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What needs to/doesn't need to be run on the EDT?  RSS feed

 
Louis Denning
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Due to the way AWT/Swing works, code that updates GUI elements should be run on the EDT. However, I'm not sure what doesn't need to be run on the EDT. For example, amongst other things, when initializing a window (like a JFrame, for instance), or setting its dimensions/location before it is first displayed/made visible, need it be run on the EDT? Should I just wrap everything in a SwingUtilities.invokeLater call?
 
Campbell Ritchie
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Yes, it does need to be run on the EDT. The only thing snot to run on the EDT shou‍ld be long‑running tasks which are completely independent of the display. The threads for such tasks are often called worker threads. Have a look in the Java™ Tutorials.
By the way: calling invokeLater simply starts the EDT, so that bit sounds correct.
 
Stephan van Hulst
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Campbell Ritchie wrote:By the way: calling invokeLater simply starts the EDT, so that bit sounds correct.

To be pedantic, it's usually Component.setVisible() or Window.pack() that start the EDT. invokeLater() just adds tasks to the event queue.
 
Norm Radder
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Interesting point.  What thread does the task started by invokeLater() execute on if the EDT hasn't been started by a method like: Component.setVisible() or Window.pack()?
 
Stephan van Hulst
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Just speculating here, but I imagine nothing happens, and the task just remains in the queue until the EDT is started.
 
Norm Radder
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When in doubt, write a test program:
This was in my non-GUI main for testing.  The output:

Running: java.exe -client -cp . TestCode22

This might well be displayed before the other message.
>>> main exiting <<<
Hello World on Thread[AWT-EventQueue-0,6,main]

0 error(s)
 
Stephan van Hulst
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Whelp, so much for speculation.
 
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