Multiple event-handling threads?

I am writing a Java program that will launch other Java programs within the same JVM. This feature is for an RAD IDE that currently uses Runtime.exec.
The main problem is that the launcher is an IDE that will try to launch Swing applications within the same JVM. If a badly-written program traps the event-handling thread, it will bring the whole IDE down. The IDE's "Kill" button wont even work.
Is there any way to tell the JVM to use different event-handling threads for my application? Alternatively, does anybody know of any obscure functions I could use to maybe cause the event-handling thread to delegate processing to another one of my own threads? Ugly hacks are welcome.

After I first posted this question, I've taken a look at the java.awt.EventQueue class. The API provides an easy way to use your own EventQueue that could possibly dispatch events with multiple threads. If you make sure that you only use one thread at a time for each virtual JVM, I don't think that there will be any thread issues (unless there are any assumptions in AWT/Swing code about there only being one thread).
About the load time being 0.5 seconds. I'm sure it'll improve, but a failed load only loads and links a minimum number of classes. I wrote a program that runs the java compiler from com.sun.tools.javac.Main and it looks like the load time is about 1.75 seconds. Since the compile time itself is usually under a second for around 2000 lines of code, this kind of makes a difference (500MHz P3, by the way). This load time will probably be even greater for Swing applications.
When you're lauching a big program it may not matter much but the load time really kills Java's ability to create a quick command-line tool (not that it's best-suited for such a tool anyway, but it would be nice to have that barrier removed).
The biggest problem with creating a lightweight JVM right now is probably the stupid File class. Even if you change "user.dir" in the system properties, many File methods still resolve relative to the original "user.dir". Though many other problems exist, this is the one that really kills it because of the pervasiveness of the File class.

Similar Messages

Multiple Event Handler

Hey,
This is probably a really stupid question but is there a way
to declare an event handle on an Actions layer that handles
multiple events?
For example, both of these are equivalent:
// on button
on (rollOut)
// on action layer
btnTest.onRollOut = function()
// on button
on(rollOut, releaseOutside)
// on action layer

btnTest.onRollOut = btnTest.onReleaseOutside = function(){
}

Multiple events handled in a case, variant type newval

Hi!
I use an event case structure, and one case handles two value change events. One is a button's, the other is a cluster of controls'.
I would like to distinguish, whether the source was the button, or one of the controls in the cluster, but i get back the new-val and old-val in a variant type.
How could i get the appropriate values back?
Thanks
Solved!
Go to Solution.

For this, you would use the "ctlref" event terminal, not the "newval".
If you only have two controls, create a control reference for one and compare it with the ctlref event terminal. If they are equal, that was the control, else the other one. Place the terminal of both controls inside the event to get the values of each.
(If you have more than two controls, create an array of control references and use "search array" for the ctrlref output)
If your controls have unique names, you could also use the ctlref to get the control label, for example.
LabVIEW Champion . Do more with less code and in less time .

Multiple event handling

hi ,
Please can i have the soultion for the problem which i am facing.
My page is consists of the table where a single column is defined as MessageInputText.
The data is accepted int and validited by PPR on the InputText.( i.e either by tabbing out the inputtext or by clicking the mouse outside the text box. )
But in the rare senario when the user inputs the data and immediately clicks on the save or cancel button without tabbing out , the button functionality is not handled, as PPR is only activated.
Can i know how to make the system recoginize to handle both the events simultanously.
regards
lakshmi

Read "PPR Event Queuing" topic in PPR chapter of devguide.
This is what it has to say
PPR Event Queuing
By default, when a PPR event fires, all subsequent events on the page are ignored. So, for example, assume you have a text input field configured to fire a PPR event when the user leaves, and you also have a submit button on the page. The user makes a change to the data in the text input field, and then uses her mouse to select the submit button. In this case, the text field's PPR event fires and the button click is ignored.
If you want to change this behavior so the first event generated after the PPR event is processed immediately after the PPR event response is received (so the subsequent event is sent in a separate request), add the following code to your page's controller:
import oracle.apps.fnd.framework.webui.beans.OABodyBean;
import oracle.apps.fnd.framework.webui.OAWebBeanConstants;
public void processRequest(OAPageContext pageContext, OAWebBean webBean)
super.processRequest(pageContext, webBean);
OAWebBean body = pageContext.getRootWebBean();
if (body instanceof OABodyBean)
body.setAttributeValue(OAWebBeanConstants.FIRST_CLICK_PASSED_ATTR, Boolean.TRUE);
With this code, the button click described in the example above would no longer be ignored.
Thanks
Tapash

