I'm making a simple program of a PONG game, and my problem comes from the Main method which i wanted to set an image icon and it shoots me a NullPointerException.
I'm working with Eclipse IDE 2019,06 and the Java Compiler 12.0.1. The image that I am using is .jpg.
I've tried to change the directory of the image and nothing :(.
The directory of the image is in a folder which is in the same folder of the main class.
This is my frame code:
public class Menu {
private JFrame frame;
/**
* Launch the application.
*/
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
public void run() {
try {
Menu window = new Menu();
window.frame.setVisible(true);
window.frame.setLocationRelativeTo(null);
window.frame.setTitle("PONG!");
} catch (Exception e) {
e.printStackTrace();
}
}
});
}
/**
* Create the application.
*/
public Menu() {
frame.setIconImage(new ImageIcon(Menu.class.getResource("/icon.jpg")).getImage());
initialize();
}
So this is the error message:
java.lang.NullPointerException
at javax.swing.ImageIcon.<init>(Unknown Source)
at gui.Menu.<init>(Menu.java:57)
at gui.Menu$1.run(Menu.java:42)
at java.awt.event.InvocationEvent.dispatch(Unknown Source)
at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
at java.awt.EventQueue.access$500(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)
I hope you can help me with this problem. Thanks.
I guess line 57 of Menu.java is this line:
frame.setIconImage(new ImageIcon(Menu.class.getResource("/icon.jpg")).getImage());
It looks like frame has not been initialized and therefore is null. That's why you get a NullPointerException.
When you work with the Maven build system (e.g. netbeans 11.3, maven 3.3.x), you have to take care where you place your resources. The "/icon.jpg" path is relative to your resources directory. Try to create a directory named "resources" (sic!) as a subdirectory of the java main source directory. For example, the path to "resources" should be
<Project root>/src/main/resources
You place your image files in this directory or a maybe a subdirectory /src/main/resources/icons/icon.jpg
Related
I have a NullPointerException in my application, that happens only on one specific PC, and is reproducible. I wrote my GUI using Javafx with some Swing JPanels on it via SwingNode.
What should I do?
Exception-Time = 2016-08-30 06:55:50 UTC Exception-Tag = 0 Exception-Message = Thread AWT-EventQueue-0 (Id = 55) throw exception: null Stack-Trace = java.lang.NullPointerException
at sun.swing.JLightweightFrame.updateClientCursor(Unknown Source)
at sun.swing.JLightweightFrame.access$000(Unknown Source)
at sun.swing.JLightweightFrame$1.updateCursor(Unknown Source)
at sun.awt.windows.WLightweightFramePeer.updateCursorImmediately(Unknown Source)
at java.awt.Component.updateCursorImmediately(Unknown Source)
at java.awt.Container.validate(Unknown Source)
at java.awt.Window.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
at java.awt.EventQueue.access$500(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Unknown Source)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue$4.run(Unknown Source)
at java.awt.EventQueue$4.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)
More about the problem:
Apparently, this is a bug at the JDK itself (versions 8 and 9) and probably won't get fixed until JDK10.
This exception is thrown from within the sun.swing.JLightweightFrame.java class, at the updateClientCursor function (lines 472-749):
private void updateClientCursor() {
Point p = MouseInfo.getPointerInfo().getLocation();
SwingUtilities.convertPointFromScreen(p, this);
Component target = SwingUtilities.getDeepestComponentAt(this, p.x, p.y);
if (target != null) {
content.setCursor(target.getCursor());
}
}
In general, this is happening because MouseInfo.getPointerInfo() can return NULL, for example, when you move between graphic devices. 'MouseInfo' can still hold the former graphic device information, then getPointerInfo() can return NULL if the mouse already moved to the new graphic device and MouseInfo still didn't updated to the new graphic device information. this scenario will cause a Null Pointer Exception on this line MouseInfo.getPointerInfo().getLocation() for trying to run a method of a NULL object.
For me, NPE is thrown when I move my JavaFX app window between monitors on my multiscreen machine. Its not happening every time but it is reproducible very easily.
I'm using a Swing component in a JavaFX SwingNode component.
This bug is already a known issue at Oracle bug list.
Code Fix:
This snippet shows an optional fix for this bug:
private void updateClientCursor() {
PointerInfo pointerInfo = MouseInfo.getPointerInfo();
if (pointerInfo == null) {
/*
* This can happen when JavaFX cannot decide
* which graphics device contains the current
* mouse position.
