Groups > comp.lang.java.programmer > #39417

Re: How can I read individual keystrokes?

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From	Arne Vajhøj <arne@vajhoej.dk>
Newsgroups	comp.lang.java.programmer
Subject	Re: How can I read individual keystrokes?
Date	Sat, 4 Apr 2020 22:04:13 -0400
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On 4/4/2020 8:17 PM, Martin Gregorie wrote:
> I have a need to read individual key presses as they are made. I'm
> developing this stuff under Linux with OpenJava 1.8 and would prefer a
> portable Java solution if that's possible.
> 
> I have a working solution, but its ugly. A small C program captures the
> one or more characters emitted as a key is pressed and sends them
> individually to my Java application over a local network session.
> 
> I've also tried using the Reader.read() method of the Reader instance
> returned by calling Console.reader() but that uses line buffering
> internally. As a result the Java code doesn't get sent anything until I
> hit RETURN, when all the characters typed since the last RETURN are sent,
> followed by the LF, so is of no use here.
> 
> Also, there's a good chance that the C program is using OS-specific
> features to let it capture individual keystrokes.
> 
> I have a feeling that I'm missing something obvious and so would
> appreciate it if any of you can point me in the direction of a pure Java
> way to capture individual key presses.

For a Swing app then it is easy: KeyListener.

For a console app it is a problem.

Some of the common workarounds are:
* use JNI and some OS specific C code
* use an existing library that does the above (like jCurses)
* use an OS specific command (stty on Linux) to put console
   in single character mode and use System.in.read()

Arne

Thread

How can I read individual keystrokes? Martin Gregorie <martin@mydomain.invalid> - 2020-04-05 00:17 +0000
  Re: How can I read individual keystrokes? Eric Sosman <esosman@comcast-dot-net.invalid> - 2020-04-04 20:38 -0400
  Re: How can I read individual keystrokes? Arne Vajhøj <arne@vajhoej.dk> - 2020-04-04 22:04 -0400
    Re: How can I read individual keystrokes? Martin Gregorie <martin@mydomain.invalid> - 2020-04-05 11:22 +0000

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