Is there a way to intercept the system keys in Java so that the events are not propagated to the operating system? Ctrl+Alt+Del or other security related combinations do not matter, the main problem is for example the Windows key.
The program in question is a for a full screen application that performs some remote operations via a proprietary protocol. Currently my only idea would be to solve this via JNI, whereas the solution for Windows seems to be simple, I'm not sure about Linux and MAC OS X.
I'd prefer a somewhat standard solution, maybe there is something for Java games or so.
Java processes the key strokes after the operating system (OS), so Java can't "intercept" them. Although, you could code OS specific stuff in C/C++ that intercepted the keystrokes and call it in Java using JNI.
This appears to be fixed in Java 5, so you could have a shot at it. Apparently, the KeyEvent class in the Java API exposes two Microsoft Windows keyboard specific events - VK_WINDOWS (for the left and right winkeys) and VK_CONTEXT_MENU (for the context menu key).
It is quite possible to trap these events by implementing a KeyListener, but be forewarned that if you attempt to capture the Winkey event alone, you're bound to trip the event handler of the OS first, before Java can process it.
Related
I have this example to listening events from fileSystem (http://java.dzone.com/news/how-watch-file-system-changes) but the events are only create, delete or modify.
I want to listen a simple double click event from my fileSystem.
Does anyone know how to do it? I can't do it by swing.
Thanks!
Java, out of the box, is not capable of watching for "a simple double click event from my fileSystem".
The link you mention is about java code that can watch for other types of events, such as create, delete and modify within the file system, but double clicks are "user interface" events, which are not covered by java code as such.
However, you have rightly mentioned Swing.
If you wrote a programme, using Swing, that was specifically designed to make changes to the file system, then yes, your programme could be written to listen for clicks on a button on a swing layout, and your code could then decide what to do with that click event.
There is no such thing as a "double click event" in terms of the subject you're talking about.
The WatchService in Java is an interface with the implementation being platform specific (including being completely optional, depending on the platform).
The way the default implementation works on some platforms (specifically, windows / *nix) is by periodically polling the filesystem metadata for the directory you specified. If the default implementation is not monitoring access time (atime) or it's not available on the platform (or is turned off), then ... no, you can't get events for file access.
Testing this on OSX, it does not. I would have to test it on Windows and *nix to see what the results were there. I don't know that any of the default implementations do as atime isn't really reliable as it can be turned off on many file systems that support it to improve performance.
If you wanted to use the WatchService interface for this and the platform(s) your code would run on support it, you could implement your own that looked at access time and fired an event.
This StackOverflow Question demonstrates how to check atime on a file, but again remember it's not really reliable (read the comments on the caveats).
I want to capture key event at all time, even when my application is not in focus. For instance, My application should detect Ctrl+SPACE key combination while the focus is with other application, and should respond accordingly. Thanks
This is OS Specific, out of the JVM scope.
Here are two good open source Java libraries for achieving what you want:
JIntellitype - Windows
JXGrabKey - X11
Both are JNI Wrappers.
not possible with pure Java, when applications lost Focus, then Focus Subsystem is managed by Native OS, there exist some way how to do by unsing JNI, notice Key ShoutCuts should be Anti_Virus sensitive
Im making an application that should see if your online or away.
So i need to somehow see when the user hit a key on the keyboard last time.
The application is running in the background and you can only access it from the trey.
Is this possible and if it is how would i check.
Best regards
I believe that what you're looking for can be done via a global keyboard hook, but that doesn't have direct support in the JVM. From Googling, it would appear that your only options are to write a C++ shim which you can use via JNI, or go via libffi with JRuby.
From what I've read here it is not possible to add KeyListener to the SystemTray. The only listener that is supported, is the PropertyChangedListener.
Furthermore from that question it seems to be possible on Windows but not on Linux and MacOS.
This is possible, but not using Java. You'll have to use JNI to access OS APIs that provide this information (and implent it differently for each OS).
I would like to write a program which can monitor activity of my keyboard. In more details, the Java program should "see" which key is pressed/released and when. All this information should be stored in a given file.
First of all I would like to know if it's possible to do it with Java. I know that it's possible if I type in a text field generated by Java program. But is it possible for Java to monitor the keyboard activity if I type, let say, in a text field of a browser or, for example, in word (or open office) document?
These events are directed to the window which has the focus, from all events on the desktop you can only get the mouse position.
import java.awt.MouseInfo;
public class Mouse {
public static void main(String[] args) {
while ( true ) {
System.out.println( MouseInfo.getPointerInfo().getLocation() );
}
}
}
For capturing sysem wide (what you need for word) you need to include a native lib
Code example for windows: Native keyboard mouse hook
Forget JNI and JNA.
There is now a new library for native mouse&keyboard access that works exactly the same as MouseXxxListener and KeyListener. In other words, it's a familiar interface so you don't have to learn anything new (except for how you link an external library).
https://code.google.com/p/jnativehook/
Forget JNI
JNA is the solution (is based on JNI but it's way easier although most people don't use it thinking it's as difficult as JNI, but it's not)
Check https://github.com/twall/jna/
and specifically in the middle of the page where it says: Platform / Platform Documentation
If you download the platform.jar (and check the sourcecode) you'll find a wrapper around
User32.dll where you can find the win32 function
GetAsyncKeyState(int vKey)
mapped to a corresponding java function
(see h**ps://jna.dev.java.net/javadoc/platform/com/sun/jna/platform/win32/User32.html)
There u can check the state of a key (pressed or released)
If you need a global key listener have a look at my other reply to:
h**p://stackoverflow.com/questions/696170/java-keylistener-without-window-being-open/4394398
Thanks to Stackoverflow i can't post more than one working link in my replies :(
Cheers
It's likely possible to write a Java-based key logger using some native libraries, although be aware that such a program is likely more noticeable than one with a different technology, since the Java VM will need to be running for it to work. Keep that in mind if you're trying to be clandestine.
Also, if you just need such a program for use, and don't have to develop it yourself, there are many hardware and software keylogging systems already out there that you could use instead.
I think that native functions can do it.
It's something like you can connect c++ with Java.
http://en.wikipedia.org/wiki/Java_Native_Interface
What you are requesting is not possible using the Java API. In order to do system-wide key logging you need to register with win32 (or other OS native) hooks. Specifically, this will be done using native libraries and interfacing with the JNI.
There are some code snippets over at http://forums.sun.com/thread.jspa?messageID=3808163#3808163. It's a good example of how to get started with JNI and registering a Java callback to a win32 hook.
I'm looking for a way to know in a Java application (without JNI - it's a multi-platform application) can detect if the screen is locked.
For information... our application records time while a user is working - we want it to automatically stop recording when the screen is locked instead of the user having to do so explicitly.
I don't think there is an API for that or even a way to do it all. Parsing screenshots generated by java.awt.Robot is neither platform- nor version- or even configuration-independant, and in general, I don't think "screen is locked" is a well-enough defined concept to be used in this sense - on Linux, there can be more than just one "screen" (X server), you can switch to console terminals, you can have applications running one (or more) machines display their GUIs on another machine over the network...
I confirm there seems to be no Java API to detect a screen lock status.
Spark developer gave it a try in 2006 (like this thread shows), but without giving out any details on the specific of the implementation.
However, it is likely it involved JNI and native call to functions like WTSQuerySessionInformation (To detect if disconnected use WTSQuerySessionInformation(NULL, WTS_CURRENT_SESSION, WTSConnectState) and look for WTSDisconnected).
So, as Michael pointed out, there is no "multi-platform" universal answer (to the best of my knowledge).