How can I disable OS-level keyboard shortcuts (e.g. Alt-Tab, Ctrl-Alt-Left/Right, etc.) on a [Ubuntu] Linux machine? I'm developing a full-screen Java Swing app and don't want the user to be able to task switch away from the program arbitrarily. It's not enough to toggle the "always on top" flag; users mustn't be allowed to switch workspaces, migrate focus or any other such things. The machine must function normally before and after the application is executed. Google says that this will require JNI or JNA but I'm looking for a bit more hand-holding.
There's no point in trying to do this in your application because any of these changes are going to need to be handled by X11 and/or the window manager since those are what respond to the commands. Assuming that you have control of the platform, choose a window manager which supports a kiosk mode. Then use the window manager's settings to start your application and enter kiosk mode.
Options for window managers which can do this include KDE or twm-kiosk.
(And if you don't have control of the platform, you're not likely to be able to have your application intercept things like ctrl-alt-backspace anyway.)
Edit:
In response to a scaled-down version of the question in which he's willing to let things like ctl-alt-backspace go and just wants most of the keys including alt-tab or other similar application switching key combinations, the following should work:
You should be able to do this using XLib's XGrabKeyboard method through JNI. This Java/XLib JNI keypress capture tutorial should be a good starting point. However, it uses XGrabKey which just passively listens for keys and does not prevent other applications from receiving them. You'll instead want to use XGrabKeyboard which actively snags all of the normal keyboard events (which, if the premise of this StackOverflow question is correct, includes the task switching keys).
Note that as a side-effect, key capture in Swing will also probably stop working because your Swing windows are going to be separate from the window you create in C. As such, you will probably have to use your JNI interface to get key presses to your program when needed. (Although I would definitely advise testing it first before writing the code.) You might be able to avoid this if you can get the window using Java AWT Native Interface to get the window ID. (Note that Swing is built on top of AWT, so this will work for Swing.) However, I'm not sure how to do this. It looks like you might be able to navigate the window tree by getting the root window from the Display and going from there to find your Window, but it's all kind of weird. It would be nice if the AWT NI just told you the window ID, but it doesn't look like it does that.
As this warning Reminder: XGrabKeyboard is not a security interface notes, this doesn't make it impossible for other programs to see the keys, but it seems likely that window managers will not be using XQueryKeyMap so it is likely to prevent task switching.
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I code in java. I wrote a keylistener for the frame and it prints all the keystrokes when the frame is active, but when i minimize it or deactivate it, the program obviously stops and no keystrokes are printed. I wanted to make a small game where i enter a key and using the robot class, it presses another set of keys but this game is in flash. any idea as to how i would capture keystrokes when window is deactivated.
edit: I only code in java so is it possible using only java or at most combining it with native machine... i use windows
By its nature, Java is sandboxed by the JVM, so you will have to incorporate some kind of native methods. There already exists a very flexible and helpful library to accomplish this under open source, called JNativeHook. It's very easy to hook in, especially if you're already familiar with Swing event handlers. Same basic concept, except it leverages native code written in C. It supports all of the basic operating systems (Windows, Mac, *Nix).
I'm trying to create a Window class which I can use to open multiple windows, and which will automatically add an event handler to listen for the Swt.CLOSE event, and call the shell.dispose() method when it is called.
My questions are:
Do I need to listen for shell.dispose() in this case, or to only listen for display.dispose() in my main method?
Do I need to run each window in its own thread, or can all the windows share the same UI thread? I've read some reports of buggy behavior related to event handling in case of multiple windows being open.
I recommend you should always have a single UI thread, which the single Display object runs on. See SWT: single vs. multiple displays or even the Eclipse documentation on Display that strongly recommends using a single Display object:
Applications which are built with SWT will almost always require only a single display. In particular, some platforms which SWT supports will not allow more than one active display.
