GUI Layout Managers and Components, Continue

1. GUI Layout Managers and Components, Continue • Card Layout • Borders • More GUI components • Menu • List • Sliders • Combo Boxes • Scroll Panes • Split Panes • Special Features of Swing components • Further GUI Programming Examples • Exercises Unit 13

2. Introduction • This is our concluding session on GUIs and event-driven programming. • In our discussion on GUI-based programs so far, we have covered: • GUI design issues, GUI components and containers. • Basic event handling. • Basic layout management. • We are going to cover: • More GUI components. • More layout managers. • Special Features of Swing components • With this coverage the student's knowledge base of the basics would be broadened. Unit 13

3. Card Layout Manager • A CardLayout object is a layout manager for a container. It treats each component in the container as a card. • Only one card is visible at a time, and the container acts as a stack of cards. • The first component added to a CardLayout object is the visible component when the container is first displayed. • The ordering of cards is determined by the container's own internal ordering of its component objects. • CardLayout defines a set of methods that allow an application to flip through these cards sequentially, or to show a specified card. • Card Layout has two constructors: • CardLayout(): Creates a new card layout with gaps of size zero. • CardLayout(int hgap, int vgap) Creates a new card layout with the specified horizontal and vertical gaps. Unit 13

4. Card Layout • Use the Card Layout class when you have an area that can contain different components at different times. • Panel cards = new Panel(); • CardLayout cardLayout = new CardLayout(); • cards.setLayout(cardLayout); • cards.add("Ace", new Button("Ace of Hearts")); • cards.add("Deuce", new Button("Two of Hearts")); • cards.add("Three", new Button("Three of Hearts")); Unit 13

5. Introduction to Borders • A border can be put around any Swing component to define how the edges of the component should be drawn. • The BorderFactory class is useful for creating border objects. • It has methods for creating specific types of borders. • A border is applied to a component using the setBorder method: JPanel myPanel = new JPanel(); Border myBorder = BorderFactory.createEtchedBorder(); myPanel.setBorder(myBorder); Unit 13

6. Borders • A line border • Surrounds the component with a simple line • The line's color and thickness can be specified • An etched border • Creates the effect of an etched groove around a component • Uses colors for the highlight and shadow • A bevel border • Can be raised or lowered • Uses colors for the outer and inner highlights and shadows Unit 13

7. Borders • A compound border • Is a combination of two borders • One or both of the borders can be a compound border • A titled border • Places a title on or around the border • The title can be oriented in many ways • A matte border • Specifies the sizes of the top, left, bottom, and right edges of the border separately • Uses either a solid color or an image. Unit 13

8. The BorderDemo Program Unit 13

9. MenuBar and Menu • A menu offers options to user. • Menus are not generally added to user interface. • Menu usually appears either in a menubar or as a popupmenu. • A JFrame often has a menu bar containing many menus; and each menu can contain many choices. • Menu bar can be added to a JFrame with the method setJMenuBar. JFrame window = new JFrame("Some Application"); JMenuBar menuBar = new JMenuBar(); window.setJMenuBar(menuBar); Unit 13

10. Menu • Menus are JMenu instances and added to menu bar: JMenu batter = new JMenu("Batter"); menuBar.add(batter); • Menu choices are JMenuIteminstances, and are added to menu: JMenuItem swing = new JMenuItem("Swing"); JMenuItem take = new JMenuItem("Take"); JMenuItem bunt = new JMenuItem("Bunt"); batter.add(swing); batter.add(take); batter.add(bunt); Unit 13

11. Lists • The Swing Jlist class represents a list of items from which the user can choose. • The contents of a JList object can be specified using an array of objects. • A JList object generates a list selection event when the current selection changes. • A JList object can be set so that multiple items can be selected at the same time. It can be one of three options: • Single selection – only one item can be selected at a time. • Single interval selection – multiple, contiguous items can be selected at a time. • Multiple interval selection – any combination of items can be selected. • The list selection mode is defined by a ListSelectionModel object. Unit 13

12. Declaring a JList String[] items = {“A", “B", “C", "D"}; JList list = new JList(items); list.setSelectionMode(DefaultListSelectionModel.SINGLE_SELECTION); // Set the item width int cellWidth = 200; list.setFixedCellWidth(cellWidth); // Set the item height int cellHeight = 18; list.setFixedCellHeight(cellHeight); // Get number of items in the list int size = list.getModel().getSize(); Unit 13