Using JOptionPane in a non-event dispatching thread

I am currently working on a screen that will need to called and displayed from a non-event dispatching thread. This dialog will also capture a user's selection and then use that information for later processing. Therefore, the dialog will need to halt the current thread until the user responds.
To start, I tried using the JOptionPane.showInputDialog() method and set the options to a couple of objects. JOptionPane worked as advertised. It placed the objects into a combobox and allowed the user to select one of them. However, it also gave me something unexpected. It actually paused the non-event handling thread until the user had made a selection. This was done without the JOptionPane code being wrapped in a SwingUtilities.invokeLater() or some other device that would force it to be launched from an Event Handling Thread.
Encouraged, I proceeded to use JOptionPane.showInputDialog() substituting the "message" Object with a fairly complex panel (JRadioButtons, JLists, JTextFields, etc.) that would display all of the variety of choices for the user. Now, when the screen pops up, it doesn't paint correctly (like what commonly occurs when try to perform a GUI update from a non-event dispatching thread) and the original thread continues without waiting for a user selection (which could be made if the screen painted correctly).
So, here come the questions:
1) Is what I am trying to do possible? Is it possible to create a fairly complex GUI panel and use it in one of the static JOptionPane.showXXXDialog() methods?
2) If I can't use JOptionPane for this, should I be able to use JDialog to perform the same type function?
3) If I can use JDialog or JFrame and get the threading done properly, how do I get the original thread to wait for the user to make a selection before proceeding?
I have been working with Java and Swing for about 7-8 years and have done some fairly complex GUIs, but for some reason, I am stumped here. Any help would be appreciated.
Thanks.

This seems wierd that it is functioning this way. Generally, this is what is supposed to happen. If you call a JOptionPane.show... from the Event Dispatch Thread, the JOptionPane will actually begin processing events that normally the Event Dispatch Thread would handle. It does this until the user selects on options.
If you call it from another thread, it uses the standard wait and notify.
It could be that you are using showInputDialog for this, try showMessageDialog and see if that works. I believe showInputDialog is generally used for a single JTextField and JLabel.

Custom event handling

Hi,
Please could someone help? I've been working my way through
the examples in the book 'essential guide to flex 2 and
actionscript 3.0'. When working through the example in chapter 10
I've been unable to get the custom CartEvent event of type
bookSelected to run.
I've stored the
small set of files in a
zip... please could someone tell me where I'm going wrong?
Thanks.
Craig

The most common definition for fireXXXEvent...public void fireXXXEvent(XXXEvent event) {
    synchronized (xxxListenerList) {
        Iterator i = xxxListenerList.iterator();
        while (i.hasNext()) {
            ((XXXListener) i.next()).xxx(event);
}Firing the event is simple. Firing the event in a dedicated event-handling thread (a-la AWT) is less simple - set up an event queue (a-la java.awt.EventQueue) to oversee the event handling thread.
Depending on your circumstances, chances are you won't need a separate thread. In fact, unless you specifically require multi-threading, things will be much simpler if you stick to a single thread.
There's nothing magical about events - it is simply a useful logical representation of a physical model.

Rather complicated (possibly!) threading/event handling problem...