There are even several sample apps available (such as this one) that demonstrate multiple shells in SWT. Calling shell.dispose() when you want to close a window is the way to go.
You should only use display.dispose() when you are shutting down the entire app, basically as a 'last step' - see this example, or this one, or pretty much any snippet on the SWT Snippets page.
Edit
The Eclipse framework itself is an example of an application that can have multiple windows - it still uses a single Display, with a single UI Thread and shared event system. Eclipse documentation on Threading Issues has a basic explanation of this:
Underneath any GUI application, regardless of its language or UI toolkit, the OS platform detects GUI events and places them in application event queues. [...] It determines which window and application should receive each event and places it in the application's event queue.
I would like to have an application running in a linux box with a touchscreen monitor.
I don't want to use Flash player (with full window size), so my question is, what I should use instead of a Flash Player?
This box is gonna be in a place with a lot of kids, so they can close the application and shutdown the machine XD.
I'm not a Sr. Java developer, so I don't know if theres something over there to block the 'close window' feature in an java application.
Thanks in advance!
Assuming you're using swing, you could use Frame.setUndecorated(true) and maximize it. There is also the option of exclusive full screen mode. From there, you'll have to unbind any global keys that map to window-exiters/taskmanagers/other-utils.
You may also want a watcher/spawner script setup to make sure your app stays up. I bet there is a more elegant way to do this but most window managers try to avoid an app doing this due to malicious possibilities.
I need to write a program that, when minimized, lives in the System Tray, and I'll use Java 6's SystemTray API to do that.
How can I make that application comes to the foreground when the user presses some hotkey?
For example, the app is running but minimized. When the user presses CTRL-SHIFT-Y or something (or, like Google Desktop's search, CTRL twice) and the application is maximized.
EDIT: I know about how to bring a Java window to the foreground. I'm asking more specifically about how to make a running Java app listen for a hotkey.
You're going to need to resort to JNI, check out an example.
Here's another nice example from Sun's forums.
You can use the following SWT extension library to create a keyboard hook that can listen for your hot key - http://feeling.sourceforge.net/
note, that this is windows only (but that may not be a problem for you).
I am creating an application that is essentially a financial alerts site. I am a basic level Java programmer, and I have created some of the logic for alerts in Java.
I want to be able to have pop-ups appear on the desktop whenever something "interesting" happens (interesting depends on %change, liquidity and a few other simple factors).
What is the best combo of technology to implement something like this?
I would use the java.awt.SystemTray in Java SE 6. It's cross-platform and pretty easy to use.
Although some people hate the balloon notifications in Windows, they're the least obtrusive popups, since they can be ignored by the user or easily dismissed. Most importantly, they can't be missed by the user who has been away from the computer, because balloons (at least in Windows XP/Vista) use system idle timers to determine when's the right time to disappear.
Some prefer more traditional toast notifications, similar to those shown by Outlook - they show up and slowly fade out, giving the user some time to interact with them if needed.
I had the same problem and finally solved it using an undecorated, alwaysOnTop window.
And thanks to this blog entry I found the TimingFramework, and now it even is translucent, fades in and out, goes 100% opaque on mouse over etc. In conjunction with the SystemTray and TrayIcon the behavior is nearly as that of Outlook.
Oh, I have to note, that other than the second link, I do the fading out with
AWTUtilities.setWindowOpacity(window, op);
You could write a java program that resides in the system tray, but I am not sure if there are cross platform compatible ways to do this. maybe you have to use a platform specific library for Win, Mac, Linux, ...
I'd just create a message window and animate it. Then add SystemTray support and voila, you're done.
In Delphi you can do that pretty quickly, but you can't easily reuse your java logic
You can just run you program in "silent" mode, without creating any windows by default, maybe just a little icon in the taskbar which when double-clicked will open a settings window. The program will be running in the background and creating windows with the set focus whenever an event happens.
But in my opinion, a slide window or at least a balloon tooltip is a better idea.