TextSamplerDemo.java代码分析

/*
* TextSamplerDemo.java requires the following files:
* TextSamplerDemoHelp.html (which references images/dukeWaveRed.gif)
* images/Pig.gif
* images/sound.gif
*/

import javax.swing.*;
import javax.swing.text.*;

import java.awt.*; //for layout managers and more
import java.awt.event.*; //for action events

import java.net.URL;
import java.io.IOException;

public class TextSamplerDemo extends JPanel　// what is the difference between JPanel and JFrame?and why is JPanel,not JFrame here?????
implements ActionListener {
private String newline = "/n"; //what is newline?and what is it for???
protected static final String textFieldString = "JTextField";
protected static final String passwordFieldString = "JPasswordField";
protected static final String ftfString = "JFormattedTextField";
protected static final String buttonString = "JButton";

protected JLabel actionLabel;

public TextSamplerDemo() {
setLayout(new BorderLayout());

//Create a regular text field.
JTextField textField = new JTextField(10);
textField.setActionCommand(textFieldString);　　　//"setActionCommand"这是干什么的呢？？？找了半天也没找到它的描述！！！！如果没有这个方法会怎样呢？？？？？经试验，去掉后发现输入完成后再按Enter没反应了！！！！！！（终于找到了：JTextField has a method to establish the string used as the command string for the action event that gets fired. The java.awt.TextField used the text of the field as the command string for the ActionEvent. JTextField will use the command string set with the setActionCommand method if not null, otherwise it will use the text of the field as a compatibility with java.awt.TextField.那么再往深里分析呢？这个string是怎么的起作用呢？）
textField.addActionListener(this);

//Create a password field.
JPasswordField passwordField = new JPasswordField(10);
passwordField.setActionCommand(passwordFieldString);
passwordField.addActionListener(this);

//Create a formatted text field.
JFormattedTextField ftf = new JFormattedTextField(
java.util.Calendar.getInstance().getTime());
ftf.setActionCommand(textFieldString);
ftf.addActionListener(this);

//Create some labels for the fields.
JLabel textFieldLabel = new JLabel(textFieldString + ": ");
textFieldLabel.setLabelFor(textField);
JLabel passwordFieldLabel = new JLabel(passwordFieldString + ": ");
passwordFieldLabel.setLabelFor(passwordField);
JLabel ftfLabel = new JLabel(ftfString + ": ");
ftfLabel.setLabelFor(ftf);

//Create a label to put messages during an action event.
actionLabel = new JLabel("Type text and then Enter in a field.");
actionLabel.setBorder(BorderFactory.createEmptyBorder(10,0,0,0));

//Lay out the text controls and the labels.
JPanel textControlsPane = new JPanel();
GridBagLayout gridbag = new GridBagLayout();
GridBagConstraints c = new GridBagConstraints();　　//再细看GridBadConstraints()方法

textControlsPane.setLayout(gridbag);

JLabel[] labels = {textFieldLabel, passwordFieldLabel, ftfLabel}; //以这种Array有什么好处？？？？
JTextField[] textFields = {textField, passwordField, ftf};
addLabelTextRows(labels, textFields, gridbag, textControlsPane);

c.gridwidth = GridBagConstraints.REMAINDER; //last
c.anchor = GridBagConstraints.WEST;
c.weightx = 1.0;
textControlsPane.add(actionLabel, c);
textControlsPane.setBorder(
BorderFactory.createCompoundBorder(
BorderFactory.createTitledBorder("Text Fields"),
BorderFactory.createEmptyBorder(5,5,5,5)));

//Create a text area.
JTextArea textArea = new JTextArea(
"This is an editable JTextArea. " +
"A text area is a /"plain/" text component, " +
"which means that although it can display text " +
"in any font, all of the text is in the same font."
);
textArea.setFont(new Font("Serif", Font.ITALIC, 16));
textArea.setLineWrap(true);
textArea.setWrapStyleWord(true);
JScrollPane areaScrollPane = new JScrollPane(textArea);
areaScrollPane.setVerticalScrollBarPolicy(
JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);
areaScrollPane.setPreferredSize(new Dimension(250, 250));
areaScrollPane.setBorder(
BorderFactory.createCompoundBorder(
BorderFactory.createCompoundBorder(
BorderFactory.createTitledBorder("Plain Text"),
BorderFactory.createEmptyBorder(5,5,5,5)),
areaScrollPane.getBorder()));

//Create an editor pane.
JEditorPane editorPane = createEditorPane();
JScrollPane editorScrollPane = new JScrollPane(editorPane);
editorScrollPane.setVerticalScrollBarPolicy(
JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);
editorScrollPane.setPreferredSize(new Dimension(250, 145));
editorScrollPane.setMinimumSize(new Dimension(10, 10));

//Create a text pane.
JTextPane textPane = createTextPane();
JScrollPane paneScrollPane = new JScrollPane(textPane);
paneScrollPane.setVerticalScrollBarPolicy(
JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);
paneScrollPane.setPreferredSize(new Dimension(250, 155));
paneScrollPane.setMinimumSize(new Dimension(10, 10));

//Put the editor pane and the text pane in a split pane.
JSplitPane splitPane = new JSplitPane(JSplitPane.VERTICAL_SPLIT,
editorScrollPane,
paneScrollPane);
splitPane.setOneTouchExpandable(true);
splitPane.setResizeWeight(0.5);
JPanel rightPane = new JPanel(new GridLayout(1,0));
rightPane.add(splitPane);
rightPane.setBorder(BorderFactory.createCompoundBorder(
BorderFactory.createTitledBorder("Styled Text"),
BorderFactory.createEmptyBorder(5,5,5,5)));

