Develop Reference

NPE when calling new JPanel() in headless (RepaintManager.currentManager)

I'm running a headless linux box with openjdk-8-jdk-armhf and when I run my application, the line
METRICS = new JPanel().getFontMetrics(FONT);
Throws a NullPointerException reaching back to RepaintManager.currentManager(RepaintManager.java:262), which looks like this:
public static RepaintManager currentManager(Component c) {
// Note: DisplayChangedRunnable passes in null as the component, so if
// component is ever used to determine the current
// RepaintManager, DisplayChangedRunnable will need to be modified
// accordingly.
return currentManager(AppContext.getAppContext());
}
The full trace is as follows:
java.lang.NullPointerException
at javax.swing.RepaintManager.currentManager(RepaintManager.java:262)
at javax.swing.JComponent.repaint(JComponent.java:4799)
at java.awt.Component.repaint(Component.java:3303)
at javax.swing.JComponent.setFont(JComponent.java:2756)
at javax.swing.LookAndFeel.installColorsAndFont(LookAndFeel.java:208)
at javax.swing.plaf.basic.BasicPanelUI.installDefaults(BasicPanelUI.java:66)
at javax.swing.plaf.basic.BasicPanelUI.installUI(BasicPanelUI.java:56)
at javax.swing.JComponent.setUI(JComponent.java:664)
at javax.swing.JPanel.setUI(JPanel.java:153)
at javax.swing.JPanel.updateUI(JPanel.java:126)
at javax.swing.JPanel.<init>(JPanel.java:86)
at javax.swing.JPanel.<init>(JPanel.java:109)
at javax.swing.JPanel.<init>(JPanel.java:117)
at lukemoll.MyClass.<init>(MyClass.java:15)
I can reproduce this error both through the jsvc and java commands.

Thanks to Gyro Gearless pointing out this answer.
This (Canvas) will also work in headless mode.
I ended up using new Canvas().getFontMetrics(font);, I'm not sure how I got it to work last time but this Works On My Machine(tm).

Java / Swing app fails to transition to fullscreen on OS X

I'm using a JOGL FPSAnimator and Apple's FullScreenUtilies class. I implemented this some time ago, and it worked fine. Here is my code for enabling the native OS X fullscreen capability, similar to other code on SO and around the web:
String className = "com.apple.eawt.FullScreenUtilities";
String methodName = "setWindowCanFullScreen";
try {
Class<?> clazz = Class.forName(className);
Method method = clazz.getMethod(methodName,
new Class<?>[] { Window.class, boolean.class });
method.invoke(null, frame, true);
} catch ...
It also works fine in the context of a simple test program I made in an attempt to isolate the issue. I'm not sure at what point the behaviour changed - I haven't spotted anything incriminating in SVN logs. It's likely that I first implemented the feature on an earlier version of OS X, and have also upgraded JOGL version and MyDoggy which we use for docking since. However, all of these things work with fullscreen in the context of other applications.
When I press the green fullscreen button, the usual OSX fullscreen transition starts (it gets its own desktop space), but the window appears frozen from that point on.
The main AWT Event thread carries on running, and I can see that my GLEventListener.display() method is being regularly called. I've tried adding a return to the beginning of that method to eliminate the impact of my rendering code, this unsurprisingly made no difference.
For testing purposes, I added a FullScreenListener:
FullScreenUtilities.addFullScreenListenerTo(frame, new FullScreenAdapter() {
#Override
public void windowEnteringFullScreen(FullScreenEvent arg0) {
log(">>> Entering fullscreen... <<<");
}
#Override
public void windowEnteredFullScreen(FullScreenEvent arg0) {
log(">>> Entered fullscreen. <<<");
}
});
As anticipated, I get the entering fullscreen event, but not the entered one.
It's a fairly large program, but there should be a fairly small surface of things that are potentially relevant here... unfortunately I haven't managed to trace them down. Happy if anyone has any pointers.

