12slide_2007 - Chapter 12 GUI Basics EE3206/EE5805 Java...

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Unformatted text preview: Chapter 12 GUI Basics EE3206/EE5805 Java Programming & Applications 1 Objectives To distinguish simple GUI components. To To describe the Java GUI API hierarchy. To To create user interfaces using frames, panels, and simple UI components. To To understand the role of layout managers. To To use the FlowLayout, GridLayout, and BorderLayout managers to layout To components in a container. To specify colors and fonts using the Color and Font classes. To To use JPanel as subcontainers. To EE3206/EE5805 Java Programming & Applications 2 Creating GUI Objects // Create a button with text OK JButton jbtOK = new JButton("OK"); JButton("OK"); // Create a label with text "Enter your name: " JLabel jlblName = new JLabel("Enter your name: "); // Create a text field with text "Type Name Here" JTextField jtfName = new JTextField("Type Name Here"); // Create a check box with text bold JCheckBox jchkBold = new JCheckBox("Bold"); JCheckBox("Bold"); // Create a radio button with text red JRadioButton jrbRed = new JRadioButton("Red"); JRadioButton("Red"); // Create a combo box with choices red, green, and blue JComboBox jcboColor = new JComboBox(new String{"Red", "Green", "Blue"}); Label Text field Check Box Radio Button Combo Box Button EE3206/EE5805 Java Programming & Applications 3 Swing vs. AWT So why do the GUI component classes have a prefix J? Instead of JButton, why not name it simply Button? In fact, there is a class already named Button in the java.awt package. When Java was introduced, the GUI classes were bundled in a library known as the Abstract Windows Toolkit (AWT). For every platform on which Java runs, the AWT components are automatically mapped to the platform-specific components through their respective agents, known as peers. AWT is fine for developing simple graphical user interfaces, but not for peers developing comprehensive GUI projects. Besides, AWT is prone to platform-specific bugs because its peer-based approach relies heavily on the underlying platform. With the release of Java 2, the AWT user-interface components were replaced by a more robust, versatile, and flexible library known as Swing components. Swing components are painted Swing directly on canvases using Java code, except for components that are subclasses of java.awt.Window or java.awt.Panel, which must be drawn using native GUI on a specific platform. Swing components are less dependent on the target platform and use less of the native GUI resource. For this reason, Swing components that don’t rely on native GUI are referred to as lightweight components, and AWT components are referred to as heavyweight lightweight heavyweight components. EE3206/EE5805 Java Programming & Applications 4 GUI Class Hierarchy (Swing) Dimension Font FontMetrics Object Color Graphics Component * LayoutManager 1 Classes in the java.awt package Heavyweight Panel Applet JApplet Container Window Frame Dialog JFrame JDialog JComponent Swing Components in the javax.swing package Lightweight EE3206/EE5805 Java Programming & Applications 5 GUI Container Classes Dimension Font FontMetrics Object Color Graphics Component * LayoutManager 1 Classes in the java.awt package Heavyweight Panel Applet JApplet Container Window Frame Dialog JFrame JDialog JComponent JPanel Container classes can contain other GUI components. Lightweight Swing Components in the javax.swing package EE3206/EE5805 Java Programming & Applications 6 GUI Helper Classes Dimension Font FontMetrics Object Color Graphics Component * LayoutManager 1 Classes in the java.awt package Heavyweight Panel Applet JApplet Container Window Frame Dialog JFrame JDialog JComponent JPanel The helper classes are not subclasses of Component. They are used to describe the properties of GUI components such as graphics context, colors, fonts, and dimension. Swing Components in the javax.swing package Lightweight EE3206/EE5805 Java Programming & Applications 7 Swing GUI Components JCheckBoxMenuItem JMenuItem JMenu JRadioButtonMenuItem JCheckBox JRadioButton AbstractButton JButton JToggleButton JComponent JTextComponent JEditorPane JTextField