写在之前
以下是《Java8编程入门官方教程》中的一些知识，如有错误，烦请指正。涉及的程序如需下载请移步http://down1.tupwk.com.cn/qhwkdownpage/978-7-302-38738-1.zip
概念：Swing定义了一个类和接口的集合，支持丰富的可视化组件集，这些控件共同构建功能强大且易用的图形界面。
组件和容器
组件：是指独立的可视化控件；
容器可以包含一组组件。容器也是组件。
// A simple Swing program.
import javax.swing.*;
class SwingDemo {
SwingDemo() {
// Create a new JFrame container. 容器
JFrame jfrm = new JFrame("A Simple Swing Application");
// Give the frame an initial size.
jfrm.setSize(275, 100);
// Terminate the program when the user closes the application.
jfrm.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
// Create a text-based label.
JLabel jlab = new JLabel(" Swing defines the modern Java GUI.");
// Add the label to the content pane.
jfrm.add(jlab);
// Display the frame.
jfrm.setVisible(true);
}
public static void main(String args[]) {
// Create the frame on the event dispatching thread.
SwingUtilities.invokeLater(new Runnable() {
public void run() {
new SwingDemo();
}
});
}
}
JButton
listing 2
// Demonstrate a push button and handle action events.
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
class ButtonDemo implements ActionListener {
JLabel jlab;
ButtonDemo() {
// Create a new JFrame container.
JFrame jfrm = new JFrame("A Button Example");
// Specify FlowLayout for the layout manager.
jfrm.setLayout(new FlowLayout());
// Give the frame an initial size.
jfrm.setSize(220, 90);
// Terminate the program when the user closes the application.
jfrm.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
// Make two buttons.
JButton jbtnUp = new JButton("Up");
JButton jbtnDown = new JButton("Down");
// Add action listeners.
jbtnUp.addActionListener(this);
jbtnDown.addActionListener(this);
// Add the buttons to the content pane.
jfrm.add(jbtnUp);
jfrm.add(jbtnDown);
// Create a label.
jlab = new JLabel("Press a button.");
// Add the label to the frame.
jfrm.add(jlab);
// Display the frame.
jfrm.setVisible(true);
}
// Handle button events.
public void actionPerformed(ActionEvent ae) {
if(ae.getActionCommand().equals("Up"))
jlab.setText("You pressed Up.");
else
jlab.setText("You pressed down. ");
}
public static void main(String args[]) {
// Create the frame on the event dispatching thread.
SwingUtilities.invokeLater(new Runnable() {
public void run() {
new ButtonDemo();
}
});
}
}
JTextField
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
class TFDemo implements ActionListener {
JTextField jtf;
JButton jbtnRev;
JLabel jlabPrompt, jlabContents;
TFDemo() {
// Create a new JFrame container.
JFrame jfrm = new JFrame("Use a Text Field");
// Specify FlowLayout for the layout manager.
jfrm.setLayout(new FlowLayout());
// Give the frame an initial size.
jfrm.setSize(240, 120);
// Terminate the program when the user closes the application.
jfrm.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
// Create a text field.
jtf = new JTextField(10);
// Set the action commands for the text field.
jtf.setActionCommand("myTF");
// Create the Reverse button.
JButton jbtnRev = new JButton("Reverse");
// Add action listeners.
jtf.addActionListener(this);
jbtnRev.addActionListener(this);
// Create the labels.
jlabPrompt = new JLabel("Enter text: ");
jlabContents = new JLabel("");
// Add the components to the content pane.
jfrm.add(jlabPrompt);
jfrm.add(jtf);
jfrm.add(jbtnRev);
jfrm.add(jlabContents);
// Display the frame.
jfrm.setVisible(true);
}
// Handle action events.
public void actionPerformed(ActionEvent ae) {
if(ae.getActionCommand().equals("Reverse")) {
// The Reverse button was pressed.
String orgStr = jtf.getText();
String resStr = "";
// Reverse the string in the text field.
for(int i=orgStr.length()-1; i >=0; i--)
resStr += orgStr.charAt(i);
// Store the reversed string in the text field.
jtf.setText(resStr);
} else
// Enter was pressed while focus was in the
// text field.
jlabContents.setText("You pressed ENTER. Text is: " +
jtf.getText());
}
public static void main(String args[]) {
// Create the frame on the event dispatching thread.