How can I prevent the Charm bar from showing up in my Java application?

I've got a Java swing program that runs in full screen mode. It's effectively a kiosk program in that I want it to lock out everything else while it's running. This is running on a Windows 8.1 tablet, so of course the tablet is touchscreen, and therefore if you do an "edge swipe" (drag your finger from the right) the charms bar pops up and you can get to the Start screen from there. Is there some way to disable this from happening in Java? (Or is there some third-party solution not involving Java that can work in tandem to achieve the same result?)

You can disable edge gestures while your app is active and full screen by setting the System.EdgeGesture.DisableTouchWhenFullScreen property on the window.
I don't know if Java provides a direct way to set this (probably not), but you should be able to set this from a JNI.
Here's a C++ snippet from the DisableTouchWhenFullScreen docs:
HRESULT SetTouchDisableProperty(HWND hwnd, BOOL fDisableTouch)
{
IPropertyStore* pPropStore;
HRESULT hrReturnValue = SHGetPropertyStoreForWindow(hwnd, IID_PPV_ARGS(&pPropStore));
if (SUCCEEDED(hrReturnValue))
{
PROPVARIANT var;
var.vt = VT_BOOL;
var.boolVal = fDisableTouch ? VARIANT_TRUE : VARIANT_FALSE;
hrReturnValue = pPropStore->SetValue(PKEY_EdgeGesture_DisableTouchWhenFullscreen, var);
pPropStore->Release();
}
return hrReturnValue;
}

What I ended up doing was to write a batch script that kills explorer.exe and then re-spawns it after the app exits, based on this answer on Super User.

How to simulate a real mouse click using java?

I'm attempting to perform a mouse click in Java, to click something in an external program. To do this, I'm using java.awt.robot, and the following code:
Robot bot = new Robot();
int mask = InputEvent.MOUSE_BUTTON1_DOWN;
bot.mouseMove(x, y);
bot.mousePress(mask);
bot.mouseRelease(mask);
Here's the problem. The external program is able to detect that this click is computer-generated and not human-generated, and hence, its rejecting this click.
I have already tried moving the mouse there naturally and that didn't have any effect. So my guess is, that it must be listening to the keyboard state or such, and telling from that, that the click is computer generated.
What do I have to do to set all keyboard / mouse states to act in the same way as a normal mouse click would?

Well I had the same exact requirement, and Robot class is perfectly fine for me. It works on windows 7 and XP (tried java 6 & 7).
public static void click(int x, int y) throws AWTException{
Robot bot = new Robot();
bot.mouseMove(x, y);
bot.mousePress(InputEvent.BUTTON1_DOWN_MASK);
bot.mouseRelease(InputEvent.BUTTON1_DOWN_MASK);
}
May be you could share the name of the program that is rejecting your click?

FYI, in newer versions of Windows, there's a new setting where if a program is running in Adminstrator mode, then another program not in administrator mode, cannot send any clicks or other input events to it. Check your source program to which you are trying to send the click (right click -> properties), and see if the 'run as administrator' checkbox is selected.

it works in Linux. perhaps there are system settings which can be changed in Windows to allow it.
jcomeau#aspire:/tmp$ cat test.java; javac test.java; java test
import java.awt.event.*;
import java.awt.Robot;
public class test {
public static void main(String args[]) {
Robot bot = null;
try {
bot = new Robot();
} catch (Exception failed) {
System.err.println("Failed instantiating Robot: " + failed);
}
int mask = InputEvent.BUTTON1_DOWN_MASK;
bot.mouseMove(100, 100);
bot.mousePress(mask);
bot.mouseRelease(mask);
}
}
I'm assuming InputEvent.MOUSE_BUTTON1_DOWN in your version of Java is the same thing as InputEvent.BUTTON1_DOWN_MASK in mine; I'm using 1.6.
otherwise, that could be your problem.
I can tell it worked because my Chrome browser was open to http://docs.oracle.com/javase/7/docs/api/java/awt/Robot.html when I ran the program, and it changed to Debian.org because that was the link in the bookmarks bar at (100, 100).
[added later after cogitating on it today]
it might be necessary to trick the listening program by simulating a smoother mouse movement. see the answer here: How to move a mouse smoothly throughout the screen by using java?