JTextArea JPasswordField JLabel JList JComboBox JSplitPane JPanel JOptionPane JSeparator JFileChooser JScrollBar JScrollPane JColorChooser JSlider JRootPane JToolTip JTabbedPane JToolBar JTree JLayeredPane JPopupMenu JMenuBar JTable JTableHeader JInternalFrame JProgressBar JSpinner EE3206/EE5805 Java Programming & Applications 8 AWT (Optional) AWTEvent Font FontMetrics Object Color Graphics Component Container Button Label TextComponent Panel Window Applet Frame Dialog FileDialog TextField List Choice CheckBox TextArea LayoutManager CheckBoxGroup Canvas MenuComponent MenuItem MenuBar Menu Scrollbar EE3206/EE5805 Java Programming & Applications 9 Frames and JFrame Class Frame is a window that is not contained inside another window. Frame Frame is the basis to contain other user interface components in Java GUI applications. For Swing GUI programs, use JFrame class to create widows. For javax.swing.JFrame +JFrame() +JFrame(title: String) +getSize(width: int, height: int): void +setLocation(x: int, y: int): void +setVisible(visible: boolean): void +setDefaultCloseOperation(mode: int): void +setLocationRelativeTo (c: Component): void Creates a default frame with no title. Creates a frame with the specified title. Specifies the size of the frame. Specifies the upper-left corner location of the frame. Sets true to display the frame. Specifies the operation when the frame is closed. Sets the location of the frame relative to the specified component. If the component is null, the frame is centered on the screen. EE3206/EE5805 Java Programming & Applications 10 Creating Frames import javax.swing.*; public class MyFrame { public static void main(String args) { JFrame frame = new JFrame("Test Frame"); frame.setSize(400, 300); frame.setVisible(true); frame.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE); } } MyFrame Run EE3206/EE5805 Java Programming & Applications 11 Adding Components into a Frame // Add a button into the frame frame.getContentPane().add(new JButton("OK")); Title bar Content pane MyFrameWithComponents Run EE3206/EE5805 Java Programming & Applications 12 Content Pane Delegation in JDK 1.5 // Add a button into the frame frame.getContentPane().add(new JButton("OK")); Title bar // Add a button into the frame frame.add(new JButton("OK")); Content pane MyFrameWithComponents EE3206/EE5805 Java Programming & Applications Run 13 Layout Managers Java’s layout managers provide a level of abstraction to Java automatically map your user interface on all window systems. The UI components are placed in containers. Each container has a The layout manager to arrange the UI components within the container. Layout managers are set in containers using the Layout setLayout(LayoutManager) method in a container. Kinds of Layout Manager Kinds FlowLayout FlowLayout GridLayout GridLayout BorderLayout BorderLayout EE3206/EE5805 Java Programming & Applications 14 FlowLayout Example Write a program that adds three labels and text fields into the content pane of a frame with a FlowLayout manager. ShowFlowLayout Run EE3206/EE5805 Java Programming & Applications 15 The FlowLayout Class java.awt.FlowLayout -alignment: int -hgap: int -vgap: int +FlowLayout() +FlowLayout(alignment: int) +FlowLayout(alignment: int, hgap: int, vgap: int) The get and set methods for these data fields are provided in the class, but omitted in the UML diagram for brevity. The alignment of this layout manager (default: CENTER). The horizontal gap of this layout manager (default: 5 pixels). The vertical gap of this layout manager (default: 5 pixels). Creates a default FlowLayout manager. Creates a FlowLayout manager with a specified alignment. Creates a FlowLayout manager with a specified alignment, horizontal gap, and vertical gap. EE3206/EE5805 Java Programming & Applications 16 GridLayout Example Rewrite the program in the preceding example using a GridLayout manager instead of a FlowLayout manager to display the labels and text fields. ShowGridLayout Run EE3206/EE5805 Java Programming & Applications 17 The GridLayout Class java.awt.GridLayout -rows: int -columns: int -hgap: int -vgap: int +GridLayout() The get and set methods for these data fields are provided in the class, but omitted in the