SwingUtilities.invokeLater(new Runnable() {
public void run() {
new TFDemo();
}
});
}
}
JCheckBox
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
class CBDemo implements ItemListener {
JLabel jlabSelected;
JLabel jlabChanged;
JCheckBox jcbAlpha;
JCheckBox jcbBeta;
JCheckBox jcbGamma;
CBDemo() {
// Create a new JFrame container.
JFrame jfrm = new JFrame("Demonstrate Check Boxes");
// Specify FlowLayout for the layout manager.
jfrm.setLayout(new FlowLayout());
// Give the frame an initial size.
jfrm.setSize(280, 120);
// Terminate the program when the user closes the application.
jfrm.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
// Create empty labels.
jlabSelected = new JLabel("");
jlabChanged = new JLabel("");
// Make check boxes.
jcbAlpha = new JCheckBox("Alpha");
jcbBeta = new JCheckBox("Beta");
jcbGamma = new JCheckBox("Gamma");
// Events generated by the check boxes
// are handled in common by the itemStateChanged()
// method implemented by CBDemo.
jcbAlpha.addItemListener(this);
jcbBeta.addItemListener(this);
jcbGamma.addItemListener(this);
// Add checkboxes and labels to the content pane.
jfrm.add(jcbAlpha);
jfrm.add(jcbBeta);
jfrm.add(jcbGamma);
jfrm.add(jlabChanged);
jfrm.add(jlabSelected);
// Display the frame.
jfrm.setVisible(true);
}
// This is the handler for the check boxes.
public void itemStateChanged(ItemEvent ie) {
String str = "";
// Obtain a reference to the check box that
// caused the event.
JCheckBox cb = (JCheckBox) ie.getItem();
// Report what check box changed.
if(cb.isSelected())
jlabChanged.setText(cb.getText() + " was just selected.");
else
jlabChanged.setText(cb.getText() + " was just cleared.");
// Report all selected boxes.
if(jcbAlpha.isSelected()) {
str += "Alpha ";
}
if(jcbBeta.isSelected()) {
str += "Beta ";
}
if(jcbGamma.isSelected()) {
str += "Gamma";
}
jlabSelected.setText("Selected check boxes: " + str);
}
public static void main(String args[]) {
// Create the frame on the event dispatching thread.
SwingUtilities.invokeLater(new Runnable() {
public void run() {
new CBDemo();
}
});
}
}
Jlist
// Demonstrate a simple JList.
// This program requires JDK 7 or later.
import javax.swing.*;
import javax.swing.event.*;
import java.awt.*;
import java.awt.event.*;
class ListDemo implements ListSelectionListener {
JList<String> jlst;
JLabel jlab;
JScrollPane jscrlp;
// Create an array of names.
String names[] = { "Sherry", "Jon", "Rachel",
"Sasha", "Josselyn", "Randy",
"Tom", "Mary", "Ken",
"Andrew", "Matt", "Todd" };
ListDemo() {
// Create a new JFrame container.
JFrame jfrm = new JFrame("JList Demo");
// Specify a flow Layout.
jfrm.setLayout(new FlowLayout());
// Give the frame an initial size.
jfrm.setSize(200, 160);
// Terminate the program when the user closes the application.
jfrm.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
// Create a JList.
jlst = new JList<String>(names);
// Set the list selection mode to single-selection.
jlst.setSelectionMode(ListSelectionModel.SINGLE_SELECTION);
// Add list to a scroll pane.
jscrlp = new JScrollPane(jlst);
// Set the preferred size of the scroll pane.
jscrlp.setPreferredSize(new Dimension(120, 90));
// Make a label that displays the selection.
jlab = new JLabel("Please choose a name");
// Add list selection handler.
jlst.addListSelectionListener(this);
// Add the list and label to the content pane.
jfrm.add(jscrlp);
jfrm.add(jlab);
// Display the frame.
jfrm.setVisible(true);
}
// Handle list selection events.
public void valueChanged(ListSelectionEvent le) {
// Get the index of the changed item.
int idx = jlst.getSelectedIndex();
// Display selection, if item was selected.
if(idx != -1)
jlab.setText("Current selection: " + names[idx]);
else // Othewise, reprompt.
jlab.setText("Please choose an name");
}
public static void main(String args[]) {
// Create the frame on the event dispatching thread.
SwingUtilities.invokeLater(new Runnable() {
public void run() {
new ListDemo();
}
});
}
}
基于Swing的小程序
// Demonstrate a simple JList.
