September 29, 2009 CS 350 Lecture 10 1CS 350: Computer/Human InteractionLecture 10 Overview●Java basics●Java Swing applications●Input elements and listeners●Message dialogs, menus●File output●Java Swing applets●References: JTUT, JSWI, JAPISeptember 29, 2009 CS 350 Lecture 10 2CS 350: Computer/Human InteractionJava Basics●Everything is part of a class, including static methods●Application is a class with a static main method●Class can extend another class; i.e., inherits superclass data and methods●Class can implement an interface; i.e., “inherits” and must implement the methods of the interfaceSeptember 29, 2009 CS 350 Lecture 10 3CS 350: Computer/Human InteractionJava Basics●All objects are dynamically createdJLabel title = new JLabel ("A label");●Console output using System.outSystem.out.print ("Output without newline");System.out.println ("Output with newline");●String concatenation operator is +, all objects convert using toString methodtitle.setText ("A new label: " + number);September 29, 2009 CS 350 Lecture 10 4CS 350: Computer/Human InteractionIn-class Exercise 1●Download PizzaJava1-3.zip from course website.●File unzips into a Java Eclipse workspace with 5 projects●Launch Eclipse, File → Switch Workspace, browse to the workspace folder●Look at HelloWorldApp.javaSeptember 29, 2009 CS 350 Lecture 10 5CS 350: Computer/Human InteractionJava Swing●Sun Swing Tutorial (JSWI) is very good or follow links on API (JAPI) pages●Swing is a GUI toolkit of components implemented in Java on top of AWT (Abstract Windowing Toolkit). Components are nested.●Every GUI must have a base top-level component, most commonly: JFrame or JAppletSeptember 29, 2009 CS 350 Lecture 10 6CS 350: Computer/Human InteractionJava Swing●Top-level containers consist of a JRootPane, the area under the title bar, with a JLayeredPane child that manages the menu bar, if there is one, with a Container child, called the content pane, where GUI components are managed.●Characteristics of the environment can be obtained from the singleton Toolkit object.●Look at Pizza1App.javaSeptember 29, 2009 CS 350 Lecture 10 7CS 350: Computer/Human InteractionJava Applications●A Java application class extends a JFrame or has a JFrame data member; constructor creates GUI.●Swing is not thread-safe, so use SwingUtilities.invokeLater() with new anonymous inner class that implements Runnable interface to create application.●The event-dispatcher will execute the code in the run method in a separate thread.September 29, 2009 CS 350 Lecture 10 8CS 350: Computer/Human InteractionGUI Components●JLabel – label with text●JTextField – one line of text●JTextArea – multiple lines of text●JRadioButton – radio button, grouped using ButtonGroup●JCheckBox – check boxes●JButton – button with text labelSeptember 29, 2009 CS 350 Lecture 10 9CS 350: Computer/Human InteractionGUI Components●JPanel – container with layout, used to position components●Text can include HTML tags●Most components allow their border to be set; BorderFactory class contains methods for creating various border optionsSeptember 29, 2009 CS 350 Lecture 10 10CS 350: Computer/Human InteractionJava Events●GUI interaction is event-driven similar to VB●Event-dispatching thread is automatically created●Events include: clicks, keypress, mouse move, etc.●Event-handling interfaces defined by AWTSeptember 29, 2009 CS 350 Lecture 10 11CS 350: Computer/Human InteractionListeners●Interaction is provided by adding a listener to a component●Listeners are interfaces with methods that must be implemented. E.g., ActionListener interface has actionPerformed; ItemListener interface has itemStateChanged●Often use an anonymous inner class to implement these interfaces.September 29, 2009 CS 350 Lecture 10 12CS 350: Computer/Human InteractionLayout Managers●Layout manager determines where components appear in a panel; each panel can have a different layout manager●FlowLayout: default panel manager; left to right placement●BorderLayout: default root pane manager; north, south, west, east, and center placementsSeptember 29, 2009 CS 350 Lecture 10 13CS 350: Computer/Human InteractionLayout Managers●GridLayout: equal-sized cells of specified number of rows and columns (0 is undetermined); left to right, top to bottom default placement ●BoxLayout: centered placement, either horizontally or vertically●SpringLayout: most general, placement determined by spring constraints between componentsSeptember 29, 2009 CS 350 Lecture 10 14CS 350: Computer/Human InteractionMore GUI Components●Look at Pizza2App.java●JComboBox – construct with array of string items–Uses ActionListener interface, dynamically cast the source of the event object into a JComboBox and get the selected itemSeptember 29, 2009 CS 350 Lecture 10 15CS 350: Computer/Human InteractionMore GUI Components●JList – construct with array of string items–Uses ListSelectionListener interface with valueChanged function–MULTIPLE_INTERVAL_SELECTION mode is default, also SINGLE_SELECTION and SINGLE_INTERVAL_SELECTION modes–getSelectedIndices method returns int array of indices of selected itemsSeptember 29, 2009 CS 350 Lecture 10 16CS 350: Computer/Human InteractionMessage Dialogs●Simple OK message dialogs can be created usingJOptionPane.showMessageDialog()●Arguments are the top-level frame, dialog message, window title, and message type (determines the icon); can also add icon image argumentSeptember 29, 2009 CS 350 Lecture 10 17CS 350: Computer/Human InteractionMenu Bars and Menus●JMenuBar is added to top-level layered pane: setJMenuBar(createMenuBar());●Default placement is platform-dependent●Add JMenu objects to menu bar●Add JMenuItem, JMenu objects to menus●Uses ActionListener interfaceSeptember 29, 2009 CS 350 Lecture 10 18CS 350: Computer/Human InteractionFile Output●General paradigm is to wrap a buffered stream around an unbuffered stream around a file.●Using a file must be in try-catch blockPrintWriter outputStream = null;try { outputStream = new PrintWriter( new FileWriter ("output/orders.txt")); outputStream.println (...);} catch (IOException ex) { // error code} finally { // clean up code }September 29, 2009 CS 350 Lecture 10 19CS 350: Computer/Human InteractionMiscellaneous●Added keyboard mnemonics to buttonssubmit.setMnemonic (KeyEvent.VK_S);Underlines the letter in the labelSeptember