OK, so here's a good question to ask for my first post to this site!
My current "project" is a GUI applet that does real-time interactions on a set of objects and user input. I'm using double buffering, event handling (from the keyboard) and multiple threads to handle the categories of "user input and graphics" and "world state updating." Here is a rough overview of how the program is layed out:
// keyboard input status class
class Keyboard extends KeyListener {
   static int[] code = new int[7];            // contains keycodes of interesting keys
   static boolean[] status = new boolean[7];     // status of keys (true=pressed)
   static boolean getStatus(int key) {
      return status[key];
   void keyPressed(KeyEvent e) {
      for(int i = 6; i >= 0; i--)
         if(code[i] == e.code)
            status[i] = true;
   void keyReleased(KeyEvent e) {
      for(int i = 6; i >= 0; i--)
         if(code[i] == e.code)
            status[i] = false;
// main program applet
class Program extends Applet implements Runnable {
   static Thread thread;      // main thread of applet
   static Image buffer;         // double buffer for offscreen rendering
   static boolean running; // flag to indicate status of applet
   void init() {
      buffer = createImage(500, 500);
      // other initializations
   void destroy() {
      // other disposes
   void start() {
      running = true;
      thread = new Thread(this);
      thread.start();
      addKeyListener(new Keyboard());   // begin receiving input
   void stop() {
      running = false;
      if(thread != Thread.currentThread())
         thread.join();    // wait for thread to die before continuing
   void run() {
      double paintTimer = 0;   // timer to suspend painting to buffer until necessary
      double dt = 0;       // difference in time between loops
      while(running) {
         // update timing stuff (dt and paintTimer)
         // update world status
         paintTimer -= dt;      // to decrement painting timer
         if(paintTimer <= 0) {
            paintTimer = 1.0 / fps;    // reset paint timer based on current fps setting
            synchronized(syncObject) {
               // paint world to buffer
               repaint();
         Thread.yield(); // to yield time to painting and user input thread
   // this method is only called by the internal thread within the applet
   // that is responsible for painting and event handling
   void paint(Graphics g) {
      // make sure painting to screen won't conflict with thread that's drawing on buffer!
      synchronized(syncObject) {
         g.drawImage(buffer, 0, 0, null); // do double buffering...paint buffer to screen
}So the end result is that it works fine some of the time, but every once in awhile I'll get these strange results where it'll seem as if the internal thread that handles graphics and input will get bogged down or stop responding normally, even with the Thread.yield() call from the main applet thread. I'll get results where the world will continue to be updated correctly, but the user input and onscreen rendering freeze in a particular state for a matter of seconds, and then it seems to regain control for a brief few milliseconds (hence I'll get a quick screen refresh and keyboard state change), and then it'll freeze again. Once this starts happening somewhere in the middle of execution, it continues to happen throughout that runtime session. Sometimes when I force-close the appletviewer I'll get weird native runtime exceptions that seem to occur within Sun's keyboard input manager.
Almost always it'll run perfectly for many minutes, and then all of a sudden it'll start to freeze up. Every once in awhile it freezes almost immediately after startup. I've run some testcases on it and am pretty confident it has nothing to do with the synchronization or the fact that I create a new applet thread every time the applet is restarted dynamically. Is it something happening within the event thread of the applet that I'm not aware of? Or is it something wrong with the flow of my code? Thanks for any input or help you can give! I'll be happy to send more details if needed.
Zach

right before your repaint, putSystem.out.println("Is EDT? "+SwingUtilities.isEventDispatcherThread());if its printing false, then you need to do SwingUtilities.invokeLater( ... );
and put GUI updating code in the invoke later.

How to use multiple Screen Event Handling on JavaFX

Hi,
Its appreciate , if any one assist me on Event Handling on JavaFX with multiple scene with single stage.
Thanks
Biswajit

I think is this usefull for you. . .
http://forums.sun.com/thread.jspa?threadID=5359128&tstart=30
Regards,
Rams.

Is it possible to handle multiple events using Jscript for a button in Apex

Hi,
I've application wherein in one of the pages for a button, I need to trigger 2 events as: 1. redirect to a new page upon 'click' of the button
2. display a set of values on 'mouse over' that button.
I'm able to handle both separately, but not in one button. I would like to know if there is any limitation in Apex that we cant handle multiple events? Currently I've put a text item near the button, and called the Jscript for mouse over event in that as a temporary workaround. Can someone let me know if this is feasible? If not any other alternative to handle this?
Thanks in advance,
gsachidh

