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What is java.awt.Component.getName() and setName() used for?

What is java.awt.Component.getName() used for? It always seems to be null in the applications I build with NetBeans. I'm thinking of storing some help text per component in it -- I don't want to use the tooltip, I have another panel where I'll show the help text.

How can I convert an Icon to an Image

I trying to convert an Icon (javax.swing.icon) to an Image (java.awt.Image) using this code :

private Image iconToImage(Icon icon)
{
    if(icon instanceof ImageIcon)
    {
        return ((ImageIcon) icon).getImage();
    }
    else
    {
        BufferedImage image = new BufferedImage(icon.getIconWidth(), icon.getIconHeight(), BufferedImage.TYPE_INT_RGB);
        icon.paintIcon(null, image.getGraphics(), 0, 0);
        return image;
    }
}

The thing is, the paintIcon function throws me a NullPointerException on the image.getGraphics().

For the record, the icon value is the default CheckBox icon (obtained via UIManager.getIcon("CheckBox.icon"))

Here's the details of the Exception thrown :

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
    at com.sun.java.swing.plaf.windows.WindowsIconFactory$CheckBoxIcon.paintIcon(WindowsIconFactory.java:306)
    at utils.WarningRenderer.iconToImage(WarningRenderer.java:50)
    at utils.WarningRenderer.<init>(WarningRenderer.java:38)
    at deliveryexpress.DeliveryExpressView.setWarnings(DeliveryExpressView.java:278)
    at deliveryexpress.DeliveryExpressView.updateLists(DeliveryExpressView.java:218)
    at deliveryexpress.DeliveryExpressView.access$1100(DeliveryExpressView.java:47)
    at deliveryexpress.DeliveryExpressView$5.addCheck(DeliveryExpressView.java:183)
    at org.japura.gui.model.DefaultListCheckModel.fireCheckListModelListeners(Unknown Source)
    at org.japura.gui.model.DefaultListCheckModel.fireAddCheckListModelListeners(Unknown Source)
    at org.japura.gui.model.DefaultListCheckModel.addCheck(Unknown Source)
    at org.japura.gui.CheckList$1.mouseClicked(Unknown Source)
    at java.awt.AWTEventMulticaster.mouseClicked(AWTEventMulticaster.java:253)
    at java.awt.Component.processMouseEvent(Component.java:6292)
    at javax.swing.JComponent.processMouseEvent(JComponent.java:3267)
    at java.awt.Component.processEvent(Component.java:6054)
    at java.awt.Container.processEvent(Container.java:2041)
    at java.awt.Component.dispatchEventImpl(Component.java:4652)
    at java.awt.Container.dispatchEventImpl(Container.java:2099)
    at java.awt.Component.dispatchEvent(Component.java:4482)
    at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4577)
    at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4247)
    at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4168)
    at java.awt.Container.dispatchEventImpl(Container.java:2085)
    at java.awt.Window.dispatchEventImpl(Window.java:2478)
    at java.awt.Component.dispatchEvent(Component.java:4482)
    at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:644)
    at java.awt.EventQueue.access$000(EventQueue.java:85)
    at java.awt.EventQueue$1.run(EventQueue.java:603)
    at java.awt.EventQueue$1.run(EventQueue.java:601)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlContext.java:87)
    at java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlContext.java:98)
    at java.awt.EventQueue$2.run(EventQueue.java:617)
    at java.awt.EventQueue$2.run(EventQueue.java:615)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlContext.java:87)
    at java.awt.EventQueue.dispatchEvent(EventQueue.java:614)
    at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:269)
    at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:184)
    at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:174)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:169)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:161)
    at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)

If you need more details, just tell me, I'll edit my post to add them.

Thanks !

Java: Getting resolutions of one/all available monitors (instead of the whole desktop)?

I have two different-sized monitors, connected together using (I believe) TwinView.

I tried

System.out.println(Toolkit.getDefaultToolkit().getScreenSize());

and get

java.awt.Dimension[width=2960,height=1050]

which is true if you count both monitors together.

Instead of this, I would like to be able achieving one of the following:

• getting resolution of the current monitor
• getting resolution of the main monitor

Is storing Graphics objects a good idea?

I'm currently in the process of writing a paint program in java, designed to have flexible and comprehensive functionalities. It stemmed from my final project, that I wrote overnight the day before. Because of that, it's got tons and tons of bugs, which I've been tackling one by one (e.g. I can only save files that will be empty, my rectangles don't draw right but my circles do...).

This time, I've been trying to add undo/redo functionality to my program. However, I can't "undo" something that I have done. Therefore, I got an idea to save copies of my BufferedImage each time a mouseReleased event was fired. However, with some of the images going to 1920x1080 resolution, I figured that this wouldn't be efficient: storing them would probably take gigabytes of memory.

The reason for why I can't simply paint the same thing with the background colour to undo is because I have many different brushes, which paint based on Math.random(), and because there are many different layers (in a single layer).

Then, I've considered cloning the Graphics objects that I use to paint to the BufferedImage. Like this:

ArrayList<Graphics> revisions = new ArrayList<Graphics>();

@Override
public void mouseReleased(MouseEvent event) {
    Graphics g = image.createGraphics();
    revisions.add(g);
}

I haven't done this before, so I have a couple questions:

• Would I still be wasting pointless memory by doing this, like cloning my BufferedImages?
• Is there necessarily a different way I can do this?

Load Icon Image Exception

I am having a error for my GUI. Trying to set title bar icon then be included in a Runnable JAR.

