15slide_2007 - Chapter 15 Creating User Interfaces...

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Unformatted text preview: Chapter 15 Creating User Interfaces EE3206/EE5805 Java Programming & Applications 1 Objectives To create graphical user interfaces with various user-interface To components: JButton, JCheckBox, JRadioButton, JLabel, JTextField, JTextArea, JComboBox, JList, JScrollBar, and JSlider. To create listeners for various types of events. To To use borders to visually group user-interface components. To To create image icons using the ImageIcon class. To To display multiple windows in an application. To EE3206/EE5805 Java Programming & Applications 2 Components Covered in the Chapter Introduces the frequently used GUI components Introduces Uses borders and icons Uses JButton Component Container JComponent AbstractButton JToggleButton JLabel JTextArea JTextComponent JTextField JComboBox JList JScrollBar JSlider JCheckBox JRadioButton JPasswordField EE3206/EE5805 Java Programming & Applications 3 Buttons A button is a component that triggers an action event button when clicked. Swing provides regular buttons, toggle buttons, check Swing box buttons, and radio buttons. The common features of these buttons are The generalized in javax.swing.AbstractButton. EE3206/EE5805 Java Programming & Applications 4 AbstractButton javax.swing.JComponent javax.swing.AbstractButton -actionCommand: String -text: String -icon: javax.swing.Icon -pressedIcon: javax.swing.Icon -rolloverIcon: javax.swing.Icon -mnemonic: int -horizontalAlignment: int -horizontalTextPosition: int -verticalAlignment: int -verticalTextPosition: int -borderPainted: boolean The action command of this button. The button’s text (i.e., the text label on the button). The button’s default icon. This icon is also used as the "pressed" and "disabled" icon if there is no explicitly set pressed icon. The pressed icon (displayed when the button is pressed). The rollover icon (displayed when the mouse is over the button). The mnemonic key value of this button. You can select the button by pressing the ALT key and the mnemonic key at the same time. The horizontal alignment of the icon and text (default: CENTER). The horizontal text position relative to the icon (default: RIGHT). The vertical alignment of the icon and text (default: CENTER). The vertical text position relative to the icon (default: CENTER). Indicates whether the border of the button is painted. By default, a regular button’s border is painted, but the borders for a check box and a radio button is not painted. The gap between the text and the icon on the button (JDK 1.4). The state of the button. True if the check box or radio button is selected, false if it's not. EE3206/EE5805 Java Programming & Applications 5 The get and set methods for these data fields are provided in the class, but omitted in the UML diagram for brevity. -iconTextGap: int -selected(): boolean JButton JButton inherits AbstractButton and provides several constructors to create buttons. javax.swing.AbstractButton javax.swing.JButton +JButton() +JButton(icon: javax.swing.Icon) +JButton(text: String) +JButton(text: String, icon: Icon) Creates a default button with no text and icon. Creates a button with an icon. Creates a button with text. Creates a button with text and an icon. EE3206/EE5805 Java Programming & Applications 6 JButton Constructors and Properties JButton() JButton JButton(String text) JButton(String JButton(String text, Icon icon) JButton(String JButton(Icon icon) JButton(Icon text text icon icon mnemonic mnemonic horizontalAlignment horizontalAlignment verticalAlignment verticalAlignment horizontalTextPosition horizontalTextPosition verticalTextPosition verticalTextPosition iconTextGap iconTextGap EE3206/EE5805 Java Programming & Applications 7 Default Icons, Pressed Icon, and Rollover Icon A regular button has a default icon, pressed icon, and rollover icon. Normally, you use the default icon. All other icons are for special effects. A pressed icon is displayed when a button is pressed and a rollover icon is displayed when the mouse is over the button but not pressed. (A) Default icon (B) Pressed icon (C) Rollover icon Run TestButtonIcons EE3206/EE5805 Java Programming & Applications 8 Horizontal Alignments Horizontal alignment specifies how the icon and text are placed Horizontal horizontally on a button. You can set the horizontal alignment using one of the five constants: You LEADING, LEFT, CENTER, RIGHT, TRAILING. At present, LEADING and LEFT are the same and TRAILING and RIGHT are the same. The default horizontal alignment is SwingConstants.TRAILING. The EE3206/EE5805 Java Programming & Applications 9 Vertical Alignments Vertical alignment specifies how the icon and text are placed vertically Vertical on a button. You can set the vertical alignment using one of the three constants: TOP, CENTER, BOTTOM. The default vertical alignment is SwingConstants.CENTER. The EE3206/EE5805 Java