*/
return;
}
Point p = pointerInfo.getLocation();
SwingUtilities.convertPointFromScreen(p, this);
Component target = SwingUtilities.getDeepestComponentAt(this, p.x, p.y);
if (target != null) {
content.setCursor(target.getCursor());
}
}
Taken from JetBrains repository
Optional solution:
Since it is a bug withing the formal Oracle JDK, there is no much I can do about it. there are fixes applied in other non-formal JDKs like OpenJDK for example, which applied a fix, but I don't know which version will apply this fix yet.
For me, I would probably try to compile and use my own JDK with the applied fix and use it in my project, but this is a hard to maintain and not so flexible solution. If someone have another fix/workaround I would be happy to hear.
Googling a lot, I found nothing about the problem with this specific class (Key.Adapter.class), but there are a lot of topics about rt.jar of course, and I tried so many things to correct it, I tried to set the location of rt.jar and installed the plugin Java Source Attacher (didn't work). I reinstalled Eclipse as well, but the error still occurs:
What's strange about this is that I didn't make any change at anything related to the library (if I did, that was not intentional). I was just moving some things but nothing related to the libraries. The console returns NullPointerException at line 190:
name2.addKeyListener(new KeyAdapter() {
#Override
public void keyPressed(KeyEvent arg0) {
int key = arg0.getKeyCode();
if (key == KeyEvent.VK_ESCAPE) {
//Custom button text
Object[] options = {"Sim",
"Não"};
int choice = JOptionPane.showOptionDialog(frame1,
"Deseja sair do jogo?",
"Mensagem",
JOptionPane.YES_NO_CANCEL_OPTION,
JOptionPane.QUESTION_MESSAGE,
null,
options,
options[1]);
if (choice == 0) {
System.exit(0);
}
}
}
}
);
To make a new project will be that way as well. And the Window Designer / Run doesn't work as well.
Is there another possibility to make rt.jar useful again?
java.lang.NullPointerException
at view.Main.<init>(Main.java:191)
at view.Main$1.run(Main.java:49)
at java.awt.event.InvocationEvent.dispatch(Unknown Source)
at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
at java.awt.EventQueue.access$500(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)
I wonder about a Java error that is repeatedly occurs in MATLAB. It typically occurs when MATLAB is doing some heavy stuff with Java. This can for example be holding Ctrl + Z or Ctrl + Y.
I did by mistake erase the error message before I copied it, but I think that I can pass the core of the problem anyway.
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
...
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)
Why did this error occur? I have found some information about this from MATLAB r2007, this due to that Java Swing is thread unsafe and MATLAB lacked support to ensure thread safety. However, that is supposed to have been fixed in MATLAB r2008b. So why do I get it now?
Here is the full stack trace:
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at org.netbeans.editor.BaseDocument.notifyUnmodify(BaseDocument.java:1465)
at org.netbeans.editor.BaseDocument.notifyModifyCheckEnd(BaseDocument.java:816)
at org.netbeans.editor.BaseDocumentEvent.redo(BaseDocumentEvent.java:336)
at javax.swing.undo.UndoManager.redoTo(Unknown Source)
at javax.swing.undo.UndoManager.redo(Unknown Source)
at com.mathworks.mwswing.undo.MUndoManager.redo(MUndoManager.java:255)
at org.netbeans.editor.ActionFactory$RedoAction.actionPerformed(ActionFactory.java:767)
at org.netbeans.editor.BaseAction.actionPerformed(BaseAction.java:259)
at javax.swing.SwingUtilities.notifyAction(Unknown Source)
at javax.swing.JComponent.processKeyBinding(Unknown Source)
at javax.swing.JComponent.processKeyBindings(Unknown Source)
at javax.swing.JComponent.processKeyEvent(Unknown Source)
at com.mathworks.widgets.SyntaxTextPaneBase.processKeyEvent(SyntaxTextPaneBase.java:1187)
at java.awt.Component.processEvent(Unknown Source)
at java.awt.Container.processEvent(Unknown Source)
at java.awt.Component.dispatchEventImpl(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.KeyboardFocusManager.redispatchEvent(Unknown Source)
at java.awt.DefaultKeyboardFocusManager.dispatchKeyEvent(Unknown Source)
at java.awt.DefaultKeyboardFocusManager.preDispatchKeyEvent(Unknown Source)
at java.awt.DefaultKeyboardFocusManager.typeAheadAssertions(Unknown Source)
at java.awt.DefaultKeyboardFocusManager.dispatchEvent(Unknown Source)
at java.awt.Component.dispatchEventImpl(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Window.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)
Well, based on your stack trace, probably there isn’t any definitive answer to your question, as you have already seen in MATLAB's forum, but given this line, I think there's a possible explanation:
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
...
at javax.swing.undo.UndoManager.redoTo(Unknown Source) // <-- here!
at javax.swing.undo.UndoManager.redo(Unknown Source)
at com.mathworks.mwswing.undo.MUndoManager.redo(MUndoManager.java:255)
...