UML diagram for brevity. The number of rows in this layout manager (default: 1). The number of columns in this layout manager (default: 1). The horizontal gap of this layout manager (default: 0). The vertical gap of this layout manager (default: 0). Creates a default GridLayout manager. +GridLayout(rows: int, columns: int) Creates a GridLayout with a specified number of rows and columns. +GridLayout(rows: int, columns: int, Creates a GridLayout manager with a specified number of rows and hgap: int, vgap: int) columns, horizontal gap, and vertical gap. EE3206/EE5805 Java Programming & Applications 18 The BorderLayout Manager BorderLayout The BorderLayout manager divides the container into five areas: BorderLayout East, South, West, North, and Center. Components are added to a BorderLayout by using the add method. BorderLayout add(Component, constraint); where constraint is constraint BorderLayout.EAST, BorderLayout.EAST BorderLayout.SOUTH, BorderLayout.SOUTH BorderLayout.WEST, BorderLayout.WEST BorderLayout.NORTH, or BorderLayout.NORTH BorderLayout.CENTER. BorderLayout.CENTER EE3206/EE5805 Java Programming & Applications 19 BorderLayout Example ShowBorderLayout Run 20 EE3206/EE5805 Java Programming & Applications The BorderLayout Class BorderLayout The get and set methods for these data fields are provided in the class, but omitted in the UML diagram for brevity. The horizontal gap of this layout manager (default: 0). The vertical gap of this layout manager (default: 0). Creates a default BorderLayout manager. java.awt.BorderLayout -hgap: int -vgap: int +BorderLayout() +BorderLayout(hgap: int, vgap: int) Creates a BorderLayout manager with a specified number of horizontal gap, and vertical gap. EE3206/EE5805 Java Programming & Applications 21 The Color Class Color You can set colors for GUI components by using the java.awt.Color class. Colors are made of red, green, and blue components, each of which is represented by a byte value that describes its intensity, ranging from 0 (darkest shade) to 255 (lightest shade). This is known as the RGB model. RGB Color c = new Color(r, g, b); r, g, and b specify a color by its red, green, and blue components. Example: Color c = new Color(228, 100, 255); EE3206/EE5805 Java Programming & Applications 22 Standard Colors Thirteen standard colors (black, blue, cyan, darkGray, gray, green, lightGray, magenta, orange, pink, red, white, yellow) are defined as constants in java.awt.Color. The standard color names are constants, but they are named as variables with lowercase for the first word and uppercase for the first letters of subsequent words. Thus the color names violate the Java naming convention. Since JDK 1.4, you can also use the new constants: BLACK, BLUE, CYAN, DARK_GRAY, GRAY, GREEN, LIGHT_GRAY, MAGENTA, ORANGE, PINK, RED, WHITE, and YELLOW. EE3206/EE5805 Java Programming & Applications 23 Setting Colors You can use the following methods to set the component’s background and foreground colors: setBackground(Color c) setForeground(Color c) Example: jbt.setBackground(Color.yellow); jbt.setBackground(Color.YELLOW); jbt.setForeground(Color.lightGray); jbt.setBackground(Color.LIGHT_GRAY); EE3206/EE5805 Java Programming & Applications 24 The Font Class Font Font Names Standard font names that are supported in all platforms are: SansSerif, Serif, Monospaced, Dialog, or DialogInput. Font Style Font.PLAIN (0), Font.BOLD (1), Font.ITALIC (2), and Font.BOLD + Font.ITALIC (3) Font myFont = new Font(name, style, size); Example: Font myFont = new Font("SansSerif ", Font.BOLD, 16); Font myFont = new Font("Serif", Font.BOLD+Font.ITALIC, 12); JButton jbtOK = new JButton("OK“); jbtOK.setFont(myFont); EE3206/EE5805 Java Programming & Applications 25 Finding All Available Font Names To know what fonts are available in the system To environment, you may run the following code: GraphicsEnvironment e = GraphicsEnvironment.getLocalGraphicsEnvironment(); String fontnames = e.getAvailableFontFamilyNames(); for (int i = 0; i < fontnames.length; i++) System.out.println(fontnames[i]); EE3206/EE5805 Java Programming & Applications 26 Using Panels as Sub-Containers Panels act as sub-containers for grouping user interface Panels components. It