Subj : Re: Implementing Java Interfaces NOT using Rhino
To   : Brendan Eich
From : Keno Albrecht
Date : Wed Jul 14 2004 11:15 pm

Hm, I see what you mean, but if I try the following example, I get the 
error "There is no Java method javax.swing.JButton.addActionListener 
that matches JavaScript argument types (object). Candidate methods with 
the same name are: void addActionListener(java.awt.event.ActionListener)

var actionListener = {
   actionPerformed: function() {
     java.lang.System.out.println("Say Cheese");
   }
}

var frame = new Packages.javax.swing.JFrame();
var button = new Packages.javax.swing.JButton("No Cheese, Gromit");
button.addActionListener(actionListener);
frame.getContentPane().add(button);
frame.setVisible(true);

Do I have to cast the "actionListener" (how?) before passing it to 
addActionListener? Something else wrong :-)?

Thanks,
Keno


Brendan Eich wrote:

> Keno Albrecht wrote:
> 
>> // create an array enumeration.
>> var elements = new Enumeration() {
>>    index: 0, elements: array,
>>    hasMoreElements: function() {
>>       return (this.index < this.elements.length);
>>    },
>>    nextElement: function() {
>>       return this.elements[this.index++];
>>    }
>> };
>>
> 
> That's not JavaScript, not ECMA-262.  You can't just write an object 
> initialiser after a new Foo() expression.
> 
> 
>> exits with "missing ; before statement" (pointing to "new 
>> Enumeration() }",
> 
> 
> 
> Good, that's the right error message.
> 
> 
>> while
>>
>> // create an array enumeration.
>> var elements = new Enumeration( {
>>    index: 0, elements: array,
>>    hasMoreElements: function() {
>>       return (this.index < this.elements.length);
>>    },
>>    nextElement: function() {
>>       return this.elements[this.index++];
>>    }
>> });
>>
>> (different braces!) fails with "Java class java.utils.Enumeration is 
>> abstract and therefore may not be instantiated" :-(.
> 
> 
> 
> All you want is an object that has the right properties to match the 
> interface.  You wrote that, in both examples above, when you wrote the 
> object initialiser.  So you just need to pass that off to Java as if it 
> were a java.util.Enumeration.
> 
> Here's where you need a LiveConnect guru.  Cc'ing some.
> 
> /be
> 
>>
>>
>> Well, since this is a really useful feature, I would like to use it 
>> within my code. Any comments?
>>
>> Thanks,
>> Keno

.