Programming & Applications 10 Horizontal Text Positions Horizontal text position specifies the horizontal position of the text Horizontal relative to the icon. You can set the horizontal text position using one of the five constants: You LEADING, LEFT, CENTER, RIGHT, TRAILING. The default horizontal text position is SwingConstants.RIGHT. The EE3206/EE5805 Java Programming & Applications 11 Vertical Text Positions Vertical text position specifies the vertical position of the text relative Vertical to the icon. You can set the vertical text position using one of the three constants: You TOP, CENTER. The default vertical text position is SwingConstants.CENTER. The EE3206/EE5805 Java Programming & Applications 12 Example: Using Buttons Write a program that displays a message on a panel and uses two buttons, <= and =>, to move the message on the panel to the left or right. ButtonDemo Run MessagePanel JButton JButton EE3206/EE5805 Java Programming & Applications 13 JCheckBox JCheckBox inherits all the properties such as text, icon, mnemonic, verticalAlignment, horizontalAlignment, horizontalTextPosition, verticalTextPosition, and selected from AbstractButton, and provides several constructors to create check boxes. javax.swing.AbstractButton javax.swing.JToggleButton javax.swing.JCheckBox +JCheckBox() +JCheckBox(text: String) +JCheckBox(text: String, selected: boolean) +JCheckBox(icon: Icon) +JCheckBox(text: String, icon: Icon) +JCheckBox(text: String, icon: Icon, selected: boolean) Creates a default check box button with no text and icon. Creates a check box with text. Creates a check box with text and specifies whether the check box is initially selected. Creates a checkbox with an icon. Creates a checkbox with text and an icon. Creates a check box with text and an icon, and specifies whether the check box is initially selected. 14 EE3206/EE5805 Java Programming & Applications Example: Using Check Boxes Add three check boxes named Centered, Bold, and Italic into the Centered Bold Italic previous example to let the user specify whether the message is centered, bold, or italic. ButtonDemo CheckBoxDemo Run CheckBoxDemo EE3206/EE5805 Java Programming & Applications 15 JRadioButton Radio buttons are variations of check boxes. They are often used in the group, where only one button is checked at a time. They can be grouped with the following code: ButtonGroup btg = new ButtonGroup(); btg.add(jrb1); btg.add(jrb2); javax.swing.AbstractButton j avax.swing.JToggleButton j avax.swing.JRadioButton + JRadioButton() +JRadioButton(text: String) +JRadioButton(text: String, selected: boolean) +JRadioButton(icon: Icon) +JRadioButton(text: String, icon: Icon) +JRadioButton(text: String, icon: Icon, selected: boolean) C reates a default radio button with no text and icon. Creates a radio button with text. Creates a radio button with text and specifies whether the radio button is initially selected. Creates a radio button with an icon. Creates a radio button with text and an icon. Creates a radio button with text and an icon, and specifies whether the radio button is initially selected. 16 EE3206/EE5805 Java Programming & Applications Example: Using Radio Buttons Add three radio buttons named Red, Green, and Blue Red Green Blue into the preceding example to let the user choose the color of the message. ButtonDemo RadioButtonDemo Run CheckBoxDemo RadioButtonDemo EE3206/EE5805 Java Programming & Applications 17 JLabel A label is a display area for a short text, an image, or both. is javax.swing.JComponent javax.swing.JLabel -text: String -icon: javax.swing.Icon -horizontalAlignment: int -horizontalTextPosition: int -verticalAlignment: int -verticalTextPosition: int -iconTextGap: int +JLabel() +JLabel(icon: javax.swing.Icon) +JLabel(icon: Icon, hAlignment: int) +JLabel(text: String) +JLabel(text: String, icon: Icon, hAlignment: int) +JLabel(text: String, hAlignment: int) The label’s text. The label’s image icon. The horizontal alignment of the text and icon on the label. The horizontal text position relative to the icon on the label. The vertical alignment of the text and icon on the label. The vertical text position relative to the icon on the label. The gap between the text and the icon on the label (JDK 1.4). Creates a default label with no text and icon. Creates a label with an icon. Creates a label with an icon and the specified horizontal alignment. Creates a label with text. Creates a label with text, an icon, and the specified horizontal alignment. Creates a label with text and the specified horizontal alignment. 