Java Swing GUIs and Arrays Tutorial

CSSE221: Software Dev. Honors Day 8 • Announcements • HW3 due now, solutions will be posted. • Questions on Arrays? • Max # of elements in an array: • Integer.MAX_INT, but your machine probably doesn’t have enough space to hold this much data! And the JVM will certainly not claim all your memory even if you did. • Newer machines (with 64-bit addressing) will have more… but I don’t know how Java is responding (perhaps Java 7 will have long int array indices) • Today is Constitution Day. • Speaker in Kahn Room in Union, 10th hour. • No baby yet…

Capsule Deliverables: sec 1 • Please email the quiz, key, and summary to me by 7:30 am on the day you are presenting. • Send .doc files • (If you get them to me by 3pm on a weekday before you present, I’ll still print them) • Lessons from week 1: • Nice research and summarization! • Proofread your stuff. Everyone else will see it. • 1-page quizzes are good (or staple) • Summaries don’t have to be verbose, just dense with info.

This week: Fifteen assignment • Monday: • Fifteen specification • GUIs using Java’s Swing library • Intro to UML as a design tool • Start Fifteen • Tuesday: • EventListeners: responding to user input • Time to work on project • Thursday: • Anonymous classes (capsule) • Function objects and comparators (capsule)

“Fifteen” Arrays (especially 2D) Creating GUIs using Swing Responding to mouse clicks

Fifteem Teams Repos is csse221-200810-<usr1>-<usr2>. If solo, use your personal repos. • beltonj1-fishmad • bennetrn-leveyjr • bennindp-speyerea • crockeea-morrisps • devorejd-priestjs • lundgrpb-skilessa • johnsoad-smithny • sullivja-wentztj • mcginnda Discuss how to pair-program

The Java Swing Library • JFrames, JTextBoxes, JButtons, JScrollPanes… what’s available? • What components will I need… • …now, for Fifteen? • …later, for a term project? • Browse the Visual Index to the Swing Components in Sun’s Java Tutorial.

JFrame • A simple window that contains the other GUI components • Background Color • getContentPane().setBackground(Color); • Make sure to set visible • setVisible(true); • Setting the size • setSize(width, height);

Benefits of Extending JFrame or JComponents like JPanel • When extending the JFrame class we can still instantiate it as JFrame. • “Controlling” the JFrame is easier to comprehend when we do not need the calling object stated every time. i.e. setSize(w,h); instead of jFrameObject.setSize(w,h);

JLabel • Displays text to user • User cannot edit text • Construction: JLabel message = new JLabel(String text); Methods: • String text = message.getText(); • message.setText(String text);

JTextField • Lets user enter or modify a single line of text • Construction: • JTextField text = new JTextField(int WidthInCharacters); • Getting the Text: • String input = text.getText(); • Setting text in a Text Field: • text.setText(String output);

JTextArea • Lets user enter or modify multiple lines of text. • Declaration: private JTextArea text; • Constructors: • text = new JTextArea(int rows, int columns); • text = new JTextArea(String output); • text = new JTextArea(String output, int rows, int columns); • Useful methods: • String input = text.getText(); • text.setText(String output); • setEditable(Boolean editable); • boolean editable = text.isEditable();

JButton • Used to let user execute action • Construction: JButton button = new JButton(String text); • button.setBackground(Color color);

JPanel • Simple container that groups objects • Meant to subdivide • Creation Syntax: • JPanel panelName = new JPanel(); • Useful attributes and methods • .setLayout(new Layout()); • .add(component); • .setBackground(Color color);

Layout Managers • Frames are organized by layout managers. • Organizes the locations of the components within the frame • Not only frames use layout managers, but Panels are also organized by layout managers. • Allows for panels within panels.

Layout: Flow Layout • Places the components from the left side to the right side. • Wraps around the right side. • .setLayout(new FlowLayout()); • No special add syntax.

Layout: Border Layout • North, South, East, West, Center • setLayout(new BorderLayout()); • .add(component, BorderLayout.NORTH);

Layout: Grid Layout • Similar to flow in the left to right manner, but the grid that you define limits the size of any one component • You can leave out a definite definition of how many rows or columns are in the grid. • setLayout(new GridLayout(r,c)); • Adds in components from left to right, top to bottom. Cannot specify which block.

PaintComponent • Used with JPanels, and all JComponents, to paint the components on the screen. • Called automatically, no need to invoke it. • Use repaint(); to force the paintComponent() method to execute. • Start with super.paintComponent(g); where g is your Graphics object publicvoid paintComponent(Graphics g) { super.paintComponent(g); setBackgroundColor(Color.red); g.drawOval(10,40,20,20); }

Alternative designs • I want a component to appear. Question: • Should I paint it? Add a new component? • Answer: It depends… • On how much control you want over its appearance • On how you want it to respond to events • It’s usually a tradeoff. Press me!

Listeners • If you want to respond to events, you need to implement a Listener interface. • We’ll look at these in detail tomorrow

Demo together

Java Swing GUIs and Arrays Tutorial