UndoManager class keeps an internal collection of UndoableEdit objects. This collection is actually inherithed from its superclass: CompoundEdit.
The internal implementation of UndoManager#redo() and UndoManager#redoTo(UndoableEdit edit) looks like this:
public class UndoManager extends CompoundEdit implements UndoableEditListener {
...
public synchronized void redo() throws CannotRedoException {
if (inProgress) {
UndoableEdit edit = editToBeRedone();
if (edit == null) {
throw new CannotRedoException();
}
redoTo(edit);
} else {
super.redo();
}
}
...
protected void redoTo(UndoableEdit edit) throws CannotRedoException {
boolean done = false;
while (!done) {
UndoableEdit next = edits.elementAt(indexOfNextAdd++);
next.redo(); // NPE here?
done = next == edit;
}
}
...
}
Considering this implementation and given that Swing's Event Dispatch Thread (EDT) is prone to cause troubles, I think it's probably a threading issue between MATLAB threads and the EDT. Specifically speaking this MATLAB-invoked method could be the source of the problem:
at com.mathworks.mwswing.undo.MUndoManager.redo(MUndoManager.java:255)
Since you say MATLAB needs to do heavy work, it's not unreasonable to think this method is trying to redo some edit that might well not be available anymore or might not be available yet, due to synchronization problems with the EDT.
You can find the ~/.matlab folder which contains MATLAB settings, etc. Use ls -la to show all hidden files and folders.
Open a terminal and execute sudo chmod 757 -R ~/.matlab.
Similarly there is a folder, MATLAB, in Documents.
Execute sudo chmod 757 -R ~/Documents/MATLAB.
Now restart MATLAB without root privileges. It worked for me on Ubuntu 14.04 (Trusty Tahr) and MATLAB 2015a.
I've built this actionPerformed method so that it reads a string I pass to the button (I needed to make my own button class to hold this new string) and depending on what it says, it does a different action. One of the possibilities of the string is to be something like: shell(""). This is supposed to run a system command (command line in windows, shell command in unix/linux) in the background. This is the source of the method:
public void actionPerformed(ActionEvent e) {
if (e.getSource() == this.button) {
if (password != "") {
}
if (action.startsWith("shell(\"")) {
String tmpSHELL = action.substring(7, action.length() - 2);
try {
Process p = Runtime.getRuntime().exec(tmpSHELL);
} catch (IOException e1) {
ErrorDialog error = new ErrorDialog("Error handling your shell action");
System.exit(0);
}
}
else if (action.startsWith("frame(\"")) {
String tmpFRAME = action.substring(7, action.length() - 2);
MenuFrame target = ConfigReader.getFrame(tmpFRAME);
this.parent.setVisible(false);
this.parent.validate();
target.setVisible(true);
target.validate();
}
else if (action.equals("exit()")) {
System.exit(0);
}
else {
ErrorDialog error = new ErrorDialog("You config file contains an invalid action command. Use either shell(), frame() or exit()");
System.exit(0);
}
}
}
I know that I get into the method but I'm not sure if the command is being executed successfully. I'm currently in a windows environment so I made a simple batch script that echos some text then waits for a keystroke before printing the tree of the C: drive. I put the .bat into my working java directory and passed the string shell("test") (test is the name of the batch file). However, when I click the button I get an error dialog (the one I coded above).
Is there something wrong with my code or maybe my understanding of how executing a shell command works in java? The command is throwing an IO exception but I can't seem to figure out why. Thanks in advance for your help.
Stacktrace:
java.io.IOException: Cannot run program "test": CreateProcess error=2, The system cannot find the file specified
at java.lang.ProcessBuilder.start(Unknown Source)
at java.lang.Runtime.exec(Unknown Source)
at java.lang.Runtime.exec(Unknown Source)
at java.lang.Runtime.exec(Unknown Source)
at Button.actionPerformed(Button.java:52)
at javax.swing.AbstractButton.fireActionPerformed(Unknown Source)
at javax.swing.AbstractButton$Handler.actionPerformed(Unknown Source)
at javax.swing.DefaultButtonModel.fireActionPerformed(Unknown Source)
at javax.swing.DefaultButtonModel.setPressed(Unknown Source)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(Unknown Source)
at java.awt.Component.processMouseEvent(Unknown Source)
at javax.swing.JComponent.processMouseEvent(Unknown Source)
at java.awt.Component.processEvent(Unknown Source)
at java.awt.Container.processEvent(Unknown Source)
at java.awt.Component.dispatchEventImpl(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.LightweightDispatcher.retargetMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.processMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.dispatchEvent(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Window.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)
Caused by: java.io.IOException: CreateProcess error=2, The system cannot find the file specified
at java.lang.ProcessImpl.create(Native Method)
at java.lang.ProcessImpl.<init>(Unknown Source)
at java.lang.ProcessImpl.start(Unknown Source)
... 30 more
The system cannot find the file specified
Your file path is not right. Try passing an absolute file path.
