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| - | In this part of the Java Gnome programming tutorial, we will talk about events.
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| - | __TOC__
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| - |
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| - | Java Gnome library is an event driven system. All GUI applications are event driven.
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| - | The applications start a main loop, which continuously checks for newly generated events. If there is no event, the application waits and does nothing.
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| - |
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| - | == Simple event example ==
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| - |
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| - | The next example shows, how we react to two basic events.
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| - | <source lang="java">
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| - | package com.zetcode;
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| - | import org.gnome.gdk.Event;
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| - | import org.gnome.gtk.Button;
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| - | import org.gnome.gtk.Fixed;
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| - | import org.gnome.gtk.Gtk;
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| - | import org.gnome.gtk.Widget;
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| - | import org.gnome.gtk.Window;
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| - | import org.gnome.gtk.WindowPosition;
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| - |
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| - | /**
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| - | * Java Gnome tutorial
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| - | *
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| - | * This program demonstrates two
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| - | * basic events.
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| - | *
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| - | * @author jan bodnar
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| - | * website zetcode.com
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| - | * last modified March 2009
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| - | */
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| - | public class GButton extends Window {
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| - | public GButton() {
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| - |
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| - | setTitle("Button");
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| - |
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| - | initUI();
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| - | setPosition(WindowPosition.CENTER);
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| - | showAll();
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| - | }
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| - | public void initUI() {
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| - | connect(new Window.DeleteEvent() {
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| - | public boolean onDeleteEvent(Widget source, Event event) {
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| - | Gtk.mainQuit();
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| - | return false;
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| - | }
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| - | });
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| - | Fixed fixed = new Fixed();
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| - | Button quit = new Button("Quit");
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| - | quit.connect(new Button.Clicked() {
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| - | public void onClicked(Button button) {
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| - | Gtk.mainQuit();
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| - | }
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| - | });
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| - | quit.setSizeRequest(80, 35);
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| - | fixed.put(quit, 50, 50);
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| - | add(fixed);
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| - | setSizeRequest(250, 200);
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| - | }
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| - | public static void main(String[] args) {
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| - | Gtk.init(args);
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| - | new GButton();
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| - | Gtk.main();
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| - | }
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| - | }
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| - | </source>
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| - | In our code example, we react to two events. Delete event and click event.
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| - | The delete event is triggered, when we close the window. By default, the window is destroyed but the application does not quit. We must explicitely quit the program.
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| - | <source lang="java">
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| - | connect(new Window.DeleteEvent() {
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| - | public boolean onDeleteEvent(Widget source, Event event) {
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| - | Gtk.mainQuit();
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| - | return false;
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| - | }
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| - | });
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| - | </source>
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| - |
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| - | If we click on the close button of the window, the window is destroyed.
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| - | But the application is not fully destroyed. We must call the <b>Gtk.mainQuit()</b> to end the application.
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| - | We use the <b>connect()</b> method to connect a callback method to a specific event type. In our case it is the <b>DeleteEvent</b>.
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| - | <source lang="java">
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| - | quit.connect(new Button.Clicked() {
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| - | public void onClicked(Button button) {
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| - | Gtk.mainQuit();
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| - | }
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| - | });
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| - | </source>
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| - | When we click on the button widget, the <b>onClicked()</b> method is triggered. We quit the application in reaction to the button click.
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| - |
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| - | == Moving window ==
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| - | The next example shows, how we react to move events of a window.
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| - | We show the current position of the upper left corner of the window in the titlebar.
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| - | <source lang="java">
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| - | package com.zetcode;
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| - | import org.gnome.gdk.Event;
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| - | import org.gnome.gdk.EventConfigure;
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| - | import org.gnome.gtk.Gtk;
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| - | import org.gnome.gtk.Widget;
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| - | import org.gnome.gtk.Window;
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| - | import org.gnome.gtk.WindowPosition;
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| - |
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| - | /**
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| - | * ZetCode Java Gnome tutorial
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| - | *
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| - | * This program demonstrates the
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| - | * configure event.
