?
From vague memory, calls to establish the JSObject will fail if called from the init() method.
So this..
public void init() {
js = JSObject.getWindow(this);
}
..should probably be ..
public void start() {
js = JSObject.getWindow(this);
}
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);
}
}
Update
I saw it in Read/Write HTML field values from JAVA. The 'small print' at the bottom of the page notes:
For best result, never use LiveConnect JSObject in Applet's init() method.
Check this line of code:
if (js != null) return "NULL";
Shouldn't that be?:
if (js == null) return "NULL";
加载中,请稍侯......
精彩评论