1、第15讲. 图像界面组件,常用用户界面组件,JButton 按钮jbt JCheckBox 复选框jchk JRadioButton 单选框jrb JLabel 标签 jlbl JTextField 文本域 jtf JTextArea 文本区域 jta JComboBox 组合框 jcbo JList 列表 jlst,GUI Class Hierarchy (Swing) GUI类的继承关系,常用用户界面组件,Java事件对象的层次结构,用户行为、源对象和事件 对应关系,Source Event Type User Action Object GeneratedClick a button点击
2、按钮 JButton ActionEvent Click a check box点击复选框 JCheckBox ItemEvent, ActionEvent Click a radio button单击单选框 JRadioButton ItemEvent, ActionEvent Press return on a text field文本回车 JTextField ActionEvent Select a new item选一个新项 JComboBox ItemEvent, ActionEvent Select a list new item 选多项 JList JSelectionList
3、Event Window opened, closed, etc. Window WindowEvent Mouse pressed, released, etc. Component MouseEvent Key released, pressed, etc. Component KeyEvent,AbstractButton,1 JButton,JButton Constructors 构造方法,The following are JButton constructors: JButton() JButton(String text) JButton(String text, Icon i
4、con) JButton(Icon icon),JButton Properties 常用属性,text icon mnemonic horizontalAlignment verticalAlignment horizontalTextPosition verticalTextPosition,Default Icons, Pressed Icon, and Rollover Icon 默认图标、按下图标和翻转图标,A regular button has a default icon, pressed icon, and rollover icon. Normally, you use t
5、he 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,Demo TestButtonIcons.java,import javax.swing.*; publi
6、c class TestButtonIcons extends JFrame public static void main(String args) / Create a frame and set its properties JFrame frame = new TestButtonIcons();frame.setTitle(“ButtonIcons“);frame.setSize(165, 80);frame.setLocationRelativeTo(null); / Center the frameframe.setDefaultCloseOperation(JFrame.EXI
7、T_ON_CLOSE);frame.setVisible(true); public TestButtonIcons() ImageIcon usIcon = new ImageIcon(“image/usIcon.gif“);ImageIcon caIcon = new ImageIcon(“image/caIcon.gif“); ImageIcon ukIcon = new ImageIcon(“image/ukIcon.gif“);JButton jbt = new JButton(“Click it“, usIcon);jbt.setPressedIcon(caIcon);jbt.se
8、tRolloverIcon(ukIcon);add(jbt); ,Horizontal Alignments 水平对齐,Horizontal alignment specifies how the icon and text are placed horizontally on a button. You can set the horizontal alignment using one of the five constants: LEADING, LEFT, CENTER, RIGHT, TRAILING. At present, LEADING and LEFT are the sam
9、e and TRAILING and RIGHT are the same. Future implementation may distinguish them. The default horizontal alignment is SwingConstants.TRAILING.,Vertical Alignments 垂直对齐,Vertical alignment specifies how the icon and text are placed vertically on a button. You can set the vertical alignment using one
10、of the three constants: TOP, CENTER, BOTTOM. The default vertical alignment is SwingConstants.CENTER.,Horizontal Text Positions 文本水平,Horizontal text position specifies the horizontal position of the text relative to the icon. You can set the horizontal text position using one of the five constants:
11、LEADING, LEFT, CENTER, RIGHT, TRAILING. The default horizontal text position is SwingConstants.RIGHT.,Vertical Text Positions 文本垂直,Vertical text position specifies the vertical position of the text relative to the icon. You can set the vertical text position using one of the three constants: TOP, CE
12、NTER. The default vertical text position is SwingConstants.CENTER.,JButton触发事件,当按钮回车时，触发一个ActionEvent。,Example: Using Buttons,Write a program that displays a message on a panel and uses two buttons, , to move the message on the panel to the left or right.,触发ActionEvent,import java.awt.*; import java
13、.awt.event.ActionListener; import java.awt.event.ActionEvent; import javax.swing.*;public class ButtonDemo extends JFrame / Create a panel for displaying messageprotected MessagePanel messagePanel= new MessagePanel(“Welcome to Java“);/ Declare two buttons to move the message left and rightprivate JB