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| - | *
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| - | * @author jan bodnar
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| - | * website zetcode.com
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| - | * last modified March 2009
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| - | */
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| - | public class GMoveWindow extends Window
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| - | implements Window.ConfigureEvent {
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| - | public GMoveWindow() {
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| - |
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| - | connect(new Window.DeleteEvent() {
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| - | public boolean onDeleteEvent(Widget source, Event event) {
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| - | Gtk.mainQuit();
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| - | return false;
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| - | }
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| - | });
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| - |
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| - | connect(this);
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| - |
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| - | setPosition(WindowPosition.CENTER);
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| - |
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| - | setTitle("");
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| - | resize(250, 200);
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| - | showAll();
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| - | }
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| - | public boolean onConfigureEvent(Widget widget,
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| - | EventConfigure eventConfigure) {
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| - | int x = eventConfigure.getX();
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| - | int y = eventConfigure.getY();
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| - |
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| - | setTitle(x + ", " + y);
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| - | return false;
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| - | }
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| - | public static void main(String[] args) {
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| - | Gtk.init(args);
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| - | new GMoveWindow();
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| - | Gtk.main();
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| - | }
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| - | }
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| - | </source>
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| - | Resizing and moving windows end up in <b>ConfigureEvent</b> being created.
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| - | <source lang="java">
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| - | public boolean onConfigureEvent(Widget widget,
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| - | EventConfigure eventConfigure) {
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| - | int x = eventConfigure.getX();
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| - | int y = eventConfigure.getY();
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| - | setTitle(x + ", " + y);
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| - | return false;
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| - | }
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| - | </source>
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| - | We set the x, y coordinates of the window to the titlebar of the window.
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| - | [[image: Java_Gnome_faq_move.png| center]]
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| - | == EnterNotifyEvent ==
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| - | <b>EnterNotifyEvent</b> is emitted, when we enter the area of a widget with a mouse pointer.
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| - |
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| - | <source lang="java">
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| - | package com.zetcode;
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| - | import org.gnome.gdk.Color;
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| - | import org.gnome.gdk.Event;
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| - | import org.gnome.gdk.EventCrossing;
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| - | import org.gnome.gtk.Button;
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| - | import org.gnome.gtk.Fixed;
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| - | import org.gnome.gtk.Gtk;
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| - | import org.gnome.gtk.StateType;
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| - | import org.gnome.gtk.Widget;
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| - | import org.gnome.gtk.Window;
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| - | import org.gnome.gtk.WindowPosition;
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| - |
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| - | /**
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| - | * ZetCode Java Gnome tutorial
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| - | *
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| - | * This program demonstrates the
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| - | * EnterNotifyEvent.
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| - | *
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| - | * @author jan bodnar
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| - | * website zetcode.com
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| - | * last modified March 2009
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| - | */
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| - | public class GEnterNotifyEvent extends Window {
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| - | private Color lightGray = new Color(55000, 55000, 55000);
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| - | public GEnterNotifyEvent() {
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| - | setTitle("EnterNotifyEvent");
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| - | initUI();
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| - | connect(new Window.DeleteEvent() {
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| - | public boolean onDeleteEvent(Widget source, Event event) {
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| - | Gtk.mainQuit();
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| - | return false;
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| - | }
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| - | });
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| - |
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| - | setDefaultSize(250, 150);
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| - | setPosition(WindowPosition.CENTER);
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| - | showAll();
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| - | }
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| - |
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| - | public void initUI() {
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| - |
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| - | Button button = new Button("Button");
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| - | button.setSizeRequest(80, 30);
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| - | button.connect(new Button.EnterNotifyEvent() {
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| - | public boolean onEnterNotifyEvent(Widget widget,
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| - | EventCrossing eventCrossing) {
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| - | widget.modifyBackground(StateType.PRELIGHT, lightGray);
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| - |
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| - | return false;
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| - | }
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| - | });
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| - |
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| - | Fixed fix = new Fixed();
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| - | fix.put(button, 20, 20);
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| - | add(fix);
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| - | }
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| - | public static void main(String[] args) {
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| - | Gtk.init(args);
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| - | new GEnterNotifyEvent();
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| - | Gtk.main();
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| - | }
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| - | }
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| - | </source>
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| - | We will change the background color of the button widget, once we hover a mouse pointer over it.
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| - |
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| - | <source lang="java">
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| - | button.connect(new Button.EnterNotifyEvent() {
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| - | public boolean onEnterNotifyEvent(Widget widget,
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| - | EventCrossing eventCrossing) {
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| - | widget.modifyBackground(StateType.PRELIGHT, lightGray);
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| - | return false;
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| - | }
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| - | });
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| - | </source>
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| - | Here we react to the <b>EnterNotifyEvent</b>.
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| - | <source lang="java">
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| - | widget.modifyBackground(StateType.PRELIGHT, lightGray);
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| - | </source>
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| - | We modify the color of the button's background.
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| - | This chapter was about events in Java Gnome.
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| - | [[Категория:GTK+]]
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| - | [[Категория:Java]]
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