Lesson 5 GUI Programming AUBG ICoSCIS Team Assoc. Prof. Stoyan Bonev March, 23 - 24, 2013 SWU, Blagoevgrad Lesson Contents: Building Win apps technologies using Java & class libraries Swing AWT (Abstract Windows Toolkit) 3 Java GUI programming Java GUI programming has its own specific: Terminology Concept Philosophy Ideology Technologies: • Hand-made programming (project:Java, Java application) • Visual, component programming (project:Java, Java Desktop application) 4 Terminology Java Frame Panel Palette Microsoft Form Toolbox 5 Concept, Philosophy, Ideology Based on class libraries, grouped in packages When Java was introduced, GUI classes bundled in AWT library The AWT UI components were replaced by a more robust and flexible library, known as Swing components. To distinguish Swing components to their AWT counterparts, the Swing GUI components are named with a prefixed J. 6 The Java GUI API – 3 groups of classes Component classes – used for creating UI JButton, JLabel, JTextField, … Container classes – used to contain other components JFrame, JPanel, JApplet Helper classes – used to support GUI components. Graphics, Color, Font, FontMetrics, Dimension 7 GUI Class Hierarchy (Swing) Dimension Font Classes in the java.awt package LayoutManager 1 Heavyweight FontMetrics Object Color Panel Applet JApplet Window Frame JFrame Dialog JDialog Graphics Component Container * Swing Components in the javax.swing package JComponent Lightweight Swing GUI Components JCheckBoxMenuItem AbstractButton JComponent JMenuItem JMenu JButton JRadioButtonMenuItem JToggleButton JCheckBox JRadioButton JEditorPane JTextComponent JTextField JPasswordField JTextArea JLabel JTabbedPane JToolBar JTree JComboBox JList JSplitPane JMenuBar JTable JPanel JLayeredPane JPopupMenu JTableHeader JOptionPane JSeparator JFileChooser JInternalFrame JScrollBar JSlider JScrollPane JRootPane JColorChooser JProgressBar JToolTip JSpinner Frames To create a UI, you need a container, i.e. a frame. Frame is a window that is not contained inside another window. Frame is the basis to contain other user interface components in Java GUI applications. The JFrame class can be used to create windows. For Swing GUI programs, use JFrame class to create windows. 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); } } Frames javax.swing.JFrame +JFrame() Creates a default frame with no title. +JFrame(title: String) Creates a frame with the specified title. +setSize(width: int, height: int): void Specifies the size of the frame. +setLocation(x: int, y: int): void Specifies the upper-left corner location of the frame. +setVisible(visible: boolean): void Sets true to display the frame. +setDefaultCloseOperation(mode: int): void Specifies the operation when the frame is closed. +setLocationRelativeTo(c: Component): Sets the location of the frame relative to the specified component. void If the component is null, the frame is centered on the screen. +pack(): void Automatically sets the frame size to hold the components in the frame. Frames – To create empty frame Practice: Recommended IDE: NetBeans Create your own project: sbJavaWinEmptyForm • Hand-made programming (project:Java, Java application) Type import javax.swing.*; Type stmt within main() method to create a frame JFrame mySBForm = new JFrame("Empty Form"); Run the project • No frame appears on the screen Frames – To create empty frame Frame not visible if method setVisible() not invoked Add one more stmt mySBForm.setVisible(true); Do you see the form? Look at the top left corner of the screen Frames – To create empty frame Frame may move to the center of the screen using method setLocationRelativeTo() Add one more stmt mySBForm.setLocationRelativeTo(null); Do you see the form? Look at the screen center Frames – To create empty frame Frame sized to display just the title bar if method setSize() not used Add one more stmt mySBForm.setSize(900, 300); // dimensions in pixels Do you see the effect of the change? Hint: setSize() to invoke before invoking setLocationRelativeTo() Frames – To create empty frame How to tell the program to terminate when the frame gets closed? Add one more stmt mySBForm.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); If this stmt is not used, the program does not terminate when the frame is closed Adding components to a frame Modify the frame constructor argument JFrame mySBForm = new JFrame("Empty Form"); To JFrame mySBForm = new JFrame(“My frame with Components"); Adding components to a frame To add a component, we must : • Create a component • Add it to the frame (to the content pane of the frame) This may happen in Two steps • JLabel myLabel1 = new Jlabel(“This is not Empty Frame”); • mySBForm.add(myLabel1); Or in one step creating anonymous component • mySBForm.add(new JLabel(“This is not Empty Frame”)); Removing components from a frame To remove a component, we must use method remove(): • mySBForm.remove(myLabel1); Can we remove anonymous component? Adding two or more components to a frame To add more than one component, we must : • • • • • • JLabel myLabel1 = new Jlabel(“This is not Empty Frame”); mySBForm.add(myLabel1); JLabel myLabel2 = new Jlabel(“This is