18 The get and set methods for these data fields are provided in the class, but omitted in the UML diagram for brevity. EE3206/EE5805 Java Programming & Applications JLabel Constructors & Properties The constructors for labels are as follows: JLabel() JLabel(String text, int horizontalAlignment) JLabel(String text) JLabel(Icon icon) JLabel(Icon icon, int horizontalAlignment) JLabel(String text, Icon icon, int horizontalAlignment) JLabel inherits all the properties from JComponent and has many properties similar to the ones in JButton, such as text, icon, horizontalAlignment, verticalAlignment, horizontalTextPosition, verticalTextPosition, and iconTextGap. EE3206/EE5805 Java Programming & Applications 19 Using Labels // Create an image icon from image file ImageIcon icon = new ImageIcon("image/grapes.gif"); // Create a label with text, // an icon, with centered horizontal alignment JLabel jlbl = new JLabel("Grapes", icon, SwingConstants.CENTER); // Set label's text alignment and gap between text and icon jlbl.setHorizontalTextPosition(SwingConstants.CENTER); jlbl.setVerticalTextPosition(SwingConstants.BOTTOM); jlbl.setIconTextGap(5); EE3206/EE5805 Java Programming & Applications 20 JTextField A text field is an input area where the user can type in characters. Text text fields are useful in that they enable the user to enter in variable data (such as a name or a description). javax.swing.text.JTextComponent -text: String -editable: boolean The get and set methods for these data fields are provided in the class, but omitted in the UML diagram for brevity. The text contained in this text component. Indicates whether this text component is editable (default: true). javax.swing.JTextField -columns: int -horizontalAlignment: int +JTextField() +JTextField(column: int) +JTextField(text: String) +JTextField(text: String, columns: int) The number of columns in this text field. The horizontal alignment of this text field (default: LEFT). Creates a default empty text field with number of columns set to 0. Creates an empty text field with specified number of columns. Creates a text field initialized with the specified text. Creates a text field initialized with the specified text and columns. EE3206/EE5805 Java Programming & Applications 21 JTextField Constructors & Properties JTextField(int columns) JTextField(int Creates an empty text field with the specified number of columns. JTextField(String text) JTextField(String Creates a text field initialized with the specified text. JTextField(String text, int columns) JTextField(String Creates a text field initialized with the specified text and the column size. text text horizontalAlignment horizontalAlignment editable editable columns columns EE3206/EE5805 Java Programming & Applications 22 JTextField Methods getText() getText Returns the string from the text field. setText(String text) setText(String Puts the given string in the text field. setEditable(boolean editable) setEditable(boolean Enables or disables the text field to be edited. By default, editable is true. editable setColumns(int) setColumns(int Sets the number of columns in this text field. The length of the text field is changeable. EE3206/EE5805 Java Programming & Applications 23 Example: Using Text Fields Add a text field to the preceding example to let the user set a new message. JFrame ButtonDemo CheckBoxDemo RadioButtonDemo TextFieldDemo TextFieldDemo Run EE3206/EE5805 Java Programming & Applications 24 JTextArea If you want to let the user enter multiple lines of text, you cannot use text fields unless you create several of them. The solution is to use JTextArea, which enables the user to enter multiple lines of text. JTextArea javax.swing.text.JTextComponent javax.swing.JTextArea -columns: int -rows: int -tabSize: int -lineWrap: boolean -wrapStyleWord: boolean +JTextArea() +JTextArea(rows: int, columns: int) +JTextArea(text: String) The number of columns in this text area. The number of rows in this text area. The number of characters used to expand tabs (default: 8). Indicates whether the line in the text area is automatically wrapped (default: false). Indicates whether the line is wrapped on words or characters (default: false). Creates a default empty text area. Creates an empty text area with the specified number of rows and columns. Creates a new text area with the specified text displayed. The get and set methods for these data fields are provided in the class, but omitted in the UML diagram for brevity. +JTextArea(text: String, rows: int, columns: int) Creates a new text area with the specified text and number of rows and columns. Appends the string to text in the text area. +append(s: String): void +insert(s: String, pos: int): void +replaceRange(s: String, start: int, end: int): void +getLineCount(): int Inserts string s in the specified position in the text area. Replaces partial text in the range from position start to end with string s. Returns the actual number of lines contained in the text area. EE3206/EE5805 Java Programming & Applications 25 JTextArea Constructors & Properties JTextArea(int rows, int columns) JTextArea(int Creates a text area with the specified number of rows and columns. JTextArea(String s, int rows, int columns) JTextArea(String Creates a text area with the initial text and the number of rows and columns specified. text text editable editable columns columns