Event listener with one argument

Ruby JRuby
1

Hi,

I’m developing an app with JWT (JWt, Java Web Toolkit — Emweb) using
Jruby
1.6.3.
I have a problem adding a listener taking one argument:

I define a signal with one argument [1]:
@selection_clicked = Signal1.new(self)

and trigger it with one argument:
@selection_clicked.trigger(WImage.new(resource, “chart
coming…”))

I then inspect the instance of the signal and I’m adding a listener:
puts @lists.selection_clicked.inspect # prints
#Java::EuWebtoolkitJwt::Signal1:0x69127c4d
@lists.selection_clicked.add_listener(self) { |resource|
display_chart(resource) }

Below is the error I get, the null pointer exception being due to the
block
trying to access the argument.
The code works fine when using Listener1 and passing a block without
argument.
When using a Signal (with no argument), I have to modify the trigger
call
to remove the argument too, so the problem occurs when attaching the
listener.

Is my JRuby code to attach the listener correct?

Thanks in advance!

Raph

:1 warning: multiple values for a block parameter (0 for 1)
16191 [qtp555989664-18] ERROR eu.webtoolkit.jwt.WebSession - error
during
event handling: org.jruby.exceptions.RaiseException: Native Exception:
‘class java.lang.NullPointerException’; Message: null; StackTrace:
java.lang.NullPointerException
at
eu.webtoolkit.jwt.WContainerWidget.addWidget(WContainerWidget.java:304)

16192 [qtp555989664-18] ERROR eu.webtoolkit.jwt.WebSession - fatal
error:
org.jruby.exceptions.RaiseException: Native Exception: ‘class
java.lang.NullPointerException’; Message: null; StackTrace:
java.lang.NullPointerException
at
eu.webtoolkit.jwt.WContainerWidget.addWidget(WContainerWidget.java:304)

org.jruby.exceptions.RaiseException: Native Exception: ‘class
java.lang.NullPointerException’; Message: null; StackTrace:
java.lang.NullPointerException
at
eu.webtoolkit.jwt.WContainerWidget.addWidget(WContainerWidget.java:304)

    at

eu.webtoolkit.jwt.WContainerWidget.addWidget(WContainerWidget.java:304)
Caused by: java.lang.NullPointerException
… 1 more

[1]

2

Looking at this again, looking for your input:
Can someone confirm that the following JRuby code is the right
translation
(regarding the addition of the event listener) of the java code below?
The
java code gets the listener’s argument, the Jruby listener gets no
argument
value (e is nil…).

Ruby:
nameEdit = WLineEdit.new
nameEdit.keyPressed.addListener(self) do |e|
puts ‘---------------------------’
puts e.getKey().toString()
puts ‘---------------------------’
end

Java:
nameEdit.keyPressed().addListener(this, new
Signal1.Listener() {
public void trigger(WKeyEvent e) {
greeting.setText("Key pressed : " +
e.getKey().toString());
}
});

thanks

Raph

3

Hi Rapj, that (J)Ruby code of yours (with the event listener implemented
as a block) should have worked …

Maybe it’s a bug try a newer JRuby if you must use 1.6 than the latest
1.6.8 … it really should work.

K.

4

Interesting, than that’s either a bug and/or smt weird with JWT.
I’ve tried similar code with Swing and it is working as expected :

window = javax.swing.JDialog.new
=> #Java::JavaxSwing::JDialog:0x52847b05

window.add_property_change_listener(‘visible’) { |e| puts “property
visible changed: #{e}” }
=> nil

window.fire_property_change ‘visible’, true, false
property visible changed:
java.beans.PropertyChangeEvent[propertyName=visible; oldValue=true;
newValue=false; propagationId=null;
source=javax.swing.JDialog[dialog1,641,365,338x214,layout=java.awt.BorderLayout,MODELESS,title=Hello
There!,defaultCloseOperation=HIDE_ON_CLOSE,rootPane=javax.swing.JRootPane[,1,29,336x184,layout=javax.swing.JRootPane$RootLayout,alignmentX=0.0,alignmentY=0.0,border=,flags=16777673,maximumSize=,minimumSize=,preferredSize=],rootPaneCheckingEnabled=true]]
=> nil

K.

5

Hi Karol,

Thanks for your feedback!

I have tested again with this version of Jruby with the same result:
jruby 1.7.4 (1.9.3p392) 2013-05-16 2390d3b on OpenJDK 64-Bit Server VM
1.6.0_24-b24 [linux-amd64]

The output is:

17026 [qtp1272015198-18] ERROR eu.webtoolkit.jwt.WebSession - error
during
event handling: org.jruby.exceptions.RaiseException: (NoMethodError)
undefined method `getKey’ for nil:NilClass

6

Actually I see it now … there are multiple 2 argument addListener
methods on the API - it’s not picking the one you’re assuming.

You will need to help it to call the one you’d like … but than of
course
the Ruby code gets a bit ugly, adjust your code accordingly :

listener = Proc.new { |e| puts “property visible changed: #{e}” }
=> #Proc:0x496d5aa8@:50(irb)

listener = listener.to_java
java.beans.PropertyChangeListener.java_class.to_java
=> #Java::OrgJrubyGen::InterfaceImpl1904177314:0x6cd0b6f8

window.add_property_change_listener ‘visible’, listener
=> nil

Maybe there’s a simpler way to do this with JRuby … not sure.

K.

7

Thanks Karol, the following code works indeed:

nameEdit = WLineEdit.new
listener = Proc.new do |k|
  puts '---------------------------'
  puts k.getKey().toString()
  puts '---------------------------'
end
listener = listener.to_java Signal1::Listener.java_class.to_java
nameEdit.keyPressed.addListener(self, listener)
page_layout.addWidget(nameEdit)

Manuel, thanks for the links, I keep them at hand!

Raph

On Thu, Sep 12, 2013 at 11:44 PM, Manuel R. Caro <

8

Hi,

Events on Swing works fine. I dont know how works on JWT but looks
similar. Maybe you aren’t doing reference to the right class as Karol
said. Some heritage can do a easy readable code for you …

Look at this Jslider example on Swing…

http://zetcode.com/gui/jrubyswing/components/

I’m developing on free time an Jruby Swing GUI and make use of a lot of
events on that way.

Regards.