BufferedImage image = null;
try {
    image = ImageIO.read(getClass().getClassLoader().getResource("resources/icon.gif"));
} 
catch (IOException e) {
    e.printStackTrace();
}

frame.setIconImage(image);

Here is the error I am getting:

Exception in thread "main" java.lang.IllegalArgumentException: input == null!
    at javax.imageio.ImageIO.read(Unknown Source)
    at GUI.<init>(GUI.java:39)
    at GUI.main(GUI.java:351)

The image is in the correct directory which "resources" folder is the root of the project file

Is it safe to construct Swing/AWT widgets NOT on the Event Dispatch Thread?

I've been integrating the Substance look and feel into my application and ran into several problems regarding it's internal EDT (Event Dispatch Thread) checking routines. Substance absolutely refuses to construct UI classes outside of the EDT. I've done plenty of Swing/AWT and I know most of the rules regarding the EDT. I use SwingWorker, SwingUtilties.invokeLater to modify components. I always though that components could be CONSTRUCTED outside of the EDT, but must be realized and manipulated on the EDT. In other words, you can construct and setup defaults in the background but the call to pack/setVisible must be EDT as well as any subsequent calls to manipulate the component.

The reason I ask is that I have a particularly "beefy" window to construct, involving many widgets, state, and resources (lots of icons). Previously, I constructed the window on the background method of a SwingWorker and made the window visible in the done method. Never had a single problem. Upon switching to Substance, the internal EDT checking bites me.

I've been able to refactor code to get around this. I can construct on the EDT which isn't a good solution since the entire application will block. I can also refactor even more and try my best to load all of the extra resources outside of the EDT.

Wrapping it up ... Is it safe to construct Swing/AWT widgets NOT on the Event Dispatch Thread?

"Always on Top" Windows with Java

In Java, is there a way to have a window that is "Always on top" regardless if the user switches focus to another application? I've searched the web, and all of the solutions lean to some sort of JNI interface with native bindings. Truly this can't be the only way to do it?.. or is it?

Fake X11 display?

I have a Java program using AWT which I would like to run on a headless system. The display for the program does nothing other than display stats. When the program finishes, it exits. There is no user interaction on the display. The program creates an output file which I use in my build system.

Is there a way to get the Java program to run without an X11 display configured? Can I force Java to run the program without trying to display anything? I do not have access to the source code (it is just .jar file), so I can't make modifications to the source.

Any thoughts on how I could get this to work?

Is Java Swing still in use?

I am planning on making a Java Swing application and was wondering if Swing is still used or if it has been replaced with something else.

Thanks in advance!

Setting java.awt.headless=true programmatically

I'm trying to set java.awt.headless=true during the application startup but it appears like I'm too late and the non-headless mode is already started:

static {
    System.setProperty("java.awt.headless", "true");
    /* java.awt.GraphicsEnvironment.isHeadless() returns false */
}

Is there another way set headless to true beside -Djava.awt.headless=true? I would prefer to not configure anything on the console.

Copying to Clipboard in Java

I want to set the users clipboard to a string in a Java Console Application. Any ideas?

Java Event-Dispatching Thread explanation

I've recently started learning and exploring the basics of GUI programming in Java.

Having been programming for a while I have only done backend work or work and as a result the closest I've gotten to user interfaces is the command console (embarrassing I know).

I'm using Swing and as far as I can gather that means by extension I am also using AWT.

My question is based on this piece of code:

java.awt.EventQueue.invokeLater(new Runnable() {
    public void run() {
        new frame.setVisible(true);
    }
} );

I have been researching this for a while as I wanted to fully understand this strange piece of code and have come across the term 'Event-Dispatching Thread' multiple times. Correct me if I'm wrong but as I understand it; it has to do with using multiple threads and how Java Swing interprets those threads. I gather as well that the above code is used to make sure all the threads are 'safe' before it creates the window, hence the invokeLater?

I have read that:

"You can only call methods that operate on the frame from the Event-Dispatching Thread"

and that only under certain circumstances can you call methods that operate on the frame from the main method.

Can somebody please clarify to me what exactly the Event-Dispatching Thread is? How it relates to multiple threads of execution and how those threads are not safe to be called from the main method? Also why do we need this invokeLater? Can we not just create the window as any other object?

I've hit a bit of a road block in my research as I'm not grasping these relations and ideas.

A side note is that I like to base my knowledge on in-depth understanding as I believe this leads to the best overall outcome and as a result the best programs. If I understand in-depth how something works then you can use the tips and tweaks effectively rather than just parroting them back in to code, so please don't be afraid to give me some extra in-depth explanations and broaden my knowledge.

Thank you.

Java: using an image as a button

I would like to use an image as a button in Java, and I tried to do this:

BufferedImage buttonIcon = ImageIO.read(new File("buttonIconPath"));
button = new JButton(new ImageIcon(buttonIcon));

But this still shows the actual button behind the image, I would only like the image to function as the button, how can I do this?

Thanks in advance.

EDIT: SOLUTION FOUND

A combination of jzd answer and something else I found solved the problem:

button.setBorder(BorderFactory.createEmptyBorder());
button.setContentAreaFilled(false);

This did the trick for me, thanks for your answers!

SwingUtilities.invokeLater

My question is related to SwingUtilities.invokeLater. When should I use it? Do I have to use each time I need to update the GUI components? What does it exactly do? Is there an alternative to it since it doesn't sound intuitive and adds seemingly unnecessary code?

How to center a Window in Java?

What's the easiest way to centre a java.awt.Window, such as a JFrame or a JDialog?