is recommended that you place the user interface components in It panels and place the panels in a frame. You can also place panels in a panel. Decompose into manageable sub-interface Decompose Easy for management Easy To add a component to JFrame, you actually add it to the content To pane of JFrame. To add a component to a panel, you add it directly to the panel using the add method. EE3206/EE5805 Java Programming & Applications 27 Creating a JPanel You can use new JPanel() to create a panel with a default FlowLayout manager or new JPanel(LayoutManager) to create a panel with the specified layout manager. Use the add(Component) method to add a component to the panel. For example, JPanel p = new JPanel(); p.add(new JButton("OK")); EE3206/EE5805 Java Programming & Applications 28 Testing Panels Example This example uses panels to organize components. The program creates a user interface for a Microwave oven. frame A textfield p2 A button 12 buttons p1 TestPanels Run EE3206/EE5805 Java Programming & Applications 29 Common Features of Swing Components java.awt.Component -font: java.awt.Font -background: java.awt.Color -foreground: java.awt.Color -preferredSize: Dimension -visible: boolean +getWidth(): int +getHeight(): int +getX(): int +getY(): int The get and set methods for these data fields are provided in the class, but omitted in the UML diagram for brevity. The font of this component. The background color of this component. The foreground color of this component. The preferred size of this component. Indicates whether this component is visible. Returns the width of this component. Returns the height of this component. getX() and getY() return the coordinate of the component’s upper-left corner within its parent component. java.awt.Container +add(comp: Component): Component Adds a component to the container. +add(comp: Component, index: int): Component Adds a component to the container with the specified index. Removes the component from the container. +remove(comp: Component): void +getLayout(): LayoutManager +setLayout(l: LayoutManager): void +paintComponents(g: Graphics): void Returns the layout manager for this container. Sets the layout manager for this container. Paints each of the components in this container. The get and set methods for these data fields are provided in the class, but omitted in the UML diagram for brevity. javax.swing.JComponent The tool tip text for this component. Tool tip text is displayed when the mouse points on the component without clicking. EE3206/EE5805 Java Programming & Applications The border for this component. -border: javax.swing.border.Border -toolTipText: String 30 Borders You can set a border on any object of the JComponent class. Swing has several types of borders. To create a titled border, use new TitledBorder(String title); new To create a line border, use new LineBorder(Color color, int width); new where width specifies the thickness of the line. For example, the following code displays a titled border on a panel: JPanel panel = new JPanel(); panel.setBorder(new TitleBorder(“My Panel”)); EE3206/EE5805 Java Programming & Applications 31 Test Swing Common Features Component Properties JComponent Properties font font background background foreground foreground preferredSize preferredSize minimumSize minimumSize maximumSize maximumSize toolTipText toolTipText border border TestSwingCommonFeatures EE3206/EE5805 Java Programming & Applications Run 32 Image Icons Java uses the javax.swing.ImageIcon class to represent an icon. An icon is a fixed-size picture; typically it is small and used to decorate components. Images are normally stored in image files. You can use new ImageIcon(filename) to construct an image icon. For example, the following statement creates an icon from an image file us.gif in the image directory under the current class path: ImageIcon icon = new ImageIcon("image/us.gif"); TestImageIcon EE3206/EE5805 Java Programming & Applications Run 33 ...
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This note was uploaded on 01/11/2011 for the course EE 3206 taught by Professor Cwting during the Spring '07 term at City University of Hong Kong.

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