an introduction to java swing - comscigate.com filean introduction to java swing • what is java...

T A K E I T T O T H E N T H

An Introduction to Java Swing

Asif Habibullah

Member of Technical Staff, Software

Market Development Engineering

In Introduction to Java Swing


An Introduction to Java Swing• What is Java Swing?

• Swing GUI Fundamentals

• Swing Components

• Event Handling

• Model-View-Controller (MVC) Design Pattern

• Rich clients for Web Services

• Deploy via Java Web Start

What is Java Swing?

• Graphical User Interface (GUI) component toolkit.

• Complete set of user-interface elements written entirely in Java.

• Integrated into the Java 2 platform (1.2 or higher).

• No need to download and install on Java 2 platform.

• If running Java 1.1, you can download and install separately.

• Part of Java Foundation Classes (JFC)

Java Foundation Classes (JFC)� The Java Foundation Classes (JFC) extend the original Abstract

Window Toolkit (AWT) by adding a comprehensive set of graphical user interface class libraries

• What makes up the JFC (features)?

• Swing

• Accessibility API

• Java 2D API

• Drag and Drop API

• AWT

• Internationalization

What about AWT?

Swing AWT• Lightweight components

• Complex components

• Pluggable Look and Feel

• Pure Java – Platformindependent

• Heavyweight components

• Primitive components

• Single Look and Feel

• Not Pure Java – Platform dependent

Lightweight vs. Heavyweight

Lightweight Heavyweight• Not dependent on native peers

• Rely on primitive Java drawingtechniques in rendering.

• Components behavior is thesame across platforms.

• Look and Feel is independentof platform

• Dependent on native peers

• Rely on native windowingsystem in rendering.

• Component behavior maydiffer across platforms.

• Look and feel is dependenton platform

Swing GUI Fundamentals

• Swing components • Containers• Non-containers

• Layout Mangers

• Event Handling �

�

Swing Containers

� Used to hold other Swing containers and components.

� Two main types of containers:

– 1) Top level containers: � Root of the containment heirarchy� e.g. JFrame, JDialog, JApplet

– 2) Intermediate containers: � Middle nodes of containment heirarchy� e.g. JPanel, JScrollPane, JSplitPane, ...

� GUIs are usually made up of nested containers.

Swing Non-containers

� All of the other GUI elements that are not used to hold orpositions other GUI elements.

� 2 categories of non-containers:

� JButton� JComboBox� JTextField� JTable...

� JLabel� JToolTip� JProgressBar...

User input Data display/organization

Example: Swing Components

JButton

JComboBox

JTable

JFrame

JScrollPane

JTabbedPane

JMenuBar

JLabel

Layout Managers� Used by containers to position and organize their

components.

� Common Layout Managers:

– FlowLayout

– BorderLayout

– BoxLayout

– CardLayout

– GridLayout

– GridBagLayout

� Set container's layout by calling : Container.setLayout(LayoutManager manager)

FlowLayout

� FlowLayout lays out components left to right creating new rows as necessary.

� Default for JPanel.� Container.add(Component comp)

Source: http://java.sun.com/docs/books/tutorial/uiswing/layout/using.html

BorderLayout

� BorderLayout can hold components in the 5 areas: north, south, east, west, center.

� Default for JFrame.� Container.add(Component comp, int index)

// e.g. - index = BorderLayout.NORTH


BoxLayout

� BoxLayout simply positions components in a rows or columns.

� Example:


CardLayout

� A card layout is used when one wants to display different components at different times. A controller such as a JComboBox is normally used to flip through the different cards.

� Example:


GridLayout

� GridLayout will make all components the same size by placing them in a grid of specified row and column count.

� Example:


GridBagLayout

� Places components in a grid of rows and columns allowing specificed components to span mulitple rows and/or columns.

� Most flexible and robust of all layout managers.

