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

15-8 Copyright © 2005, Oracle. All rights reserved. 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

15-10 Copyright © 2005, Oracle. All rights reserved. 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)); }

15-12 Copyright © 2005, Oracle. All rights reserved. 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.

15-13 Copyright © 2005, Oracle. All rights reserved. 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. Click menu bar object in Structure pane to display menu bar Context menu when right-clicking a menu item

15-14 Copyright © 2005, Oracle. All rights reserved. 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

15-20 Copyright © 2005, Oracle. All rights reserved. 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.

15-21 Copyright © 2005, Oracle. All rights reserved. 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());

15-22 Copyright © 2005, Oracle. All rights reserved. OK Source Event listener object Handler method Event Handling Process: Registration MyListener actionListenerObj = new MyListener(); public void jbInit() { button1.addActionListener(actionListenerObj); … }

15-24 Copyright © 2005, Oracle. All rights reserved. Event Handling Process: The Event Occurs Notified public void jbInit() { button1.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent e) { // Your code to handle the ActionEvent } }); … } OK Source Event listener object Handler method

15-26 Copyright © 2005, Oracle. All rights reserved. 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.

15-27 Copyright © 2005, Oracle. All rights reserved. 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 View Event modify Notify update Get changed data

15-30 Copyright © 2005, Oracle. All rights reserved. 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 components capabilities.

15-31 Copyright © 2005, Oracle. All rights reserved. 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

15-33 Copyright © 2005, Oracle. All rights reserved. 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 Handler in JDeveloper

15-34 Copyright © 2005, Oracle. All rights reserved. public void jbInit() throws Exception { … findButton.addActionListener( new java.awt.event.ActionListener() { public void actionPerformed(ActionEvent e) { findButton_actionPerformed(e); } }); … void findButton_actionPerformed(ActionEvent e) { // Your code to handle the ActionEvent } Find Default Event Handling Code Style Generated by JDeveloper

15-35 Copyright © 2005, Oracle. All rights reserved. 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

15-36 Copyright © 2005, Oracle. All rights reserved. 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

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

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

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