lineWrap lineWrap wrapStyleWord wrapStyleWord rows rows lineCount lineCount tabSize tabSize EE3206/EE5805 Java Programming & Applications 26 Example: Using Text Areas This example gives a program that displays an image in a label, This a title in a label, and a text in a text area. TextAreaDemo Run JPanel JFrame DescriptionPanel -jlblImage: JLabel -jtaTextDescription: JTextArea +setImageIcon(icon: ImageIcon): void +setTitle(title: String): void +setTextDescription(text: String): void +getMinimumSize(): Dimension 1 1 TextAreaDemo EE3206/EE5805 Java Programming & Applications 27 JComboBox A combo box is a simple list of items from which the user can combo choose. It performs basically the same function as a list, but can get only one value. javax.swing.JComponent javax.swing.JComboBox +JComboBox() +JComboBox(items: Object) +addItem(item: Object): void +getItemAt(index: int): Object +getItemCount(): int +getSelectedIndex(): int +setSelectedIndex(index: int): void +getSelectedItem(): Object +setSelectedItem(item: Object): void Creates a default empty combo box. Creates a combo box that contains the elements in the specified array. Adds an item to the combo box. Returns the item at the specified index. Returns the number of items in the combo box. Returns the index of the selected item. Sets the selected index in the combo box. Returns the selected item. Sets the selected item in the combo box. +removeItem(anObject: Object): void Removes an item from the item list. Removes the item at the specified index in the combo box. +removeItemAt(anIndex: int): void +removeAllItems(): void Removes all items in the combo box. EE3206/EE5805 Java Programming & Applications 28 JComboBox Methods and Event Handler To add an item to a JComboBox jcbo, use JComboBox To jcbo.addItem(Object item) To get an item from JComboBox jcbo, use JComboBox To jcbo.getItem() When a choice is checked or unchecked, the itemStateChanged() handler for ItemEvent is invoked as well as the actionPerformed() handler for ActionEvent. public void itemStateChanged(ItemEvent e) { // Make sure the source is a combo box if (e.getSource() instanceof JComboBox) String s = (String)e.getItem(); } EE3206/EE5805 Java Programming & Applications 29 Example: Using Combo Boxes This example lets users view an image and a description of a country's flag by selecting the country from a combo box. ComboBoxDemo Run EE3206/EE5805 Java Programming & Applications 30 JList A list is a component that performs basically the same function as a combo list box, but it enables the user to choose a single value or multiple values. javax.swing.JComponent javax.swing.JList +JList() +JList(items: Object) +getSelectedIndex(): int +setSelectedIndex(index: int): void +getSelectedIndices(): int Creates a default empty list. Creates a list that contains the elements in the specified array. Returns the index of the first selected item. Selects the cell at the specified index. Returns an array of all of the selected indices in increasing order. +setSelectedIndices(indices: int): void Selects the cells at the specified indices. +getSelectedValue(): Object Returns the first selected item in the list. +getSelectedValues(): Object +getVisibleRowCount(): int +setVisibleRowCount(count: int): void +getSelectionBackground(): Color Returns an array of the values for the selected cells in increasing index order. Returns the number of visible rows displayed without a scrollbar. (default: 8) Sets the preferred number of visible rows displayed without a scrollbar. Returns the background color of the selected cells. +setSelectionBackground(c: Color): void Sets the background color of the selected cells. +getSelectionForeground(): Color Returns the foreground color of the selected cells. +setSelectionForeground(c: Color): void Sets the foreground color of the selected cells. +getSelectionMode(): int Returns the selection mode for the list. EE3206/EE5805 Java Programming & Applications 31 JList Constructors & Properties JList() JList Creates an empty list. JList(Object stringItems) JList(Object Creates a new list initialized with items. selectedIndexd selectedIndexd selectedIndices selectedIndices selectedValue selectedValue selectedValues selectedValues selectionMode selectionMode visibleRowCount visibleRowCount EE3206/EE5805 Java Programming & Applications 32 Example: Using Lists This example gives a program that lets users select countries in a list and display the flags of the selected countries in the labels. ListDemo EE3206/EE5805 Java Programming & Applications Run 33 JScrollBar A scroll bar is a control that enables the user to select from a range of values. The scroll scrollbar appears in two styles: horizontal and vertical. horizontal vertical javax.swing.JComponent j avax.swing.JScrollBar -orientation: int -maximum: int Specifies horizontal or vertical style, default is horizontal. Specifies the maximum value the scroll bar represents when the bubble reaches the right end of the scroll bar