Frame with components”); mySBForm.add(myLabel2); //JButton myBtn1 = new JButton(“My Button”); //mySBForm.add(myBtn1); Do you see more than one component on the screen? No. What’s the problem? Adding two or more components to a frame This is because components are put in the frame by the content pane’s layout manager and the default layout manager if not specified explicitly, allocates all the frame to the current component replacing/substituting the previous component if there is any. It’s time to introduce several different layout managers to place components in the desired locations Frames – To create empty frame Practice: Recommended IDE: NetBeans Create your own project: sbJavaWinEmptyForm • Visual, component programming (project:Java, Java Desktop application) Use the toolbox facility to configure your project Run the project Layout Managers For more details open file LayoutManagersAndMore.ppt More on GUI programming Load file dialogs JFileChooser chooser = new JFileChooser(); chooser.setDialogTitle("Load which file?"); int result = chooser.showOpenDialog(enclosingJFrame); if (result != JFileChooser.APPROVE_OPTION) { File file = chooser.getSelectedFile(); // use file } You could also test for CANCEL_OPTION or ERROR_OPTION You will get back a File object; to use it, you must know how to do file I/O! 4/8/2015 Assoc. Prof. Stoyan Bonev 26 Save file dialogs JFileChooser chooser = new JFileChooser(); chooser.setDialogTitle(“Save file as?"); int result = chooser.showSaveDialog(enclosingJFrame); if (result != JFileChooser.APPROVE_OPTION) { File file = chooser.getSelectedFile(); // use file } You could also test for CANCEL_OPTION or ERROR_OPTION You will get back a File object; to use it, you must know how to do file I/O! 4/8/2015 Assoc. Prof. Stoyan Bonev 27 GUI Basics or Windows Based Applications 28 Motivations To build Windows application you need a frame (with title bar and content pane) structured to contain components/controls such as buttons, labels, text fields, check boxes, radio buttons, combo boxes, and others. See next slide for illustration 29 Creating GUI Objects Label Text field Check Box Button Combo Box // Create a button with text OK JButton jbtOK = new JButton("OK"); 30 Radio Button Creating GUI Objects Label Text field Check Box Radio Button Button Combo Box // Create a label with text "Enter your name: " JLabel jlblName = new JLabel("Enter your name: "); 31 Creating GUI Objects Label Text field Check Box Radio Button Button Combo Box // Create a text field with text "Type Name Here" JTextField jtfName = new JTextField("Type Name Here"); 32 Creating GUI Objects Label Text field Check Box Button Combo Box // Create a check box with text bold JCheckBox jchkBold = new JCheckBox("Bold"); 33 Radio Button Creating GUI Objects Label Text field Check Box Button Combo Box // Create a radio button with text red JRadioButton jrbRed = new JRadioButton("Red"); 34 Radio Button Creating GUI Objects Label Text field Check Box Button Combo Box // Create a combo box with choices red, green, and blue JComboBox jcboColor = new JComboBox(new String[]{"Red", "Green", "Blue"}); 35 Radio Button Creating GUI Objects // Create a button with text OK JButton jbtOK = new JButton("OK"); // Create a label with text "Enter your name: " JLabel jlblName = new JLabel("Enter your name: "); Label Text field Check Box Button // Create a text field with text "Type Name Here" JTextField jtfName = new JTextField("Type Name Here"); Combo Box // Create a check box with text bold JCheckBox jchkBold = new JCheckBox("Bold"); // Create a radio button with text red JRadioButton jrbRed = new JRadioButton("Red"); // Create a combo box with choices red, green, and blue JComboBox jcboColor = new JComboBox(new String[]{"Red", "Green", "Blue"}); 36 Radio Button Swing vs. AWT Swing class library OR AWT class library (Abstract Windows Toolkit) 37 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 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 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 components. 38 GUI Class Hierarchy (Swing) Dimension Font Classes in the java.awt package LayoutManager 1 Heavyweight FontMetrics Object Color Panel Applet JApplet Window Frame JFrame Dialog JDialog Graphics Component Container * Swing Components in the javax.swing package JComponent 39 Lightweight The Java GUI API The Java GUI API contains classes that may classify in three groups: Component classes Used to create interface Container classes Used to contain components Helper classes Used to support components 40 AWT (Optional) AWTEvent Font FontMetrics Object Color Graphics Component Container Panel Applet Button Window Frame Label TextField Dialog TextComponent TextArea List Choice CheckBox LayoutManager CheckBoxGroup Canvas MenuComponent MenuItem MenuBar Scrollbar 41 Menu FileDialog Frames To create a user interface, you need to create a frame. Frame is a window that is not contained inside another window. Frame is the basis to contain other user interface components in Java GUI applications. The JFrame class can be used to create windows. For Swing GUI programs, use JFrame class to create windows. 