Thursday, October 29, 2015

Install java-gnome on Ubuntu 15.10, and first try.

The java-gnome User Interface Library is a Java bindings for GTK and GNOME. To install it on Ubuntu, enter the command in Terminal:
$ sudo apt-get install libjava-gnome-java


First try:

Create a my first example (copt from HERE), under trial directory ~/java-gnome-works.
 * Copyright (c) 2006-2008 Operational Dynamics Consulting Pty Ltd
 * The code in this file, and the library it is a part of, are made available
 * to you by the authors under the terms of the "GNU General Public Licence,
 * version 2" See the LICENCE file for the terms governing usage and
 * redistribution.
package button;

import org.gnome.gdk.Event;
import org.gnome.gtk.Button;
import org.gnome.gtk.Gtk;
import org.gnome.gtk.Label;
import org.gnome.gtk.VBox;
import org.gnome.gtk.Widget;
import org.gnome.gtk.Window;

 * A simple Window with a Label and a Button in it. Demonstrates the basics of
 * initializing GTK, packing Widgets into Containers, and hooking up signals.
 * This example has been around, in one form or another, since the very
 * beginnings of java-gnome. If you're just starting out with GTK and GNOME
 * don't worry; we started here too.
 * @author Andrew Cowie
 * @since 4.0.0
public class ExamplePressMe
    public static void main(String[] args) {
        final Window w;
        final VBox x;
        final Label l;
        final Button b;

         * Initialize GTK. You MUST call this to load the library before
         * trying to use any other elements provided by java-gnome.


         * Create a top level Window. It's the Container around which the
         * window manager draws decorations such as a title bar, minimize and
         * close buttons, resize edges, etc.

        w = new Window();

         * Since a Window is a Bin, it can only have one child Widget. That's
         * probably not very useful in most cases. To take that one slot and
         * turn it into many, we use a VBox, a Container that will stack its
         * children vertically.

        x = new VBox(false, 3);

         * Create a Label with some text describing the Button that will
         * follow, then add it to the VBox.

        l = new Label("Go ahead:\nMake my day");

         * Create our Button, with a nice explicit bit of text labelling it
         * and what you're to do.

        b = new Button("Press me!");

         * Now the magic part. Just sitting there, the Button won't do
         * anything. You need to hook up a "signal handler" to deal with the
         * 'clicked' signal. This is how we do it in java-gnome.
         * Button.Clicked is a Java interface. You create an instance of it to
         * do what you want when the callback happens, and then pass it to the
         * Button's connect() method.
         * The onClicked() method is what is required by the Button.Clicked
         * interface. Most IDEs will prompt you asking if you want to "Add
         * unimplemented methods?" You bet! And ta-da! You have exactly the
         * signature you need to implement a 'clicked' signal handler.
         * Since we declared b as final we can use it in the anonymous nested
         * class (yet *another* reason that final is worth using). If the
         * situation were otherwise, then the source parameter can be used to
         * find out what Button was clicked.

        b.connect(new Button.Clicked() {
            public void onClicked(Button source) {
                System.out.println("I was clicked: " + b.getLabel());

         * Now we pack the VBox into our Window, set the Window's title, and
         * invoke the command to realize everything onto the screen.

        w.setTitle("Hello World");

         * We would be be done except for one last detail. Closing a Window
         * does not terminate the application. If that's what you want (and we
         * do indeed want that here) then you need to hook up a handler to do
         * something when the 'delete-event' signal is emitted.
         * Again, the method here implements the interface.

        w.connect(new Window.DeleteEvent() {
            public boolean onDeleteEvent(Widget source, Event event) {
                return false;

         * Now we're ready to run the main loop. The signals we've hooked up
         * handlers for above won't be emitted until the user does something,
         * but no events will be processed until the main loop is running;
         * that's where the signals will come from. This call blocks. You have
         * finished setting things up and now it's up to your signal handlers
         * to carry out the program's logic in response to the user's actions;
         * the essence of event-driven programming.


Make a tests directory to hold the output.

Enter the command to compile the java code with java-gnome.
$ javac -classpath /usr/share/java/gtk-4.1.jar -d tests

Run it:
$ java -classpath /usr/share/java/gtk-4.1.jar:tests button.ExamplePressMe

Where /usr/share/java/gtk-4.1.jar is the installed gtk-4.1.jar.


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