// This program requires JDK 7 or later.
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.io.*;
class SwingFC implements ActionListener {
JTextField jtfFirst; // holds the first file name
JTextField jtfSecond; // holds the second file name
JButton jbtnComp; // button to compare the files
JLabel jlabFirst, jlabSecond; // displays prompts
JLabel jlabResult; // displays results and error messages
SwingFC() {
// Create a new JFrame container.
JFrame jfrm = new JFrame("Compare Files");
// Specify FlowLayout for the layout manager.
jfrm.setLayout(new FlowLayout());
// Give the frame an initial size.
jfrm.setSize(200, 190);
// Terminate the program when the user closes the application.
jfrm.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
// Create the text fields for the file names..
jtfFirst = new JTextField(14);
jtfSecond = new JTextField(14);
// Set the action commands for the text fields.
jtfFirst.setActionCommand("fileA");
jtfSecond.setActionCommand("fileB");
// Create the Compare button.
JButton jbtnComp = new JButton("Compare");
// Add action listener for the Compare button.
jbtnComp.addActionListener(this);
// Create the labels.
jlabFirst = new JLabel("First file: ");
jlabSecond = new JLabel("Second file: ");
jlabResult = new JLabel("");
// Add the components to the content pane.
jfrm.add(jlabFirst);
jfrm.add(jtfFirst);
jfrm.add(jlabSecond);
jfrm.add(jtfSecond);
jfrm.add(jbtnComp);
jfrm.add(jlabResult);
// Display the frame.
jfrm.setVisible(true);
}
// Compare the files when the Compare button is pressed.
public void actionPerformed(ActionEvent ae) {
int i=0, j=0;
// First, confirm that both file names have
// been entered.
if(jtfFirst.getText().equals("")) {
jlabResult.setText("First file name missing.");
return;
}
if(jtfSecond.getText().equals("")) {
jlabResult.setText("Second file name missing.");
return;
}
// Compare files. Use try-with-resources to manage the files.
try (FileInputStream f1 = new FileInputStream(jtfFirst.getText());
FileInputStream f2 = new FileInputStream(jtfSecond.getText()))
{
// Check the contents of each file.
do {
i = f1.read();
j = f2.read();
if(i != j) break;
} while(i != -1 && j != -1);
if(i != j)
jlabResult.setText("Files are not the same.");
else
jlabResult.setText("Files compare equal.");
} catch(IOException exc) {
jlabResult.setText("File Error");
}
}
public static void main(String args[]) {
// Create the frame on the event dispatching thread.
SwingUtilities.invokeLater(new Runnable() {
public void run() {
new SwingFC();
}
});
}
}
使用匿名内部类或者lambda表达式处理事件
匿名内部类是没有名称的内部类，该类的实例只是在需要时即时生成
jbtn.addActionListener(new ActionListener{
public void actionPerformed(ActionEvent ae){
// handle action event here
}
});
通过lambda表达式可以更加简洁
jbtn.addActionListener((ae) -> {
//handle action event here
}
);
Swing applet
基于Swing的applet扩展了JApplet而不是Applet。JApplet派生自Applet，因此包含后者所有功能，并且支持Swing。类似基于AWT的applet。
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
/*
This HTML can be used to launch the applet:
<applet code="MySwingApplet" width=200 height=80>
</applet>
*/
public class MySwingApplet extends JApplet {
JButton jbtnUp;
JButton jbtnDown;
JLabel jlab;
// Initialize the applet.
public void init() {
try {
SwingUtilities.invokeAndWait(new Runnable () {
public void run() {
makeGUI(); // initialize the GUI
}
});
} catch(Exception exc) {
System.out.println("Can't create because of "+ exc);
}
}
// This applet does not need to override start(), stop(),
// or destroy().
// Setup and initialize the GUI.
private void makeGUI() {
// Set the applet to use flow layout.
setLayout(new FlowLayout());
// Make two buttons.
jbtnUp = new JButton("Up");
jbtnDown = new JButton("Down");
// Add action listener for Up button..
jbtnUp.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent ae) {
jlab.setText("You pressed Up.");
}
});
// Add action listener for Down button.
jbtnDown.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent ae) {
jlab.setText("You pressed down.");
}
});
// Add the buttons to the content pane.
add(jbtnUp);
add(jbtnDown);
// Create a text-based label.
jlab = new JLabel("Press a button.");
// Add the label to the content pane.
add(jlab);
}
}