42 Creating Frames (open file ProgPureFrame.java) import javax.swing.*; public class MyFrame { public static void main(String[] args) { JFrame frame = new JFrame("Test Frame"); frame.setSize(400,300); frame.setLocationRelativeTo(null); frame.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE); frame.setVisible(true); } 43 } Adding Components into a Frame Title bar // Add a button into the frame frame.getContentPane().add( new JButton("OK")); Content pane 44 Content Pane Delegation in JDK 1.5 Title bar Content pane // Add a button into the frame frame.getContentPane().add( new JButton("OK")); // Add a button into the frame frame.add( new JButton("OK") ); 45 JFrame Class javax.swing.JFrame +JFrame() Creates a default frame with no title. +JFrame(title: String) Creates a frame with the specified title. +setSize(width: int, height: int): void Specifies the size of the frame. +setLocation(x: int, y: int): void Specifies the upper-left corner location of the frame. +setVisible(visible: boolean): void Sets true to display the frame. +setDefaultCloseOperation(mode: int): void Specifies the operation when the frame is closed. +setLocationRelativeTo(c: Component): void Sets the location of the frame relative to the specified component. If the component is null, the frame is centered on the screen. +pack(): void Automatically sets the frame size to hold the components in the frame. Demo: Open file ProgFrameAndControls.java 46 Demo – different source text structure – same functionality Open file ProgFrameAndControls.java Open file ProgFrameAndControlsStyleStandard.java Open file ProgFrameAndControlsStyleRecommended.java Open file ProgFrameAndControlsStyleSeparateClasses.java 47 Demo Open file ProgFrameAndControls.java You cannot visualize more than one component. Each new component replaces the previous one The component occupies all the frame space How to proceed with more components? You need a layout manager to associate with the container using method setLayout() in context <container>.setLayout(<arg>); 48 Layout Managers Java’s layout managers provide a level of abstraction to automatically map your user interface on all window systems. The UI components are placed in containers. Each container has a layout manager to arrange the UI components within the container. Layout managers are set in containers using the setLayout(LayoutManager) method in a container. 49 Kinds of Layout Managers FlowLayout GridLayout BorderLayout Several other layout managers will be introduced in Chapter 33, “Containers, Layout Managers, and Borders” 50 FlowLayout Example The simplest layout manager. Components arranged from left to right row by row in the order in which they were added. Possible alignment control Demo: file ProgFrameAndLayout.java 51 NetBeans – functionality Introduction to GUI Building Contents Exercise 1: Creating a Project Exercise 2: Building the Front End Exercise 3: Adding Functionality Exercise 4: Running the Program How Event Handling Works 52 Exercises/Tasks Try to run ProgFrameAndLayout.java program 53 FlowLayout Example Run the ProgFrameAndLayout.java program as it is set without layout manager: // // // // with and/or without frame.setLayout(new frame.setLayout(new frame.setLayout(new layout manager FlowLayout(FlowLayout.LEFT,10,20)); GridLayout( 3, 2, 10, 15)); BorderLayout( 10, 20)); 54 FlowLayout Example Run the ProgFrameAndLayout.java program as it is set with FlowLayout layout manager: // with and/or without frame.setLayout(new // frame.setLayout(new // frame.setLayout(new layout manager FlowLayout(FlowLayout.LEFT,10,20)); GridLayout( 3, 2, 10, 15)); BorderLayout( 10, 20)); 55 FlowLayout Example Write a program that adds three labels and text fields into the content pane of a frame with a FlowLayout manager. 56 The FlowLayout Class java.awt.FlowLayout The get and set methods for these data fields are provided in the class, but omitted in the UML diagram for brevity. -alignment: int The alignment of this layout manager (default: CENTER). -hgap: int The horizontal gap of this layout manager (default: 5 pixels). -vgap: int The vertical gap of this layout manager (default: 5 pixels). +FlowLayout() Creates a default FlowLayout manager. +FlowLayout(alignment: int) Creates a FlowLayout manager with a specified alignment. +FlowLayout(alignment: int, hgap: int, vgap: int) Creates a FlowLayout manager with a specified alignment, horizontal gap, and vertical gap. 57 GridLayout Example Components arranged in a grid (matrix) formation. from left to right row by row in the order in which they were added. Demo: file ProgFrameAndLayout.java 58 GridLayout Example Run the ProgFrameAndLayout.java program as it is set with GridLayout layout manager: // with and/or without // frame.setLayout(new frame.setLayout(new // frame.setLayout(new layout manager FlowLayout(FlowLayout.LEFT,10,20)); GridLayout( 3, 2, 10, 15)); BorderLayout( 10, 20)); 59 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. 