Hi Gsachidh,
well interesting problem you're facinng. Indeed, it can't be specified using the 'Button Attributes' So we have to come up with an workaround.
A quick en dirty solution would be to specify it with the 'Optional URL Redirect options'. In a normal button, with processing on same page, this would be 'no target'. but in case of additional things to be done this can be used, using an target URL. I used this many times, in example with popUp windows for refreshing the caller object when changes are made. In your case we have to add next to the href an onmouseover event. this can be done with;
Target set to => URL
URL - target => javascript:doSubmit('<button_name>');" onMouseOver="javascript:showTooltip('tooltip');"
Here the " is the key, letting ApEx know the target (href) is doSubmit('<button_name>'), just like when no target would be specified and adding a new javascript event; onMouseOver.
Although this is a dirty solution in my opinion, it is the best i could come up with. I have another idea in how to do this, that is by adding this event dynamically with javascript with an addEvent. But i don't have an example at the moment for this scenario.
Simon
Message was edited by:
S1M0N

Beginners Questions about Multiple JPanels in JFrame and event handling

I am a newbie with SWING, and even a newerbie in Event Handling. So here goes.
I am writing a maze program. I am placing a maze JPanel (MazePanel) at the center of a JFrame, and a JPanel of buttons (ButtonPanel) on the SOUTH pane. I want the buttons to be able to re-randomize the maze, solve the maze, and also ouput statistics (for percolation theory purposes). I have the backbone all done already, I am just creating the GUI now. I am just figuring out EventHandlers and such through the tutorials, but I have a question. I am adding an ActionListener to the buttons which are on the ButtonPanel which are on JFrame (SOUTH) Panel. But who do I make the ActionListener--Basically the one doing the work when the button is pressed. Do I make the JFrame the ActionListener or the MazePanel the ActionListener. I need something which has access to the maze data (the backbone), and which can call the Maze.randomize() function. I'm trying to make a good design and not just slop too.
Also I was wondering if I do this
JButton.addActionListener(MazePanel), and lets say public MazePanel implments ActionListenerdoesn't adding this whole big object to another object (namely the button actionlistener) seem really inefficient? And how does something that is nested in a JPanel on JFrame x get information from something nested in another JPanel on a JFrame x.
Basically how is the Buttons going to talk to the maze when the maze is so far away?

I'm not an expert, but here's what I'd do....
You already have your business logic (the Maze classes), you said. I'm assuming you have some kind of public interface to this business logic. I would create a new class like "MazeGui" that extends JFrame, and then create the GUI using this class. Add buttons and panels as needed to get it to look the way you want. Then for each button that does a specific thing, add an anonymous ActionListener class to it and put whatever code you need inside the ActionListener that accesses the business logic classes and does what it needs to.
This is the idea, though my code is totally unchecked and won't compile:
import deadseasquirrels.mazestuff.*;
public class MazeGui extends JFrame {
JPanel buttonPanel = new JPanel();
JPanel mazePanel = new JPanel();
JButton randomizeB = new JButton();
JButton solveB = new JButton();
JButton statsB = new JButton();
// create instanc(es) of your Maze business logic class(es)
myMaze = new MazeClass();
// add the components to the MazeGui content pane
Component cp = getContentPane();
cp.add(); // this doesn't do anything, but in your code you'd add
            // all of your components to the MazeGui's contentpane
randomizeB.addActionListener(new ActionListener {
    void actionPerformed() {
      Maze newMaze = myMaze.getRandomMazeLayout();
      mazePanel.setContents(newMaze); // this is not a real method!
                                      // it's just to give you the idea
                                      // of how to manipulate the JPanel
                                      // representing your Maze diagram,
                                      // you will probably be changing a
                                      // subcomponent of the JPanel
solveB.addActionListener(new ActionListener {
    void actionPerformed() {
      Solution mySolution = myMaze.getSolution();
      mazePanel.setContents(mySolution); // again, this is not a real
                                         // method but it shows you how
                                         // the ActionListener can
                                         // access your GUI
// repeat with any other buttons you need
public static void main(String[] args) {
    MazeGui mg = new MazeGui();
    mg.setVisible(true);
    // etc...
}

Multiple JComboBox Event Handling Problem

Hi, guys
I am a newbie in Java. I need to create three JComboBox, say date, month and year and a JButton "submit". After I select the entries from the three JComboBox, I click the "search" button to display something in terms of the information I selected, but I have no idea how to write the actionPerformed( ActionEvent evt) to deal with the problem. Can anyone give me some hint?
Any help would be appreciated.

