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How to choose an AWT-EventQueue thread, when there are several of them

由 寵の児 提交于 2019-12-05 01:36:56

After a lot of experimentation and google searches with keywords like EventQueue and ThreadGroup I have finally found a solution (in the Works For Me category, mind you).

I use the sun.awt.AppContext class. Some documentation and sources here (grepcode.com)

  1. Get a Collection of the running AppContext's using the getAppContexts method.
  2. For each retrieved AppContext, get his ThreadGroup using the getThreadGroup method.
  3. With the ThreadGroup object, Use the getName method.
  4. When the name of the Thread Group starts with the http: address of your Forms Application, retrieve the Object property with key name sun.awt.AppContext.EVENT_QUEUE_KEY, using the get method of AppContext.
  5. The retrieved object is an EventQueue. Create an java.awt.event.InvocationEvent object, passing your Runnable to the CTOR, and use the postEvent method of EventQueue.
  6. Your run method will be executed in the right thread.

Remarks:

  • This answer is a specific, works for me, solution for an Oracle Forms Application launched via an Internet Explorer link, and running in a java.exe process. In that situation, the 3 Thread Groups are as shown in the question: main, Plugin Thread Group, and http://xxxx.xxxx.xxxxx.xx:8001/OA_JAVA/-threadGroup Your mileage may vary.
  • If you don't use full reflection, but instead do import sun.awt.AppContext, the compiler may emit warnings in the form warning: sun.awt.AppContext is Sun proprietary API and may be removed in a future release That's not very cool, but I will live with that, for the time being.
  • In the run method, I tested OK with the simulatePush method of oracle.ewt.lwAWT.AbstractButton.
  • The method emulated here is invokeLater. For invokeAndWait, more code is needed around the postEvent call. See some sources for the EventQueue class, as a starting point.

To get the correct EDT thread regardless of your thread group, you can use SunToolkit.targetToAppContext(Object target), and for the parameter you can feed it the AWT component you intend to act on. Example source.

Then get the EventQueue using EventQueue eq = SunToolkit.getSystemEventQueueImplPP(appContext);

Finally, create a new InvocationEvent with your runnable and call postEvent on the EQ.

You should be able to extend VButton class Your class definition should be something like:

public class AmazingButton extends VButton implements FocusListener

Then you need an init class like:

public void init(IHandler handler)
  {
    m_handler = handler;
    super.init(handler);
    addMouseListener(new ButtonMouseAdapter());
    addFocusListener(this);
  }

And then afterwards you need to implement the listeners and do some stuff in it:

public void focusGained(FocusEvent e)
     {
         if (e.getComponent() == this)
         {
             // put the focus on the component
             e.getComponent().requestFocus();
             bFocus = true ;
         }
     }

  public void focusLost(FocusEvent e)
     {     
       bFocus = false ;
     }

  /**
   * Private class to handle user mouse actions
   */
  class ButtonMouseAdapter extends MouseAdapter
  {
    /**
     * User moved the mouse over the button
     */
    public void mouseEntered(MouseEvent me)
    {
      bFocus=true ;
      mouseON();
    }

    /**
     * User moved the mouse out of the button
     */
    public void mouseExited(MouseEvent me)
    {
      bFocus=false ;
      mouseOFF();
    }
    /**
     * User moved the mouse out of the button
     */
    public void mousePressed(MouseEvent me)
    {
      bPressed = true ;
    }
    /**
     * User moved the mouse out of the button
     */
    public void mouseReleased(MouseEvent me)
    {
      bPressed = false ;
    }

  }

I hope this code works for you.

Regards

I successfully injected my own Java code in a running Oracle Forms application, using DLL Injection and some jni trickery.

That is the real problem here, IMO.

You are suffering from target fixation, which means that you, the programmer, has a fixed mental idea of what kind of solution they want and this blinds you to everything else. Target fixation has resulted in plane crashes, as even highly experienced and intelligent pilots ( in fact whole cockpits ! ) have become so fixated on one issue in one mindset that they let other disasters slip right by.

Get out of this frame of mind.

Your desired solution is not working out, so move on and try something else. Like the sensible option already presented to you by @nightfox79 and variations on that.

You are trying to circumvent a complex object class, when you should probably simply be extending the existing class you are trying to hack your way around. That's the whole basis of OOPs development.

DLL/JNI Trickery has no place in a sensible solution, IMO.

And I pity the person who has to maintain and repair any code solution based on a DLL/JNI hack. That way madness lies.

Your theory that invokeLater() is not running under the right EDT is probably wrong. invokeLater() will, according to the documentation, always queue the code you request onto the pending code list for the AWT Event handler, which is precisely where it should be. Trying to bypass that is almost certain to cause ghastly problems. The entire purpose of invokeLater() is to defer heavyweight processing in the EDT you invoke it from, and run it later on the exact same thread. It's a bug in invokeLater() if it does not, IMO.

If, however, you wish to check what thread code is running in then the only test I know of is to use this in your code ;

if (SwingUtilities.isEventDispatchThread())
{
    System.err.println("Is running on EDT");
}
else
{
    System.err.println("Is not running on EDT");
}
标签
java
java-native-interface
event-dispatch-thread
oracleforms
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