for horizontal style or the bottom of the scroll bar for vertical style. Specifies the minimum value the scroll bar represents when the bubble reaches the left end of the scroll bar for horizontal style or the top of the scroll bar for vertical style. Specifies the relative width of the scroll bar's bubble. The actual width appearing on the screen is determined by the maximum value and the value of visibleAmount. Represents the current value of the scroll bar. Specifies value added (subtracted) when the user activates the blockincrement (decrement) area of the scroll bar, as shown in Figure 13.30. Specifies the value added (subtracted) when the user activates the unitincrement (decrement) area of the scroll bar, as shown in Figure 13.30. Creates a default vertical scroll bar. Creates a scroll bar with the specified orientation. The get and set methods for these data fields are provided in the class, but omitted in the UML diagram for brevity. -minimum: int -visibleAmount: int -value: int -blockIncrement: int -unitIncrement: int +JScrollBar() +JScrollBar(orientation: int) +JScrollBar(orientation: int, value: Creates a scrollbar with the specified orientation, value, extent, int, extent: int, min: int, max: int) minimum, and maximum. EE3206/EE5805 Java Programming & Applications 34 Scroll Bar Properties Minimal value Block decrement Maximal value Block increment Bubble Unit decrement Unit increment EE3206/EE5805 Java Programming & Applications 35 Example: Using Scrollbars This example uses horizontal and vertical scrollbars to control a message displayed on a panel. The horizontal scrollbar is used to move the message to the left or the right, and the vertical scrollbar to move it up and down. ScrollBarDemo Run EE3206/EE5805 Java Programming & Applications 36 JSlider JSlider is similar to JScrollBar, but JSlider has more properties and can appear in many forms. javax.swing.JComponent javax.swing.JSlider -maximum: int -minimum: int -value: int -orientation: int -paintLabels: boolean -paintTicks: boolean -paintTrack: boolean -majorTickSpacing: int -minorTickSpacing: int -inverted: boolean +JSlider() +JSlider(min: int, max: int) +JSlider(min: int, max: int, value: int) +JSlider(orientation: int) +JSlider(orientation: int, min: int, max: int, value: int) The maximum value represented by the slider (default: 100). The minimum value represented by the slider (default: 0). The current value represented by the slider. The orientation of the slider (default: JSlider.HORIZONTAL). True if the labels are painted at tick marks (default: false). True if the ticks are painted on the slider (default: false). True if the track is painted on the slider (default: true). The number of units between major ticks (default: 0). The number of units between minor ticks (default: 0). True to reverse the value-range, and false to put the value range in the normal order (default: false). Creates a default horizontal slider. Creates a horizontal slider using the specified min and max. Creates a horizontal slider using the specified min, max, and value. Creates a slider with the specified orientation. Creates a slider with the specified orientation, min, max, and value. The get and set methods for these data fields are provided in the class, but omitted in the UML diagram for brevity. EE3206/EE5805 Java Programming & Applications 37 Example: Using Sliders Rewrite the preceding program using the sliders to control a message displayed on a panel instead of using scroll bars. SliderDemo Run EE3206/EE5805 Java Programming & Applications 38 Creating Multiple Windows The following slides show step-by-step how to create an additional window from an application or applet. Step 1: Create a subclass of JFrame (called a SubFrame) that tells the new JFrame SubFrame window what to do. For example, all the GUI application programs extend JFrame and are subclasses of JFrame. JFrame JFrame Step 2: Create an instance of SubFrame in the application or applet. SubFrame Example: SubFrame subFrame = new SubFrame("SubFrame Title"); EE3206/EE5805 Java Programming & Applications 39 Creating Multiple Windows Step 3: Create a JButton for activating the subFrame. JButton subFrame add(new JButton("Activate SubFrame")); Step 4: Override the actionPerformed() method to make the actionPerformed additional window visible as follows: public actionPerformed(ActionEvent e) { String actionCommand = e.getActionCommand(); if ("Activate SubFrame".equals(actionCommand)) { subFrame.setVisible(true); } } EE3206/EE5805 Java Programming & Applications 40 Example: Creating Multiple Windows This example creates a main window with a text area in the scroll pane, and a This button named "Show Histogram." When the user clicks the button, a new window appears that displays a histogram to show the occurrence of the letters in the text area. MultipleWindowsDemo Run Histogram EE3206/EE5805 Java Programming & Applications 41 ...
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