Abort Windows log off from Java - java

I have an Swing application in which the user can create and save documents. The application is deployed as a simple Jar-file.
The primary target platform is Windows Vista.
If the user has on opened and non-saved document in the application and the user is logging out from the Windows Vista machine I would like to halt the logging off process and ask the user if he wants to save to document before the Java application is terminated.
Is it possible to halt the logging off process on Windows Vista from an Java application?
I've tried the shutdown hook with no success.

Is it possible to halt the logging off process on Windows Vista from an Java application?
No, nor should it be possible. That's like the tail wagging the dog.

EDIT2
For those who followed the discussion I leave the first answers I had but it seems like they don't work. First find my real solution.
Ok, so I think this actually works but it is not totally acceptable as it used restricted part of the API (but it exists since Java 1.3 and is still present in Java 1.7). It uses sun.misc.Signal. Most of the code has been originally posted by Andrew Thompson.
import java.awt.AWTEvent;
import java.awt.EventQueue;
import java.awt.Toolkit;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import javax.swing.JFrame;
import javax.swing.JOptionPane;
import javax.swing.SwingUtilities;
import sun.misc.Signal;
import sun.misc.SignalHandler;
class TestShutDown {
static final String WINDOW_MODIFIED = "windowModified";
TestShutDown() {
final JFrame f = new JFrame("Log Off!");
f.setDefaultCloseOperation(JFrame.DO_NOTHING_ON_CLOSE);
f.addWindowListener(new WindowAdapter() {
#Override
public void windowClosing(WindowEvent we) {
System.err.println("Window closing");
handleQuit(f);
}
});
Signal.handle(new Signal("TERM"), new SignalHandler() {
#Override
public void handle(Signal arg0) {
handleQuit(f);
}
});
// bad practice, but not the point..
f.setSize(400, 200);
f.setLocationByPlatform(true);
f.setVisible(true);
}
protected static void handleQuit(final JFrame f) {
int result = JOptionPane.showConfirmDialog(f, "Close Me");
if (result == JOptionPane.OK_OPTION) {
System.exit(0);
}
}
public static void main(String[] args) {
// start the GUI on the EDT
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
new TestShutDown();
}
});
}
}
SOLUTION EARLIER SUGGESTED (NOT WORKING ON LOGOFF)
I am assuming that you are using a GUI application with a JFrame.
In your JFrame, set the following:
setDefaultCloseOperation(WindowConstants.DO_NOTHING_ON_CLOSE);
Then, register a WindowAdapteron your JFrame. Override the windowClosing() method and from there open a blocking dialog to ask the user what he wants to do (Yes/NO/CANCEL). In case he chooses, YES, you save and then dispose the frame, in case he chooses NO, you just dispose the frame. If he chooses cancel, you don't do anything.
EDIT:
Here is some code and more details on what I was explaining and that have been brought by Andrew Thompson. All credits should go to him for the following:
Using this code:
import java.awt.event.*;
import javax.swing.*;
class TestShutDown {
TestShutDown() {
final JFrame f = new JFrame("Log Off!");
f.setDefaultCloseOperation(JFrame.DO_NOTHING_ON_CLOSE);
f.addWindowListener( new WindowAdapter() {
#Override
public void windowClosing(WindowEvent we) {
int result = JOptionPane.showConfirmDialog(f, "Close Me");
if (result==JOptionPane.OK_OPTION) {
System.exit(0);
}
}
});
// bad practice, but not the point..
f.setSize(400,200);
f.setLocationByPlatform(true);
f.setVisible(true);
}
public static void main(String[] args) {
// start the GUI on the EDT
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
new TestShutDown();
}
});
}
}
Then telling Windows to shut down, I see..
Even more interestingly, after I hit Cancel ( heck, 'Searching for UFOs' was the next queued track in the player, and I was not about to reschedule it :), I could not click on the frame. It seemed as though it was blocked with an invisible modal dialog. I had to kill the VM to be rid of it.

Related

What kind of voodoo is necessary to get the glassPane visible and valid for an JInternalFrame?