14、utton jbtLeft = new JButton(“);public static void main(String args) ButtonDemo frame = new ButtonDemo();frame.setTitle(“ButtonDemo“);frame.setLocationRelativeTo(null); / Center the frameframe.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);frame.setSize(500, 200);frame.setVisible(true);public ButtonD
15、emo() / Set the background color of messagePanelmessagePanel.setBackground(Color.white);/ Create Panel jpButtons to hold two Buttons “JPanel jpButtons = new JPanel();jpButtons.setLayout(new FlowLayout();jpButtons.add(jbtLeft);jpButtons.add(jbtRight);/ Set keyboard mnemonicsjbtLeft.setMnemonic(L);jbt
16、Right.setMnemonic(R);/ Set icons and remove text / jbtLeft.setIcon(new ImageIcon(“image/left.gif“); / jbtRight.setIcon(new ImageIcon(“image/right.gif“); / jbtLeft.setText(null); / jbtRight.setText(null);/ Set tool tip text on the buttonsjbtLeft.setToolTipText(“Move message to left“);jbtRight.setTool
17、TipText(“Move message to right“);/ Place panels in the framesetLayout(new BorderLayout();add(messagePanel, BorderLayout.CENTER);add(jpButtons, BorderLayout.SOUTH);/ Register listeners with the buttonsjbtLeft.addActionListener(new ActionListener() public void actionPerformed(ActionEvent e) messagePan
18、el.moveLeft(););jbtRight.addActionListener(new ActionListener() public void actionPerformed(ActionEvent e) messagePanel.moveRight();); ,Demo ButtonDemo .java,2 JCheckBox 复选框,JCheckBox inherits all the properties such as text, icon, mnemonic, verticalAlignment, horizontalAlignment, horizontalTextPosi
19、tion, verticalTextPosition, and selected from AbstractButton, and provides several constructors to create check boxes.,JCheckBox触发事件,当复选框被点击（选中或未选中）时，先触发一个ItemEvent,然后触发一个ActionEvent。要确定是否选中，用isSelected()方法，返回true表示被选中。 对于监听器的设置，可以选用ItemEvent 或者ActionEvent 两者之一。,Example: Using Check Boxes,Add three
20、check boxes named Centered, Bold, and Italic into Example 15.1 to let the user specify whether the message is centered, bold, or italic.,ButtonDemo,CheckBoxDemo,import java.awt.*; import java.awt.event.*; import javax.swing.*;public class CheckBoxDemo extends ButtonDemo / Create three check boxes to
21、 control the display of messageprivate JCheckBox jchkCentered = new JCheckBox(“Centered“);private JCheckBox jchkBold = new JCheckBox(“Bold“);private JCheckBox jchkItalic = new JCheckBox(“Italic“);public static void main(String args) CheckBoxDemo frame = new CheckBoxDemo();frame.setTitle(“CheckBoxDem
22、o“);frame.setLocationRelativeTo(null); / Center the frameframe.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);frame.setSize(500, 200);frame.setVisible(true);public CheckBoxDemo() / Set mnemonic keysjchkCentered.setMnemonic(C);jchkBold.setMnemonic(B);jchkItalic.setMnemonic(I);/ Create a new panel to
23、hold check boxesJPanel jpCheckBoxes = new JPanel();jpCheckBoxes.setLayout(new GridLayout(3, 1);jpCheckBoxes.add(jchkCentered);jpCheckBoxes.add(jchkBold);jpCheckBoxes.add(jchkItalic);add(jpCheckBoxes, BorderLayout.EAST);/ Register listeners with the check boxesjchkCentered.addActionListener(new Actio
24、nListener() public void actionPerformed(ActionEvent e) messagePanel.setCentered(jchkCentered.isSelected(););jchkBold.addActionListener(new ActionListener() public void actionPerformed(ActionEvent e) setNewFont(););jchkItalic.addActionListener(new ActionListener() public void actionPerformed(ActionEv
25、ent e) setNewFont(););private void setNewFont() / Determine a font styleint fontStyle = Font.PLAIN;fontStyle += (jchkBold.isSelected() ? Font.BOLD : Font.PLAIN);fontStyle += (jchkItalic.isSelected() ? Font.ITALIC : Font.PLAIN);/ Set font for the messageFont font = messagePanel.getFont();messagePanel
26、.setFont(new Font(font.getName(), fontStyle, font.getSize(); ,Demo CheckBoxDemo .java,3 JRadioButton 单选按钮,Radio buttons are variations of check boxes. They are often used in the group, where only one button is checked at a time.,Grouping Radio Buttons 单选按钮组群,ButtonGroup btg = new ButtonGroup(); btg.
