15 Copyright © 2005, Oracle. All rights reserved. Adding User Interface Components and Event Handling.

15Copyright © 2005, Oracle. All rights reserved.

Adding User Interface Componentsand Event Handling

15-2 Copyright © 2005, Oracle. All rights reserved.

Objectives

After completing this lesson, you should be able to do the following:

• Add Swing components to an application

• Get and modify the contents of the components

• Provide event handlers for common types of events

• Create a menu bar


Swing Components

• Text controls– JTextField– JPasswordField– JTextArea– JEditorPane– JTextPane

• Graphic controls– JTree– JTable– JToggleButton


Swing Components in JDeveloper

Use the Swing Component Palette to add items.


System Navigator

Invoking the UI Editor

Right-click and select Open from the Context menu.

Code Editor

Context menu


1: Open the Component Palette; select the Swing category.

2: Drag the component to the form. The class updates automatically.

How to Add a Component to a Form


Change property values in the Inspector.

Edit the Properties of a Component


Code Generated by JDeveloper

For example: Adding a JButton to a Jframe:

import javax.swing.JButton;

public class JFrame1 extends JFrame {

JButton jButton1 = new JButton();

...

public void jbInit() throws Exception {

...

jbutton1.setText("jButton1");

...

this.getContentPane().add(jButton1,

new XYConstraints(21, 20, 118, 48));

}


Creating a Menu

• Select “Create Menu Bar” during application creation.

• Add a JMenuBar from the Component Palette.• JDeveloper creates:

– JMenuBar for visual container for menus– JMenu, which represents a menu of items, added to

a menu bar– JMenuItems, which are placed in a JMenu

• Each JMenuItem supports events, interfaces, and handler methods in the same way as with other Swing UI components.

• A JMenuBar can be added to any top-level container, such as Frames, Dialogs, or Applets.


Using JDeveloper Menu Editor

• In the JDeveloper Menu Editor, use the Structure pane:– Expand the Menu node.– Click the menu bar object for a visual

representation.– Right-click menu or menu items to alter

structure from the Context menu options.

Clickmenu barobject in

Structure paneto displaymenu bar

Context menu when

right-clicking a menu item


Practice 15-1: Overview

This practice covers:

• Creating the OrderEntryMDIFrame menu

• Adding the menu items and a separator to the Order menu

• Adding components to OrderEntryFrame to form its visual structure


UI for Java Application


Java Event Handling Model

• How it works:– Event originates from source and generates an

event object.– An event listener hears a specific event.– An event handler determines what to do.

• Setting it up:1. Create an event source object.

2. Create an event listener object implementing an interface with methods to handle the event object.

3. Write an event-specific method to handle the event.

4. Register the listener object with the event source for the specified event.


Event Handling Code Basics

• Create the event source.

• Create the event listener implementing the required event interface.

• Register the listener with the event source.

Jbutton findBtn = new Jbutton("Find");

class MyListener implements ActionListener {

public void actionPerformed(ActionEvent e) {

// handler logic

}

}

findBtn.addActionListener(new MyListener());


OK

SourceEvent listener object

Handler method

Event Handling Process: Registration

MyListener actionListenerObj = new MyListener();

public void jbInit() {

button1.addActionListener(actionListenerObj);

…

}


Event Handling Process:The Event Occurs

Notified

public void jbInit() {

button1.addActionListener(new ActionListener() {


// Your code to handle the ActionEvent

}

}); … }

OK


Handler method


Event Handling Process:Running the Event Handler

SourceOK


Handler method:save changes and quit


interface MouseListener {

// Declares five methods

} class MouseAdapter implements MouseListener {

// Empty implementations of all five methods

}

public class MyListener extends MouseAdapter {

// Override only the methods you need

}

Using Adapter Classes for Listeners

Adapter classes are “convenience” classes that implement event listener interface:• They provide empty method implementations.• They are extended and the desired method

overridden.


Swing Model View Controller Architecture

• Model, View, Controller principles

• Terms explained:– Model represents the data or information.– View provides a visual representation of the data.– Controller handles events modifying the

view/model.

• Always update Swing components on the event thread queue, or use SwingUtilities methods.

Model

Controller ViewViewEventmodify

modify Notify update

Get changed data


Basic Text Component Methods

• Text item (JLabel, JTextField, and JButton) methods:void setText(String value)

String getText()

• Additional methods in JTextArea:void append(String value)

void insert(String value, int pos)

• Changes to component contents are usually done in the event handling thread.

Note: Consult the Java API documentation for details about each component’s capabilities.


Basic JList Component Methods

Subset of JList component methods include:• void setListData(Vector)

– Copies Vector to a ListModel applied with setModel

• void setModel(ListModel)– Sets model representing the data and clears

selection. Uses DefaultListModel class for the model.

• Object getSelectedValue()– Returns the selected object, or null if nothing is

selected• int getSelectedIndex()

– Returns the index of the selected item, or –1 if nothing is selected


Events that a component can generate

Event handler methods

What Events Cana Component Generate?


1: Select the event that you want to handle.

2: Click the right column to fill in a method name.

3: Double-click the right column to create the method.

How to Define an Event Handlerin JDeveloper


public void jbInit() throws Exception {

…

findButton.addActionListener(

new java.awt.event.ActionListener() {


findButton_actionPerformed(e);

}

}); …

void findButton_actionPerformed(ActionEvent e) {

// Your code to handle the ActionEvent

}

Find

Default Event Handling Code Style Generated by JDeveloper


public class JFrame1 extends JFrame {

…

void findButton_actionPerformed(ActionEvent e){

// When the user clicks the button, display

// the list of customers in jTextArea1

String findList = (“Supplies-R-Us " + "\n" +

“Consulting Inc. " + "\n" +

“Just-In-Time Training ");

jTextArea1.setText(findList);

}

}

Completing the Event Handler Method


Summary

In this lesson, you should have learned how to:

• Add a Swing component to a visual container

• Get and modify the contents of the components

• Use the AWT event handling model to:– Create an event source– Create an event listener and handler code– Register an event listener for the event to be

handled

• Create a menu bar with menus and menu items

• Handle events


Practice 15-2: Overview

This practice covers adding event handling for:

• Order > New menu

• Find Customer button

• Add Product button

15 Copyright © 2005, Oracle. All rights reserved. Adding User Interface Components and Event Handling.

Documents

event object

menu bar slide

menu item slide

component slide

specific event

event source object

event handlers

specified event