I have a project where I use JDesktopPane for the main application and a bunch of JInternalFrames for a series of independent analyses.
Certain bits of the analyses are time-consuming thus I run them on SwingWorkers, but I would like to both disable the GUI (so no actions are queued) and inform the user that some action is going on and that it's normal.
Previously I have used a custom GlassPane for that purpose, and it has worked nicely before. Now I am experiencing some issues, using the same class as before. Specifically, the glassPane intercepts user input, expected but no visual cue is visible, which makes me think that the paintComponent() is never called on the glassPane.
Just to be sure I googled and came across another implementation (called DisabledGlassPane) of the "please-wait-glassPane" concept but to no success really. While trying to debug the issue I realised that when I start/activate my glassPane it is invalid by default and does not get validated by itself.
If I specifically call validate() on the JInternalFrame after activating the glassPane, it appears to be valid and visible, based on the properties of the glassPane but I see nothing on the screen (both GlassPane implementations have color and text based features that should be immediately visible to the user).
EDIT:
Below is the relevant piece of the code, extracted out of the bigger scheme of things into a minimalist, self-contained (with the exception of the DisabledGlassPane class mentioned above, omitted for the sake of brevity) example. When I run the DesktopFrame class below, and click the button the calculations start, the cursor changes to waiting mode, however the screen is not grayed out, and the message to the user is not displayed, hence my suspicion of paintComponent is never actually called..
I am primarily wondering if I have made an obvious miss, since I am not that experienced with GUI programming and Swing.
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.concurrent.ExecutionException;
import javax.swing.JButton;
import javax.swing.JDesktopPane;
import javax.swing.JFrame;
import javax.swing.JInternalFrame;
import javax.swing.SwingWorker;
import javax.swing.event.InternalFrameEvent;
import javax.swing.event.InternalFrameListener;
public class DesktopFrame extends JFrame implements InternalFrameListener{
private JDesktopPane dpane;
private JInternalFrame f;
static DisabledGlassPane gp = new DisabledGlassPane();
public DesktopFrame() {
dpane = new javax.swing.JDesktopPane();
dpane.setPreferredSize(new java.awt.Dimension(1020, 778));
setContentPane(dpane);
addFrame();
pack();
}
public JInternalFrame addFrame(){
f = new JInternalFrame("test");
f.setGlassPane(gp);
f.addInternalFrameListener(this);
f.setLayout(new GridLayout());
f.setPreferredSize(new java.awt.Dimension(400,300));
f.add(new javax.swing.JLabel("something something"));
f.add(new javax.swing.JTextArea(10, 10));
javax.swing.JButton but = new JButton("click me!");
but.setPreferredSize(new java.awt.Dimension(100,50));
but.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
gp.activate("Please wait...");
SwingWorker<Void, Void> worker = new SwingWorker<Void, Void>() {
#Override
protected Void doInBackground() throws Exception {
for(float i=-3000; i < 3000; i = i + 0.01f){
double exp = Math.pow(2,i);
double fac = Math.pow(i, 2);
System.out.println(exp/fac);
}
return null;
}
};
worker.execute();
try {
if(worker.get() == null)
gp.deactivate();
} catch (InterruptedException | ExecutionException e1) {
e1.printStackTrace();
}
}
});
f.add(but);
f.setVisible(true);
f.pack();
dpane.add(f);
try {
f.setSelected(true);
} catch (java.beans.PropertyVetoException e) {
e.printStackTrace();
}
dpane.repaint();
return f;
}
public static void main(String args[]) {
/* Create and display the form */
java.awt.EventQueue.invokeLater(new Runnable() {
public void run() {
DesktopFrame df = new DesktopFrame();
df.setLocationRelativeTo(null);
df.setVisible(true);
df.setDefaultCloseOperation(EXIT_ON_CLOSE);
}
});
}
#Override
public void internalFrameOpened(InternalFrameEvent e) {}
#Override
public void internalFrameClosing(InternalFrameEvent e) {}
#Override
public void internalFrameClosed(InternalFrameEvent e) {}
#Override
public void internalFrameIconified(InternalFrameEvent e) {}
#Override
public void internalFrameDeiconified(InternalFrameEvent e) {}
#Override
public void internalFrameActivated(InternalFrameEvent e) {}
#Override
public void internalFrameDeactivated(InternalFrameEvent e) {}
}
but I would like to both disable the GUI (so no actions are queued) and inform the user that some action is going on and that it's normal.
Check out the Disable Glass Pane for a general solution you might be able to use. The above class intercepts mouse and key events and allows you to display a message while the glass pane is visible.