With all respect the most likely thing is that you are mistaken about why the click is being 'rejected'. Why do you think some program is trying to determine if it's human or not? The Robot class (have used it a lot) should send messages that the operating system has no way to distinguish from a user doing the click.

Some applications may detect click source at low OS level. If you really need that kind of hack, you may just run target app in virtual machine's window, and run cliker in host OS, it can help.

You could create a simple AutoIt Script that does the job for you, compile it as an executable and perform a system call there.
in au3 Script:
; how to use: MouseClick ( "button" [, x, y [, clicks = 1 [, speed = 10]]] )
MouseClick ( "left" , $CmdLine[1], $CmdLine[1] )
Now find aut2exe in your au3 Folder or find 'Compile Script to .exe' in your Start Menu and create an executable.
in your Java class call:
Runtime.getRuntime().exec(
new String[]{
"yourscript.exe",
String.valueOf(mypoint.x),
String.valueOf(mypoint.y)}
);
AutoIt will behave as if it was a human and won't be detected as a machine.
Find AutoIt here: https://www.autoitscript.com/

Java TrayIcon.displayMessage() does not work on Windows XP

I'm writing an application that runs in the System Tray and notifies the user (i.e. makes one of those bubbles pop up) when something happens. The only problem is that the notifications only seem to work on Windows 7, and not Windows XP.
I've tested it on 2 Windows 7 computers (they've both worked) and 4 Windows XP computers (none of them have worked). No notification bubble is shown, and (as far as I know) no exceptions are thrown and everything else works as it should. I've even tested it on a Mac, and it worked, but it wasn't too pretty.
Here is a sample of my code.
private static TrayIcon trayIcon;
...
trayIcon = new TrayIcon(trayImage.getImage());
...
if (!SystemTray.isSupported())
{
System.out.println("SystemTray is not supported");
return;
}
final PopupMenu popup = new PopupMenu();
final SystemTray tray = SystemTray.getSystemTray();
trayIcon.setToolTip("Widget Name Here [" + role + "]");
...
try
{
tray.add(trayIcon);
}
catch (AWTException e)
{
System.err.println("TrayIcon could not be added.");
return;
}
...
//Here's where it doesn't work on XP
trayIcon.displayMessage("Connection error",
"Could not connect to server, please check your internet/VPN "
+ "connection", TrayIcon.MessageType.ERROR);
Any help would be much appreciated.
UPDATE: Ok, I've just confirmed that it's not a problem with my program, but a problem with the XP installations I've been testing them on. I ran the TrayIconDemo.java program found here on an XP computer and none of the notifications worked. I'm starting to think there's nothing I can do to get it to work on one of these computers...

Okay, so I've finally found the solution to my problem. It turned out that the following key was set to 0 (false) by default on the installations I was testing on:
HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced\EnableBalloonTips
To enable the notification bubbles, simply set the value to 1.

I have Windows XP and working on system tray application. I have just added displayMessage() and it works just fine for me. Try to simplify your application. I am sure it will work. The find a bug.

EDIT: you didn't mentioned JRE version System try required Java6
this should be comment, but this is restrict for chars lenght
maybe, there is another reason in case of when Java updates are distributed by some of administrations tool for AD or ZenWorks, then sometimes (on both win7/Xp) is needed un-install all java instalactions and install fresh JRE manually (but stable 1.6.022 my view), sw distibutions ends without error, but all (???) classes/methods/changes cames from Java6 weren't accesible, on partial (RowSorter etc...) test ends with error, and I never search for knows Bugs on MS, Novell ...