13. List Example Frame frame = new Frame(); frame.setLayout(new FlowLayout()); Button button1 = new Button("Next"); frame.add(button1); TextField text1 = new TextField(); text1.setColumns(10); frame.add(text1); Label label1 = new Label("First Name:"); frame.add(label1); TextArea textArea1 = new TextArea("This is some text in a text area"); textArea1.setRows(2); textArea1.setColumns(10); frame.add(textArea1); List list1 = new List(); list1.add("FirstItem"); list1.add("SecondItem"); list1.add("ThirdItem"); list1.add("FourthItem"); list1.add("FifthItem"); frame.add(list1); frame.pack(); frame.setVisible(true); Unit 13

14. Sliders • A slider is a component that allows the user to specify a numeric value within a bounded range. • The JSlider class has several methods that allow the programmer to tailor the look of a slider. • Major and minor tick marks, and labels on the tick marks, can be explicitly set and displayed. • A slider produces a change event. Unit 13

15. Sliders Declaration // Create a horizontal slider with min=0, max=100, value=50 JSlider slider = new JSlider(); // Create a horizontal slider with custom min and max; value is set to the middle int minimum = -255; int maximum = 256; slider = new JSlider(minimum, maximum); // Create a horizontal slider with custom min, max, and value int initValue = 0; slider = new JSlider(minimum, maximum, initValue); // Create a vertical slider with min=0, max=100, value=50 slider = new JSlider(JSlider.VERTICAL); // Create a vertical slider with custom min, max, and value slider = new JSlider(JSlider.VERTICAL, minimum, maximum, initValue); Unit 13

16. Combo Boxes • A combo box provides a menu from which the user can choose one of several options. • The currently selected option is shown in the combo box. • Unlike a JList object, a combo box shows its options only when the user presses it using the mouse. • Options can be established using an array of strings or using the addItem method. • A combo box generates an action event when the user makes a selection from it. // Create a read-only combobox String[] items = {"item1", "item2"}; JComboBox readOnlyCB = new JComboBox(items); // Create an editable combobox items = new String[]{"item1", "item2"}; JComboBox editableCB = new JComboBox(items); editableCB.setEditable(true); Unit 13

17. Scroll Panes • A scroll pane is useful for images or information too large to fit in a reasonably-sized area. • A scroll pane offers a limited view of the component it contains. • It provides vertical and/or horizontal scroll bars that allow the user to scroll to other areas of the component. • No event listener is needed for a scroll pane. // Create a scrollable text area JTextArea textArea = new JTextArea(); JScrollPane scrollableTextArea = new JScrollPane(textArea); // Create a scrollable list JList list = new JList(); JScrollPane scrollableList = new JScrollPane(list); Unit 13

18. Top Component Right Component Left Component Bottom Component Split Panes • A split pane (JSplitPane) is a container that displays two components separated by a moveable divider bar • The two components can be displayed side by side, or one on top of the other. Moveable Divider Bar Unit 13

19. Split Panes • The orientation of the split pane is set using the HORIZONTAL_SPLIT or VERTICAL_SPLIT constants • The divider bar can be set so that it can be fully expanded with one click of the mouse. • The components can be continuously adjusted as the divider bar is moved, or wait until it stops moving. • Split panes can be nested // Create a left-right split pane JSplitPane hpane = new JSplitPane(JSplitPane.HORIZONTAL_SPLIT, leftComponent, rightComponent); // Create a top-bottom split pane JSplitPane vpane = new JSplitPane(JSplitPane.VERTICAL_SPLIT, topComponent, bottomComponent); Unit 13

20. Special Features • Swing components offer special features to facilitate and enhance their use Unit 13

21. Tool Tips • Tool tips provide a short pop-up description when the mouse cursor rests momentarily on a component • A tool tip is assigned using the setToolTipText method of a Swing component. JButton button = new JButton ("Compute"); button.setToolTipText ("Calculate size."); Unit 13

22. Disabled Components • Components can be disabled if they should not be used. • A disabled component is "grayed out" and will not respond to user interaction. • The status is set using the setEnabled method: JButton button = new JButton (“Do It”); button.setEnabled (false); Unit 13