SwingWorker setting a flag after finishing its work

I have put together an application that opens text files and allows users to edit them (eg: text editor)
Some text files can be arbitrarily large, so it would take some time to open them. I have added a progress bar to inform the user that stuff is actually happening, and am using a swing worker to perform the actual file loading, giving it a reference to a text area to dump all the text.
I also have a flag in the main application called isFileLoaded which is true if there's a file open, and false otherwise. Ideally, the swing worker should set that value after it finishes loading the file and doing any processing that it needs to do.
I have written the swing worker as a separate class, so it's not nested inside my main Frame class that holds all of the GUI logic, mainly because I do not like to define classes inside classes purely for aesthetic reasons. As such, I am currently passing a reference to the entire Frame to the swing worker and letting it set the value of the flag.
Is this a good way to do things? Are there better ways?
Consider rather adding a PropertyChangeListener which holds a reference to your Frame (an anonymous inner-class would be just fine for that matter) and which listens to the "state" property. The value of the event will be equal to StateValue.DONE when the SwingWorker has finished.
Here is a fully working example:
import java.awt.BorderLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.beans.PropertyChangeEvent;
import java.beans.PropertyChangeListener;
import java.util.List;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JProgressBar;
import javax.swing.SwingUtilities;
import javax.swing.SwingWorker;
import javax.swing.SwingWorker.StateValue;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
public class TestSwingWorker {
private JProgressBar progressBar;
protected void initUI() {
final JFrame frame = new JFrame();
frame.setTitle(TestSwingWorker.class.getSimpleName());
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JButton button = new JButton("Clik me to start work");
button.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
doWork();
}
});
progressBar = new JProgressBar(0, 100);
frame.add(progressBar, BorderLayout.NORTH);
frame.add(button, BorderLayout.SOUTH);
frame.pack();
frame.setVisible(true);
}
private boolean someFlag;
protected void doWork() {
SwingWorker<Void, Integer> worker = new SwingWorker<Void, Integer>() {
#Override
protected Void doInBackground() throws Exception {
for (int i = 0; i < 100; i++) {
// Simulates work
Thread.sleep(10);
publish(i);
}
return null;
}
#Override
protected void process(List<Integer> chunks) {
progressBar.setValue(chunks.get(chunks.size() - 1));
}
#Override
protected void done() {
progressBar.setValue(100);
progressBar.setStringPainted(true);
progressBar.setString("Done");
}
};
worker.getPropertyChangeSupport().addPropertyChangeListener("state", new PropertyChangeListener() {
#Override
public void propertyChange(PropertyChangeEvent evt) {
if (StateValue.DONE.equals(evt.getNewValue())) {
someFlag = true;
}
}
});
worker.execute();
}
public static void main(String[] args) throws ClassNotFoundException, InstantiationException, IllegalAccessException,
UnsupportedLookAndFeelException {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
new TestSwingWorker().initUI();
}
});
}
}
You should restructure your code a little to avoid using the whole Frame which indeed is not really clean (but if it works who cares).
If you want to be more cool from a design point of view you should use a model:
class FileModel
{
boolean isLoading;
// getter and setter that notifies
}
and pass only this model to your worker, and once done set the flag.