60 The GridLayout Class java.awt.GridLayout The get and set methods for these data fields are provided in the class, but omitted in the UML diagram for brevity. -rows: int The number of rows in this layout manager (default: 1). -columns: int The number of columns in this layout manager (default: 1). -hgap: int The horizontal gap of this layout manager (default: 0). -vgap: int The vertical gap of this layout manager (default: 0). +GridLayout() 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. 61 The BorderLayout Manager add(Component, constraint), where constraint is BorderLayout.EAST, BorderLayout.SOUTH, BorderLayout.WEST, BorderLayout.NORTH, or BorderLayout.CENTER. The BorderLayout manager divides the container into five areas: East, South, West, North, and Center. Components are added to a BorderLayout by using the add method. 62 BorderLayout Example File ProgFrameAndLayout.java 63 BorderLayout Example Run the ProgFrameAndLayout.java program as it is set with BorderLayout layout manager: // with and/or without // frame.setLayout(new // frame.setLayout(new frame.setLayout(new layout manager FlowLayout(FlowLayout.LEFT,10,20)); GridLayout( 3, 2, 10, 15)); BorderLayout( 10, 20)); // uncomment this text frame.add(jbtOK1, frame.add(jbtOK2, frame.add(jbtOK3, frame.add(jbtOK4, frame.add(jbtOK5, BorderLayout.EAST); BorderLayout.CENTER); BorderLayout.WEST); BorderLayout.NORTH); BorderLayout.SOUTH); 64 The BorderLayout Class java.awt.BorderLayout The get and set methods for these data fields are provided in the class, but omitted in the UML diagram for brevity. -hgap: int The horizontal gap of this layout manager (default: 0). -vgap: int The vertical gap of this layout manager (default: 0). +BorderLayout() Creates a default BorderLayout manager. +BorderLayout(hgap: int, vgap: int) Creates a BorderLayout manager with a specified number of horizontal gap, and vertical gap. 65 The Color Class 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. 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); 66 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. 67 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.setForeground(Color.red); 68 The Font Class Font Names Font Style Standard font names that are supported in all platforms are: SansSerif, Serif, Monospaced, Dialog, or DialogInput. 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); 69 Finding All Available Font Names GraphicsEnvironment e = GraphicsEnvironment.getLocalGraphicsEnvironment(); String[] fontnames = e.getAvailableFontFamilyNames(); for (int i = 0; i < fontnames.length; i++) System.out.println(fontnames[i]); 70 Using Panels as Sub-Containers Panels act as sub-containers for grouping user interface components. It is recommended that you place the user interface components in panels and place the panels in a frame. You can also place panels in a panel. To add a component to JFrame, you actually add it to the content pane of JFrame. To add a component to a panel, you add it directly to the panel using the .add method. 71 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")); 72 Demo Open file ProgTestPanels.java Open file ProgTestPanels2.java 73 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 74 Common Features of Swing Components java.awt.Component The get and set methods for these data fields are provided in the class, but omitted in the UML diagram for brevity. -font: java.awt.Font The font of this component. -background: java.awt.Color The background color of this component. -foreground: java.awt.Color The foreground color of this component. -preferredSize: Dimension The preferred size of this component. -visible: boolean Indicates whether this component is visible. +getWidth(): int Returns the width of this component. +getHeight(): int Returns the height of this component. +getX(): int getX() and getY() return the coordinate of the component’s upper-left corner within its parent component. +getY(): int 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 Returns the layout manager for this container. +setLayout(l: LayoutManager): void Sets the layout manager for this container. +paintComponents(g: Graphics): void 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 -toolTipText: String The tool tip text for this component. Tool tip text is displayed when the mouse points on the component without clicking. -border: javax.swing.border.Border The border for this component. 75 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). To create a line border, use new LineBorder(Color color, int width), 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 TitledBorder(“My Panel”)); 76 Test Swing Common Features Component Properties JComponent Properties toolTipText font background foreground preferredSize minimumSize maximumSize border 77 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 78 Run Splash Screen A splash screen is an image that is displayed while the application is starting up. If your program takes a long time to load, you may display a splash screen to alert the user. For example, the following command: java –splash:image/us.gf TestImageIcon displays an image while the program TestImageIcon is being loaded. 79 Task Write JAVA program to support a frame with three labels Three text fields Two buttons Scheme of the pane: label1 label2 label3 button1 textfield1 textfield2 textfield3 button2 Questions? And/Or Thank You For Your Attention! 81