� Example:


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Event Handling� The way a program handles user interactions with the

GUI

� Type of events:

– Mouse clicks

– Keyboard events

�

� Whenever an event occurs, all listeners that subscribe to that event are notified.

� For an object to be able to subscribe to an event, it just needs to implement the appropriate listener interface.

Event Source EventObject Event Listener

Event Handling (cont.)

� 2 key pieces of code:

1) Create the Listener class that implements the correct methods

2) Register the Listener with the component

� Easiest implementation: Use an Anonymous class

– Example:� JButton jb = new JButton();jb.addActionListener(new ActionListener(){

public void actionPerformed(Event e){System.err.println("Button clicked");

}});

Multiple Listeners

� Possible to register multiple listeners to a single component.

JButton ActionListener

MouseListener

FocusListener

Detect button click

Detect mouse over

Detect focus gain

The Event Thread

� When an event is dispatched, the code that is executed runs in the Event Thread.

� Code that runs in the event thread should execute very quickly.

� Time-consuming tasks:

– Loading of a file

– Running a benchmark

� These tasks should be run in their own thread.

SwingWorker Class� SwingWorker is a class that should be used to perform

time consuming tasks not to be run in the event thread.

Button Down

Load

Button Up

Button Down

Load

Button Up

Without SwingWorker With SwingWorker

SwingWorker - How to use it� In the Event Handling code:

– Create a class that extends SwingWorker.

– Override the public Object SwingWorker.construct() method with the time-consuming code (Loading, etc.)

– Override the public void SwingWorker.finished() method to execute code that MUST be executed after the completion of the SwingWorker Thread.

– Call SwingWorker.start()

� SwingWorker.finished() is run in the Event Thread after the SwingWorker thread is complete.

� Visit for details: http://java.sun.com/docs/books/tutorial/uiswing/misc/threads.html

Model-View-Controller(MVC) Design Pattern

� Model – An internal representation of the data displayed by the view.

� View – The interface that the user manipulates.

� Controller – Used to change state when the view is changed by the user.

View

Model

ControllerUser Interaction

Invoke State ChangeInvoke View Change

MVC - A Simple Example� SpreadSheet Application

– Model = TableModel

– View = JTable

– Controller = CellEditorListener

JTable

TableModel

CellEditorListenerUser Interaction

Invoke State ChangeInvoke View Change

Rich Clients for Web Services

� Talk given last year at Java One (2001) by Howard Rosen, Hans Muller, Scott Violet of the Java Client Group

� Details can be found at: http://java.sun.com/products/jfc/tsc/articles/javaOne2001/2734/index.html

� Summary: Rich Clients + Web Services = Best Web Experience

� Web Services

– Not only for browser based applications.

– Create rich clients using Java Technologies.

– Deploy Java applications via Java Web Start

Java [tm] Technology Web Services Model

Why Build Rich Clients?

� Dynamic, Responsive, Easy to use

� Competitive edge, not just HTML

� Real-time visualization

� Decouple server performance from GUI

� Support offline usage

Client - Server Communication

� Speak HTTP just like your browser-based applications.

� Server-side code does not need to change.

� Low bandwidth connection to the server

� 1 second round trips typical

– If > 1 second; use a worker thread to communicate.� Just like SwingWorker

– Always keep GUI reponsive

Deploying via Java Web Start� Single click deployment:

– User clicks on a link in a browser

– Application starts

� Eliminates the install step

� Based on JSR-56: Java Network Launching Protocol and API

� Downloaded application runs outside of the browser, unlike an applet.

� Guaranteed to run the most current version of the application.

Summary

� Java Swing provides developers to create complex 100% Java based GUIs.

� A whole lot more out there that we did not talk about:

– Pluggable Look and Feel

– Drag and Drop

– Internationalization ...

� The Java Tutorial

– http://java.sun.com/docs/books/tutorial/


Asif Habibullah

[email protected]

an introduction to java swing - comscigate.com filean introduction to java swing • what is java...

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