Hi Alex,
if you read the next sentence as well, it should become clear:
> Writing data is only allowed from the UI thread,
> and write operations always need to be wrapped in
> a write action with ApplicationManager.getApplication().runWriteAction().
>
> To pass control from a background thread to the event dispatch thread,
> instead of the standard SwingUtilities.invokeLater(),
> plugins should use ApplicationManager.getApplication().invokeLater().
So your second interpretation is right.
If in doubt, consult the JavaDoc [1] (there is no other site apparently).
For "runReadAction" it says:
> Runs the specified read action. Can be called from any thread.
> The action is executed immediately if no write action is currently
> running, or blocked until the currently running write action completes.
There you see the reason why you need to tell Intellij whether your Runnable is
reading or writing.
For "runWriteAction" it says:
> Runs the specified write action. Must be called from the
> Swing dispatch thread. The action is executed immediately if no
> read actions are currently running, or blocked until all read
> actions complete.
If you go on reading you might notice "isDispatchThread" which you could
call first to determine whether you even need to call "invokeLater".
Or you could've asked Google (that's what I did).
In the Intellij support forum [2] you'll find the following idiom:
Application application = ApplicationManager.getApplication();
if (application.isDispatchThread()) {
application.runWriteAction(runnable);
} else {
application.invokeLater(()-> application.runWriteAction(runnable));
}
The last statement contains a Lambda expression, which Java 7 does not support,
so it would expand to:
application.invokeLater(new Runnable() {
@Override
public void run() {
application.runWriteAction(runnable);
}
});
Franz
[1]
https://github.com/JetBrains/intellij-community/blob/master/platform/core-api/src/com/intellij/openapi/application/Application.java
[2]
https://intellij-support.jetbrains.com/hc/en-us/community/posts/206754235-Write-access-is-allowed-inside-write-action-only-see-com-intellij-openapi-application-Application-runWriteAction-
-----Original Message-----
From: Alexander Jakobi [mailto:[email protected]]
Sent: Thursday, September 22, 2016 3:10 PM
To: [email protected]
Subject: [DPP-Devel] IntelliJ Thread Rules
Hey guys,
I'm wondering about a thing in this [1] part of the IntelliJ Platform
SDK DevGuide:
"Writing data is only allowed from the UI thread, and write operations
always need to be wrapped in a write action with
ApplicationManager.getApplication().runWriteAction()."
Does this mean only the UI thread is allowed to write without wrapping
the commands in a call
ofApplicationManager.getApplication().runWriteAction()?
And does this mean when writing from another thread, you will need to
wrap ApplicationManager.getApplication().runWriteAction() around your
commands?
OR
Does this mean you have to wrap
ApplicationManager.getApplication().runWriteAction() around the code you
want to execute, and wrap another move to the UI thread
(ApplicationManager.getApplication().invokeLater()) around it. Thus
writing from a non-UI thread is never ever allowed?
Does anybody know?
Thanks,
Alex
[1]
http://www.jetbrains.org/intellij/sdk/docs/basics/architectural_overview/general_threading_rules.html
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