shell("C:/somedirectory/test.bat")
Also, you can test this by removing the string test altogether. Hard code the runtime execution of the batch file by making the if statement always true and passing the path to your batch file to the Runtime.getRuntime().exec()
if (password != "") {
}
if (true) {
String tmpSHELL = action.substring(7, action.length() - 2);
try {
Process p = Runtime.getRuntime().exec("test");
} catch (IOException e1) {
ErrorDialog error = new ErrorDialog("Error handling your shell action");
System.exit(0);
}
}
This should produce the same error. Then replace the file path with an absolute file path and you should be able to execute the batch file.
Process p = Runtime.getRuntime().exec("C:/somedirectory/test.bat");
On Windows try command line:
"cmd test /c"
It's because the command test isn't found in the system PATH environment variable.
If you go to the command line and type test it will fail. This is what the exception is indicating.
My program downloads a websites source code, modifies it, creates the file, and then reuploads it through the FTP. However, I receive the following error when trying to open the created file:
java.io.FileNotFoundException: misc.html (Access is denied)
at java.io.FileInputStream.open(Native Method)
at java.io.FileInputStream.<init>(Unknown Source)
at Manipulator.uploadSource(Manipulator.java:63)
at Start.addPicture(Start.java:130)
at Start$2.actionPerformed(Start.java:83)
at javax.swing.AbstractButton.fireActionPerformed(Unknown Source)
at javax.swing.AbstractButton$Handler.actionPerformed(Unknown Source)
at javax.swing.DefaultButtonModel.fireActionPerformed(Unknown Source)
at javax.swing.DefaultButtonModel.setPressed(Unknown Source)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(Unknown Source)
at java.awt.Component.processMouseEvent(Unknown Source)
at javax.swing.JComponent.processMouseEvent(Unknown Source)
at java.awt.Component.processEvent(Unknown Source)
at java.awt.Container.processEvent(Unknown Source)
at java.awt.Component.dispatchEventImpl(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.LightweightDispatcher.retargetMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.processMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.dispatchEvent(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Window.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)
When I navigate to the folder directory and attempt to open "misc.html" with Notepad I receive Access is Denied. My code is fairly simple:
File f = new File(page.sourceFileName);
try {
FileWriter out = new FileWriter(f);
out.write(page.source);
out.close();
} catch (IOException e) {
e.printStackTrace();
} InputStream input = new FileInputStream(f);
This is the vital excerpt from my program. I have copied this into a different test program and it works fine, I create a misc.html file and reopen it with both FileInputStream and manually.
I would be worried about Administrator rights but the Test program works fine when I run it RIGHT after the problem program. I also have checked if the file exists and is a file with File methods and it is as well. Is this a result of me not closing a previous Input/Output properly? I've tried to check everything and I am fairly positive I close all streams as soon as they finish...
Help! :)
UPDATE:
If I comment out the FileInputStream code and just leave the FileWriter the File still is Access Denied. If I remove the FileWriter code, no File is made (so it's certainly not overwriting anything). The FileWriter code is the first time the file is made and no exception is thrown - but I still cannot manually open the file.
If you really have sufficient permissions to read that file, then the thing I can notice is that you are not using streams properly:
out.write(page.source); // if this throws an exception
out.close(); //this is not called, and the file remains open
You must close the streams in a finally block.
FileWriter fw = null;
try {
fw = new FileWriter(f);
fw.write(page.source);
} catch (IOException ex) {
ex.printStackTrace(); //consider a logger
} finally {
IOUtils.closeQuietly(fw);
}
The same goes for the InputStreams
Now, the IOUtils.closeQuietly(fw) is a bit controversial, since it will not report an exception that happens during the closing of a file. And it is from apache commons-io (external dependency). You can replace it with another try-catch inside the finally and then a null check, before calling close(). Luckily this will be a lot easier in Java 7.
This kind of error seems to happen when trying to work on a directory. Sure you don't?
Make some extra log output what you open and close, and return here....
Does your program run in as an Applet or WebStart application? If so, it is likely that the JVM sandbox is preventing your (untrusted) code from accessing the local filesystem.