27、add(jrb1); btg.add(jrb2);,JRadioButton触发事件,当单选框被点击（选中或未选中）时，先触发一个ItemEvent,然后触发一个ActionEvent。要确定是否选中，用isSelected()方法，返回true表示被选中。 对于监听器的设置，可以选用ItemEvent 或者ActionEvent 两者之一。,Example: Using Radio Buttons,Add three radio buttons named Red, Green, and Blue into the preceding example to let the user choo
28、se the color of the message.,ButtonDemo,CheckBoxDemo,RadioButtonDemo,import java.awt.*; import java.awt.event.*; import javax.swing.*; public class RadioButtonDemo extends CheckBoxDemo / Declare radio buttonsprivate JRadioButton jrbRed, jrbGreen, jrbBlue;public static void main(String args) RadioBut
29、tonDemo frame = new RadioButtonDemo();frame.setLocationRelativeTo(null); / Center the frameframe.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);frame.setTitle(“RadioButtonDemo“);frame.setSize(500, 200);frame.setVisible(true);public RadioButtonDemo() / Create a new panel to hold check boxesJPanel jpR
30、adioButtons = new JPanel(); jpRadioButtons.setLayout(new GridLayout(3, 1);jpRadioButtons.add(jrbRed = new JRadioButton(“Red“);jpRadioButtons.add(jrbGreen = new JRadioButton(“Green“);jpRadioButtons.add(jrbBlue = new JRadioButton(“Blue“);add(jpRadioButtons, BorderLayout.WEST);/ Create a radio button g
31、roup to group three buttonsButtonGroup group = new ButtonGroup();group.add(jrbRed);group.add(jrbGreen);group.add(jrbBlue);/ Set keyboard mnemonicsjrbRed.setMnemonic(E); jrbGreen.setMnemonic(G);jrbBlue.setMnemonic(U);/ Register listeners for check boxesjrbRed.addActionListener(new ActionListener() pu
32、blic void actionPerformed(ActionEvent e) messagePanel.setForeground(Color.red););jrbGreen.addActionListener(new ActionListener() public void actionPerformed(ActionEvent e) messagePanel.setForeground(Color.green););jrbBlue.addActionListener(new ActionListener() public void actionPerformed(ActionEvent
33、 e) messagePanel.setForeground(Color.blue););/ Set initial message color to bluejrbBlue.setSelected(true);messagePanel.setForeground(Color.blue); ,Demo RadioButtonDemo .java,4 JLabel 标签,A label is a display area for a short text, an image, or both.,JLabel Constructors 构造方法,The constructors for label
34、s 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 Properties 属性,JLabel inherits all the properties from JComponent and has many proper
35、ties similar to the ones in JButton, such as text, icon, horizontalAlignment, verticalAlignment, horizontalTextPosition, verticalTextPosition.,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 h
36、orizontal alignment JLabel jlbl = new JLabel(“Grapes“, icon, SwingConstants.CENTER);/ Set labels text alignment and gap between text and icon jlbl.setHorizontalTextPosition(SwingConstants.CENTER); jlbl.setVerticalTextPosition(SwingConstants.BOTTOM); jlbl.setIconTextGap(5);,5 JTextField 文本域,A text fi
37、eld is an input area where the user can type in characters. Text fields are useful in that they enable the user to enter in variable data (such as a name or a description).,JTextField Constructors 构造方法,JTextField(int columns)Creates an empty text field with the specified number of columns. JTextFiel
38、d(String text)Creates a text field initialized with the specified text. JTextField(String text, int columns)Creates a text field initialized with the specified text and the column size.,JTextField Properties 常用属性,text horizontalAlignment editable columns,JTextField Methods 常用方法,getText()Returns the
39、string from the text field. setText(String text)Puts the given string in the text field. setEditable(boolean editable)Enables or disables the text field to be edited. By default, editable is true. setColumns(int)Sets the number of columns in this text field. The length of the text field is changeabl
40、e.,JTextField 触发事件,当光标移动到文本域，并且按回车键时，触发一个ActionEvent事件。,Example: Using Text Fields,Add a text field to the preceding example to let the user set a new message.,import java.awt.*; import java.awt.event.*; import javax.swing.*; public class TextFieldDemo extends RadioButtonDemo private JTextField jtfM
41、essage = new JTextField(10);/* Main method */public static void main(String args) TextFieldDemo frame = new TextFieldDemo();frame.pack();frame.setTitle(“TextFieldDemo“);frame.setLocationRelativeTo(null); / Center the frameframe.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);frame.setVisible(true);pu