If you are asking how to write a basic event handler for when your button is pressed, RTM.
http://java.sun.com/docs/books/tutorial/uiswing/events/index.html

WPF UI running in seperate runspace - able to set/get controls via synchronized hash table, but referencing the control via the hash table from within an event handler causes both runspaces to hang.

I am trying to build a proof of concept where a WPF form is hosted in a seperate runspace and updates are handled from the primary shell/runspace. I have had some success thanks to a great article by Boe Prox, but I am having an issue I wanted to open up
to see if anyone had a suggestion.
My goals are as follows:
1.) Set control properties from the primary runspace (Completed)
2.) Get control properties from the primary runspace (Completed)
3.) Respond to WPF form events in the UI runspace from the primary runspace (Kind of broken).
I have the ability to read/write values to the form, but I am having difficulty with events. Specifically, I can fire and handle events, but the minute I try to reference the $SyncHash from within the event it appears to cause a blocking condition hanging both
runspaces. As a result, I am unable to update the form based on an event being fired by a control.
In the example below, the form is loaded and the following steps occur:
1.) Update-Combobox is called and it populates the combobox with a list of service names and selects the first item.
2.) update-textbox is called and sets the Text property of the textbox.
3.) The Text value of the textbox is read by the function read-textbox and output using write-host.
4.) An event handle is registered for the SelectionChanged event for the combobox to call the update-textbox function used earlier.
5.) If you change the selection on the combobox, the shell and UI hangs as soon as $SyncHash is referenced. I suspect this is causing some sort of blocking condition from multiple threads trying to access the synchronized nature of the hash table, but I am
unsure as to why / how to work around it. If you comment out the line "$SyncHash.TXT_Output.Dispatcher.Invoke("Send",[action]{$SyncHash.TXT_Output.Text = $Value})" within update-textbox the event handler will execute/complete.
$UI_JobScript =
try{
Function New-Form ([XML]$XAML_Form){
$XML_Node_Reader=(New-Object System.Xml.XmlNodeReader $XAML_Form)
[Windows.Markup.XamlReader]::Load($XML_Node_Reader)
try{
Add-Type –AssemblyName PresentationFramework
Add-Type –AssemblyName PresentationCore
Add-Type –AssemblyName WindowsBase
catch{
Throw "Unable to load the requisite Windows Presentation Foundation assemblies. Please verify that the .NET Framework 3.5 Service Pack 1 or later is installed on this system."
$Form = New-Form -XAML_Form $SyncHash.XAML_Form
$SyncHash.Form = $Form
$SyncHash.CMB_Services = $SyncHash.Form.FindName("CMB_Services")
$SyncHash.TXT_Output = $SyncHash.Form.FindName("TXT_Output")
$SyncHash.Form.ShowDialog() | Out-Null
$SyncHash.Error = $Error
catch{
write-host $_.Exception.Message
#End UI_JobScript
#Begin Main
add-type -AssemblyName WindowsBase
[XML]$XAML_Form = @"
<Window xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
<Window.Resources>
<DataTemplate x:Key="DTMPL_Name">
<TextBlock Text="{Binding Path=Name}" />
</DataTemplate>
</Window.Resources>
<DockPanel LastChildFill="True">
<StackPanel Orientation="Horizontal" DockPanel.Dock="Top">
<Label Name="LBL_Services" Content="Services:" />
<ComboBox Name="CMB_Services" ItemTemplate="{StaticResource DTMPL_Name}"/>
</StackPanel>
<TextBox Name="TXT_Output"/>
</DockPanel>
</Window>
$SyncHash = [hashtable]::Synchronized(@{})
$SyncHash.Add("XAML_Form",$XAML_Form)
$SyncHash.Add("InitialScript", $InitialScript)
$Normal = [System.Windows.Threading.DispatcherPriority]::Normal
$UI_Runspace =[RunspaceFactory]::CreateRunspace()
$UI_Runspace.ApartmentState = [System.Threading.ApartmentState]::STA
$UI_Runspace.ThreadOptions = [System.Management.Automation.Runspaces.PSThreadOptions]::ReuseThread
$UI_Runspace.Open()
$UI_Runspace.SessionStateProxy.SetVariable("SyncHash",$SyncHash)
$UI_Pipeline = [PowerShell]::Create()
$UI_Pipeline.Runspace=$UI_Runspace
$UI_Pipeline.AddScript($UI_JobScript) | out-Null
$Job = $UI_Pipeline.BeginInvoke()
$SyncHash.ServiceList = get-service | select name, status | Sort-Object -Property Name
Function Update-Combobox{
write-host "`nBegin Update-Combobox [$(get-date)]"
$SyncHash.CMB_Services.Dispatcher.Invoke($Normal,[action]{$SyncHash.CMB_Services.ItemsSource = $SyncHash.ServiceList})
$SyncHash.CMB_Services.Dispatcher.Invoke($Normal,[action]{$SyncHash.CMB_Services.SelectedIndex = 0})
write-host "`End Update-Combobox [$(get-date)]"
Function Update-Textbox([string]$Value){
write-host "`nBegin Update-Textbox [$(get-date)]"
$SyncHash.TXT_Output.Dispatcher.Invoke("Send",[action]{$SyncHash.TXT_Output.Text = $Value})
write-host "End Update-Textbox [$(get-date)]"
Function Read-Textbox(){
write-host "`nBegin Read-Textbox [$(get-date)]"
$SyncHash.TXT_Output.Dispatcher.Invoke($Normal,[action]{$Global:Return = $SyncHash.TXT_Output.Text})
$Global:Return
remove-variable -Name Return -scope Global
write-host "End Read-Textbox [$(get-date)]"
#Give the form some time to load in the other runspace
$MaxWaitCycles = 5
while (($SyncHash.Form.IsInitialized -eq $Null)-and ($MaxWaitCycles -gt 0)){
Start-Sleep -Milliseconds 200
$MaxWaitCycles--
Update-ComboBox
Update-Textbox -Value $("Initial Load: $(get-date)")
Write-Host "Value Read From Textbox: $(Read-TextBox)"
Register-ObjectEvent -InputObject $SyncHash.CMB_Services -EventName SelectionChanged -SourceIdentifier "CMB_Services.SelectionChanged" -action {Update-Textbox -Value $("From Selection Changed Event: $(get-date)")}