//Put everything together.
JPanel leftPane = new JPanel(new BorderLayout());
leftPane.add(textControlsPane,
BorderLayout.PAGE_START);
leftPane.add(areaScrollPane,
BorderLayout.CENTER);

add(leftPane, BorderLayout.LINE_START);
add(rightPane, BorderLayout.LINE_END);
}

private void addLabelTextRows(JLabel[] labels,
JTextField[] textFields,
GridBagLayout gridbag,
Container container) {
GridBagConstraints c = new GridBagConstraints();
c.anchor = GridBagConstraints.EAST;
int numLabels = labels.length;

for (int i = 0; i < numLabels; i++) {
c.gridwidth = GridBagConstraints.RELATIVE; //next-to-last
c.fill = GridBagConstraints.NONE; //reset to default
c.weightx = 0.0; //reset to default
container.add(labels[i], c);

c.gridwidth = GridBagConstraints.REMAINDER; //end row
c.fill = GridBagConstraints.HORIZONTAL;
c.weightx = 1.0;
container.add(textFields[i], c);
}
}

public void actionPerformed(ActionEvent e) {
String prefix = "You typed /"";
if (textFieldString.equals(e.getActionCommand())) {
JTextField source = (JTextField)e.getSource();
actionLabel.setText(prefix + source.getText() + "/"");
} else if (passwordFieldString.equals(e.getActionCommand())) {
JPasswordField source = (JPasswordField)e.getSource();
actionLabel.setText(prefix + new String(source.getPassword())
+ "/"");
} else if (buttonString.equals(e.getActionCommand())) {
Toolkit.getDefaultToolkit().beep();
}
}

private JEditorPane createEditorPane() {
JEditorPane editorPane = new JEditorPane();
editorPane.setEditable(false);
java.net.URL helpURL = TextSamplerDemo.class.getResource(
"TextSamplerDemoHelp.html");
if (helpURL != null) {
try {
editorPane.setPage(helpURL);
} catch (IOException e) {
System.err.println("Attempted to read a bad URL: " + helpURL);
}
} else {
System.err.println("Couldn't find file: TextSampleDemoHelp.html");
}

return editorPane;
}

private JTextPane createTextPane() {
String[] initString =
{ "This is an editable JTextPane, ", //regular
"another ", //italic
"styled ", //bold
"text ", //small
"component, ", //large
"which supports embedded components..." + newline,//regular
" " + newline, //button
"...and embedded icons..." + newline, //regular
" ", //icon
newline + "JTextPane is a subclass of JEditorPane that " +
"uses a StyledEditorKit and StyledDocument, and provides " +
"cover methods for interacting with those objects."
};

String[] initStyles =
{ "regular", "italic", "bold", "small", "large",
"regular", "button", "regular", "icon",
"regular"
};

JTextPane textPane = new JTextPane();
StyledDocument doc = textPane.getStyledDocument();
addStylesToDocument(doc);

try {
for (int i=0; i < initString.length; i++) {
doc.insertString(doc.getLength(), initString[i],
doc.getStyle(initStyles[i]));
}
} catch (BadLocationException ble) {
System.err.println("Couldn't insert initial text into text pane.");
}

return textPane;
}

protected void addStylesToDocument(StyledDocument doc) {
//Initialize some styles.
Style def = StyleContext.getDefaultStyleContext().
getStyle(StyleContext.DEFAULT_STYLE);

Style regular = doc.addStyle("regular", def);
StyleConstants.setFontFamily(def, "SansSerif");

Style s = doc.addStyle("italic", regular);
StyleConstants.setItalic(s, true);

s = doc.addStyle("bold", regular);
StyleConstants.setBold(s, true);

s = doc.addStyle("small", regular);
StyleConstants.setFontSize(s, 10);

s = doc.addStyle("large", regular);
StyleConstants.setFontSize(s, 16);

s = doc.addStyle("icon", regular);
StyleConstants.setAlignment(s, StyleConstants.ALIGN_CENTER);
ImageIcon pigIcon = createImageIcon("images/Pig.gif",
"a cute pig");
if (pigIcon != null) {
StyleConstants.setIcon(s, pigIcon);
}

s = doc.addStyle("button", regular);
StyleConstants.setAlignment(s, StyleConstants.ALIGN_CENTER);
ImageIcon soundIcon = createImageIcon("images/sound.gif",
"sound icon");
JButton button = new JButton();
if (soundIcon != null) {
button.setIcon(soundIcon);
} else {
button.setText("BEEP");
}
button.setCursor(Cursor.getDefaultCursor());
button.setMargin(new Insets(0,0,0,0));
button.setActionCommand(buttonString);
button.addActionListener(this);
StyleConstants.setComponent(s, button);
}

/** Returns an ImageIcon, or null if the path was invalid. */
protected static ImageIcon createImageIcon(String path,
String description) {
java.net.URL imgURL = TextSamplerDemo.class.getResource(path);
if (imgURL != null) {
return new ImageIcon(imgURL, description);
} else {
System.err.println("Couldn't find file: " + path);
return null;
}
}

/**
* Create the GUI and show it. For thread safety,
* this method should be invoked from the
* event-dispatching thread.
*/
private static void createAndShowGUI() {
//Create and set up the window.
JFrame frame = new JFrame("TextSamplerDemo");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

//Create and set up the content pane.
JComponent newContentPane = new TextSamplerDemo();
newContentPane.setOpaque(true); //content panes must be opaque
frame.setContentPane(newContentPane);

//Display the window.
frame.pack();
frame.setVisible(true);
}

public static void main(String[] args) {
//Schedule a job for the event-dispatching thread:
//creating and showing this application's GUI.
javax.swing.SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGUI();
}
});
}
}