Java Applet Game Design : Keyboard focus

I had posted this in a wrong place (GameDev) and got no response there. So I'm posting it again here.
I'm making an applet game and it is rendering, the game loop is running, the animations are updating, but the keyboard input is not working. Here's an SSCCE.
public class Game extends JApplet implements Runnable {
public void init(){
// Initialize the game when called by browser
setFocusable(true);
requestFocus();
requestFocusInWindow(); // Always returning false
GInput.install(this); // Install the input manager for this class
new Thread(this).start();
}
public void run(){
startGameLoop();
}
}
And Here's the GInput class.
public class GInput implements KeyListener {
public static void install(Component c){
new GInput(c);
}
public GInput(Component c){
c.addKeyListener(this);
}
public void keyPressed(KeyEvent e){
System.out.println("A key has been pressed");
}
......
}
This is my GInput class. When run as an applet, it doesn't work and when I add the Game class to a frame, it works properly.
Thanks
Solved now. See my solution
One possible solution is to use the JApplet's contentPane, to set the focus on it rather than on the JApplet itself. But my preference is to use Key Bindings instead. You may need to use a Swing Timer for this to work:
My SSCCE:
import java.awt.Container;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.lang.reflect.InvocationTargetException;
import javax.swing.*;
#SuppressWarnings("serial")
public class AppletKeyListen extends JApplet {
#Override
public void init() {
try {
SwingUtilities.invokeAndWait(new Runnable() {
public void run() {
setFocusable(true);
int timerDelay = 100;
Timer myTimer = new Timer(timerDelay , new ActionListener() {
#Override
public void actionPerformed(ActionEvent arg0) {
boolean focusObtained = requestFocusInWindow();
System.out.println("focusObtained for JApplet: " + focusObtained);
Container contentPane = getContentPane();
contentPane.setFocusable(true);
focusObtained = contentPane.requestFocusInWindow();
System.out.println("focusObtained for contentPane: " + focusObtained);
}
});
myTimer.setRepeats(false);
myTimer.start();
// boolean focusObtained = requestFocusInWindow();
// System.out.println("focusObtained: " + focusObtained);
//
// Container contentPane = getContentPane();
// contentPane.setFocusable(true);
//
// focusObtained = contentPane.requestFocusInWindow();
// System.out.println("focusObtained: " + focusObtained);
}
});
} catch (InvocationTargetException | InterruptedException e) {
e.printStackTrace();
}
}
}
If you're running in a browser, you probably need to click on the applet to give it focus. For security reasons most browsers won't let an applet just grab the keyboard focus without the user clicking it.
So, I would add a mouse listener instead of doing the focus grabbing directly in init():
addMouseListener(new MouseAdapter() {
public void onMousePress(MouseEvent e) {
requestFocus();
}
});
Now that I have two options,
Use JWS
Don't make an applet mode
Now I had tried to make a new class called GApplet. It loads a game into a new JFrame which worked from the applet. Now I can access the fullscreen mode from web too. Here's a link to the class.
The GApplet class
And now it's working like the webstart and is actually an applet.

Is there an alternative to JPasswordField?

When typing a passphrase like
yeast bulk seize is shows pain
everybody can hear tapping the space bar, so it seems logical to display the spaces in the password field, too. So I'd like something capable of showing
***** **** ***** ** ***** ****
instead of
******************************
This would make typing easier while hardly decreasing the security.
UPDATE
Think twice before you update Riduidel's comment. When Bruce Schneier writes "It's time to show most passwords in clear text", then showing a small part of it must be correct, too. Especially showing a part which may get captured simply by listening.
Here's a variation that uses setEchoChar() to make the password visible for a predefined time: three seconds for example.
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JFrame;
import javax.swing.JPasswordField;
import javax.swing.Timer;
import javax.swing.event.DocumentEvent;
import javax.swing.event.DocumentListener;
/** #see http://stackoverflow.com/questions/5339702 */
public class PasswordTest {
public static void main(String[] args) {
javax.swing.SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGui();
}
});
}
private static void createAndShowGui() {
JFrame jf = new JFrame("Test Password");
JPasswordField jpwd = new JPasswordField();
TimedPasswordListener tpl = new TimedPasswordListener(jpwd);
jpwd.getDocument().addDocumentListener(tpl);
jf.add(jpwd);
jf.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
jf.setLocationRelativeTo(null);
jf.pack();
jf.setVisible(true);
}
}
class TimedPasswordListener implements DocumentListener, ActionListener {
private Timer timer = new Timer(3000, this);
private char echoChar;
private JPasswordField pwf;
public TimedPasswordListener(JPasswordField jp) {
pwf = jp;
timer.setRepeats(false);
}
public void insertUpdate(DocumentEvent e) {
showText(e);
}
public void removeUpdate(DocumentEvent e) {
showText(e);
}
public void changedUpdate(DocumentEvent e) {}
public void showText(DocumentEvent e) {
if (0 != pwf.getEchoChar()) {
echoChar = pwf.getEchoChar();
}
pwf.setEchoChar((char) 0);
timer.restart();
}
public void actionPerformed(ActionEvent e) {
pwf.setEchoChar(echoChar);
}
}
Was thinking JPasswordField was simply a JTextField simply overriding the renderer component, but it seems not to be the case.
So, instead of changing the renderer (like it would be the case if JTextField had such a component), you'll have to use a JTextField with a custom Document holding two strings :
Password text as written by user
Displayed password
You'll have to make sure all Document modifying methods change the password text, while all rendering methods use the displayed one.

Java on a Mac: How do I detect when my application receives focus?