Thanks again for the responses. This may not be possible, but I thought I would throw it out there. I appreciate your help in looking into this.
To clarify the "Respond to control events in the main runspace"... I'm would like to have an event generated by a form object in the UI runspace (ex: combo box selectionchanged event) trigger a delegate within the main runspace and have that delegate in
the main runspace update the form in the UI runspace.
ex:
1.) User changes selection on combo box generating form event
2.) Event calls delegate (which I have gotten to work)
3.) Delegate does some basic processing (works)
4.) Delegate attempts to update form in UI runspace (hangs)
As to the delegates / which runspace they are running in. I see the $synchash variable if I run get-var within a delegate, but I do not see the $Form variable so I am assuming that they are in the main runspace. Do you agree with that assumption?

Applet UpCall from JS Event - Which Thread? Options

Hi,
With many direct references to the second lovely colour diagram on this
page: -
http://java.sun.com/javase/6/docs/technotes/guides/jweb/applet/applet...
I completely understand the hour-glass pause on the single-JS-thread
preservation architecture when the red arrow for the additional
"applet-spawned" thread tries to call down when the applet worker thread is
already calling down. Very clever; love it! Well done all involved.
What I'd like to know : -
1) When the additional applet-spawned thread calls down into Javascript and
that JS calls setTimeout(myFunc,1000) and myFunc eventually [up]Calls back
into the Applet, which thread will host the call to the applet method?
Default-Worker or Applet-Spawned? Is the tenuous link/association to a
round(ish)-trip preserved?
2) What happens when a single JAVA thread is the target of affection from
multiple Javascript UpCalls? (The scenario being a) an event upCalls to JAVA
b) The Applet takes some time before returning c) The single Javascript
thread is now free to accept further events or down-calls d) a subsequent
event has triggered another UpCall request e) but the thread is
busy/occupied with the first)
I am desperately trying to pin down architected behaviour here that is the
reciprocal of the down-call throttling. Please help if you can.
Cheers Richard Maher