42、blic TextFieldDemo() / Create a new panel to hold label and text fieldJPanel jpTextField = new JPanel();jpTextField.setLayout(new BorderLayout(5, 0); jpTextField.add(new JLabel(“Enter a new message“), BorderLayout.WEST);jpTextField.add(jtfMessage, BorderLayout.CENTER);add(jpTextField, BorderLayout.N
43、ORTH);jtfMessage.setHorizontalAlignment(JTextField.LEFT);/ Register listenerjtfMessage.addActionListener(new ActionListener() /* Handle ActionEvent */public void actionPerformed(ActionEvent e) messagePanel.setMessage(jtfMessage.getText();/ jtfMessage.requestFocusInWindow(); ); ,Demo TextFieldDemo .j
44、ava,6 JTextArea 文本区域,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 Constructors,JTextArea(int rows, int columns)Creates a text
45、 area with the specified number of rows and columns. JTextArea(String s, int rows, int columns)Creates a text area with the initial text and the number of rows and columns specified.,JTextArea Properties,text editable columns lineWrap wrapStyleWord rows lineCount tabSize,JTextArea Methods 常用方法,getTe
46、xt()Returns the string from the text field. setText(String text)Puts the given string in the text field. setEditable(boolean editable)Enables or disables the text field to be edited. By default, editable is true. setColumns(int)Sets the number of columns in this text field. The length of the text fi
47、eld is changeable.,JTextArea 触发事件,当光标移动到文本区域，并且按回车键时，触发一个ActionEvent事件。,Example: Using Text Areas,This example gives a program that displays an image in a label, a title in a label, and a text in a text area.,Example, cont.,JTextArea不处理滚动，但可以创建一个的对象，将JTextArea的实例放入其中，让JScrollPane为JTextArea处理滚动。JText
48、Area jtaDescription=new JTextArea (“dfdfd”); JScrollPane scrollPane = new JScrollPane(jtaDescription); add(scrollPane, BorderLayout.CENTER);,import java.awt.*; import javax.swing.*; public class TextAreaDemo extends JFrame / Declare and create a description panelprivate DescriptionPanel descriptionP
49、anel = new DescriptionPanel();public static void main(String args) TextAreaDemo frame = new TextAreaDemo();frame.pack();frame.setLocationRelativeTo(null);/ Center the frameframe.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);frame.setTitle(“TextAreaDemo“);frame.setVisible(true);public TextAreaDemo()
50、 / Set title, text and image in the description paneldescriptionPanel.setTitle(“Canada“);String description = “The Maple Leaf flag nn“ +“The Canadian National Flag was adopted by the Canadian “ +“Parliament on October 22, 1964 and was proclaimed into law “ +“by Her Majesty Queen Elizabeth II (the Qu
51、een of Canada) on “ +“February 15, 1965. The Canadian Flag (colloquially known “ +“as The Maple Leaf Flag) is a red flag of the proportions “ +“two by length and one by width, containing in its center a “ +“white square, with a single red stylized eleven-point “ +“mapleleaf centered in the white squ
52、are.“;descriptionPanel.setDescription(description);descriptionPanel.setImageIcon(new ImageIcon(“image/ca.gif“);/ Add the description panel to the framesetLayout(new BorderLayout();add(descriptionPanel, BorderLayout.CENTER); / Define a panel for displaying image and text class DescriptionPanel extend
53、s JPanel /* Label for displaying an image icon and a text */private JLabel jlblImageTitle = new JLabel();/* Text area for displaying text */private JTextArea jtaDescription = new JTextArea();public DescriptionPanel() / Center the icon and text and place the text under the iconjlblImageTitle.setHoriz
54、ontalAlignment(JLabel.CENTER);jlblImageTitle.setHorizontalTextPosition(JLabel.RIGHT);jlblImageTitle.setVerticalTextPosition(JLabel.BOTTOM);/ Set the font in the label and the text fieldjlblImageTitle.setFont(new Font(“SansSerif“, Font.BOLD, 16);jtaDescription.setFont(new Font(“Serif“, Font.PLAIN, 14
55、);/ Set lineWrap and wrapStyleWord true for the text areajtaDescription.setLineWrap(true);jtaDescription.setWrapStyleWord(true);jtaDescription.setEditable(false);/ Create a scroll pane to hold the text areaJScrollPane scrollPane = new JScrollPane(jtaDescription);/ Set BorderLayout for the panel, add
56、 label and scrollpanesetLayout(new BorderLayout(5, 5); add(scrollPane, BorderLayout.CENTER);add(jlblImageTitle, BorderLayout.WEST);/* Set the title */public void setTitle(String title) jlblImageTitle.setText(title);/* Set the image icon */public void setImageIcon(ImageIcon icon) jlblImageTitle.setIcon(icon);/* Set the text description */public void setDescription(String text) jtaDescription.setText(text); ,