I looked through ApplicationListener, and they don't have it in there. On a Mac, it's when that application has the equivalent of focus; its menu is in the top menu bar.
Also, if you know this, could you tell me how my application can request to de-focus itself?
Implementations of windowActivated() and windowDeactivated() in WindowListener or WindowAdapter will tell you when a window is activated or deactivated. You don't need ApplicationListener for that.
Addendum: Although not required in this case, a transparent implementation of the additional functionality specified in ApplicationListener may be found in this example.
Addendum: See also How to Write Window Listeners.
Addendum: I think I see what you mean. In the example OSXAdapter, which uses -Dapple.laf.useScreenMenuBar=true, the menus disappear when the last window (HIDE_ON_CLOSE by default) closes. It's less than optimal, but the About… and Preferences menus remain in the application menu; choosing either restores the screen menu. Another possibility is to modify the dock menu in com.apple.eawt.Application.
import java.awt.EventQueue;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.WindowEvent;
import java.awt.event.WindowFocusListener;
import java.awt.event.WindowListener;
import java.awt.event.WindowStateListener;
import javax.swing.JButton;
import javax.swing.JFrame;
public class WindowTest extends JFrame implements ActionListener,
WindowListener, WindowFocusListener, WindowStateListener {
public static final void main(String args[]) throws Exception {
EventQueue.invokeLater(new Runnable() {
#Override
public void run() {
new WindowTest("One");
new WindowTest("Two");
}
});
}
public WindowTest(String name) {
super(name);
this.setName(name);
this.setLayout(new GridLayout(0, 1));
createButton("Back");
createButton("Front");
createButton("Hide");
this.addWindowListener(this);
this.addWindowFocusListener(this);
this.addWindowStateListener(this);
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
this.setLocationRelativeTo(null);
this.pack();
this.setVisible(true);
}
private void createButton(String name) {
JButton b = new JButton(name);
this.add(b);
b.addActionListener(this);
}
#Override
public void actionPerformed(ActionEvent e) {
String s = e.getActionCommand();
if ("Back".equals(s)) {
this.toBack();
} else if ("Front".equals(s)) {
this.toFront();
} else {
this.setExtendedState(JFrame.ICONIFIED);
}
}
#Override
public void windowOpened(WindowEvent e) {
System.out.println(e);
}
#Override
public void windowClosing(WindowEvent e) {
System.out.println(e);
}
#Override
public void windowClosed(WindowEvent e) {
System.out.println(e);
}
#Override
public void windowIconified(WindowEvent e) {
System.out.println(e);
}
#Override
public void windowDeiconified(WindowEvent e) {
System.out.println(e);
}
#Override
public void windowActivated(WindowEvent e) {
System.out.println(e);
}
#Override
public void windowDeactivated(WindowEvent e) {
System.out.println(e);
}
#Override
public void windowGainedFocus(WindowEvent e) {
System.out.println(e);
}
#Override
public void windowLostFocus(WindowEvent e) {
System.out.println(e);
}
#Override
public void windowStateChanged(WindowEvent e) {
System.out.println(e);
}
}
could you tell me how my application
can request to de-focus itself?
You can try:
frame.toBack();
If that doesn't work then you can iconify your application in which case focus should go to the previous application.
frame.setExtendedState(...);
The Java programming language is platform-independent. Rather than reading Apple's reference documentation, you should be using the official Java API Reference Documentation. There you will find documentation for JFrame, WindowListener, and WindowAdapter. You can register a WindowListener on a JFrame, using the addWindowListener function. The window listener may be used to intercept and handle a variety of window-related events including activated/deactived (which window is on top) or gained focus/ lost focus (which window will receive keyboard events). If you are supplying your own WindowListener and don't want to implement every single function, WindowAdapter is useful for that purpose as it implements WindowListener but provides empty definitions for each function. As for defocusing (in the sense that you mean), toBack may be used for that, while toFront does the opposite.
Edit
Most of this information was already given in previous posts; however, I added this to emphasize:
Java is a platform-independent language.
Java is a product of Sun Microsystems (now Oracle).
Consquently, using the official Java API Reference Documentation from Sun makes way more sense than relying on any reference documentation provided by Apple, because anything contained within the official API reference documentation will work on all platforms; whereas, anything from Apple's reference documentation may very well to be specific to Apple's implementation.
The reference documentation for JFrame from the official, authoritative reference documentation gives all the information necessary for answering the question (hence yet another reason to consult the official API reference documentation, rather than relying on Apple's documentation).

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