Hi Baftos,
Thanks for your reply and help. Yes, anecdotally, UpCalls back to the Applet are handled by the thread that called down to Javascript. (As advertised and documented in the Round-Trip scenario). And the good news is that events that call back into the Applet (regardless of provenance) are handled by the appropriate "Applet N LiveConnect Worker Thread". So if you want to callback to the Applet Worker Thread then just setTimeout(yourFunc,0) rather than just yourFunc().
This is expected/wished-for behavior and it would be nice to see it documented somewhere? (The event-processing-thread" bit)
Now, if someone can answer part 2 of my question then that would be magnificent!
"> 1 Javascript UpCall" and "only one target Thread"
Cheers Richard Maher

*ACTUAL* event handling mechanism in java

Hi there! Could someone please help me find resources that explain how EXACTLY the event handling mechanism works in java?
My searches on google and java.sun take me to pages that explain how to code or something close to that. But what I actually want to know is how is all this handled BY Java- how does the event source or VM know how/when to fire and event? how the event is fired? how do objects keep track of the listener objects?...and all the background stuff like that.
I've downloaded the Java source code, too. But it seems like an ocean to me to wade through. Would be a great help if someone could 'point out the right path'.
Thank you very much!

Hi there! Could someone please help me find
resources that explain how EXACTLY the event
handling mechanism works in java?My counter question is why do you care how EXACTLY the mechanism works? It works, and that's all most people need to know.
How it works is an implementation issue, likely to change from release to release, or as more efficient mechanisms are discovered.
But what I actually want to know is how is all this
handled BY Java- how does the event source or VM
know how/when to fire and event?Native peers attached to a component (AWT) or the frame (Swing) notify Java that an event has occurred in some way. (This will likely change somewhat from platform to platform)
An AWTEvent is created to represent the native event (Swing requiring more overhead to locate the source of the event) which is added to the EventQueue.
how the event is fired? how do objects keep track of
the listener objects?...and all the background stuff like
that.The above is done on a native thread - not the event thread. The event thread is sitting in the event queue waiting for an event to come along. It processes events in the queue and sends them to the object which "generated" them. This object informs each of its listeners in turn about the event.
Objects keep track of listeners however they want. AWT objects seem to use java.awt.AWTEventMulticaster. Swing objects seem to use an javax.swing.event.EventListenerList. I tend to use multiple ArrayLists.
Note that native events are sent through the EventQueue because they originate from non-event-thread threads. Often when specialising events, in particular sending custom events in response to, say, a button press, the event firing will be done in-place, since it is already in the event thread. Custom events that originate from outside the event thread are customarily added to the EventQueue with EventQueue.invokeLater or invokeAndWait.
This is from inspection of the Java 1.3 source (specifically java.awt.Button and javax.swing.JComponent) and knowledge of the APIs.

Adobe plugin For Mouse Click Event Handler

Hi All, How to write plugin For Mouse Click Event Handler? Please reply quickly..
Thanks in Advance

AS has already been replied to you on the other threads.
THE ACROBAT SDK has all the information you need to implement your solution. If you investigate the SDK and find a specific part of implementing your solution that is causing a problem. Then post that specific problem on the forum so that Leonard/PDL/ Aandi/Everyone else, can help you with specific problems.
This question is too open ended for it to be easily answered with out doing a lot of work.
Please download the SDK.
Investigate the Documentation/Samples.
Start developing your plug-in. ( I would recommend the Acrobat-plug-in wizard)
And if you hit a specific problem we will be happy to try and help.
Please note MULTIPLE POSTS just annoy.
HTH
Malky

Multiple event-handling threads?

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