所以我一直有关于外观和感觉的问题。我有一个子菜单可以改变外观和感觉，但它没有做任何事情，它只调整窗口栏的大小。
1）我的代码存在的问题是，即使更新UI
，外观也不起作用2）当我改变外观时，由于某种原因，文本区域会改变大小。
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
public class NoteTaker extends JFrame
{
// Constants for set up of the note taking area
public static final int WIDTH = 600;
public static final int HEIGHT = 300;
public static final int LINES = 13;
public static final int CHAR_PER_LINE = 45;
// Objects in GUI
private JTextArea theText; // Text area to take notes
private JMenuBar mBar; // Horizontal menu bar
private JPanel textPanel; // Scrolling text area panel
private JMenu notesMenu; // Vertical menu for notes
// THESE ITEMS ARE NOT YET USED
// YOU WILL BE CREATING THEM IN THIS LAB
private JMenu viewMenu; // Vertical menu for views
private JMenu lafMenu; // Vertical menu look and feel
private JMenu sbMenu; // Vertical menu for scroll bar
private JScrollPane scrolledText; // Scroll bars
// Default notes
private String note1 = "No Note 1.";
private String note2 = "No Note 2.";
/**
Constructor
*/
public NoteTaker()
{
// Create a closeable JFrame with a specific size
super("Note Taker");
setSize(WIDTH, HEIGHT);
setDefaultCloseOperation (JFrame.EXIT_ON_CLOSE);
// Get contentPane and set layout of the window
Container contentPane = getContentPane();
contentPane.setLayout(new BorderLayout());
// Creates the vertical menus
createNotes();
createViews();
// Creates horizontal menu bar and
// adds vertical menus to it
mBar = new JMenuBar();
mBar.add(notesMenu);
mBar.add(viewMenu);
// ADD THE viewMenu TO THE MENU BAR HERE
setJMenuBar(mBar);
// Creates a panel to take notes on
textPanel = new JPanel();
textPanel.setBackground(Color.blue);
theText = new JTextArea(LINES, CHAR_PER_LINE);
theText.setBackground(Color.white);
// CREATE A JScrollPane OBJECT HERE CALLED
// scrolledText AND PASS IN theText, THEN
scrolledText = new JScrollPane(theText);
// CHANGE THE LINE BELOW BY PASSING IN scrolledText
textPanel.add(scrolledText);
contentPane.add(textPanel, BorderLayout.CENTER);
}
/**
Creates vertical menu associated with Notes
menu item on menu bar.
*/
public void createNotes()
{
notesMenu = new JMenu("Notes");
JMenuItem item;
item = new JMenuItem("Save Note 1");
item.addActionListener(new MenuListener());
notesMenu.add(item);
item = new JMenuItem("Save Note 2");
item.addActionListener(new MenuListener());
notesMenu.add(item);
item = new JMenuItem("Open Note 1");
item.addActionListener(new MenuListener());
notesMenu.add(item);
item = new JMenuItem("Open Note 2");
item.addActionListener(new MenuListener());
notesMenu.add(item);
item = new JMenuItem("Clear");
item.addActionListener(new MenuListener());
notesMenu.add(item);
item = new JMenuItem("Exit");
item.addActionListener(new MenuListener());
notesMenu.add(item);
}
/**
Creates vertical menu associated with Views
menu item on the menu bar.
*/
public void createViews()
{
viewMenu = new JMenu("Views"); // Creates Menu Item called Views on horizontal Menu Bar
createLookAndFeel(); //Creates submenu Look And Feel
lafMenu.addActionListener(new MenuListener());
createScrollBars(); //Creates submenu Scroll Bars
sbMenu.addActionListener(new MenuListener());
}
/**
Creates the look and feel Sub menu.
*/
public void createLookAndFeel()
{
lafMenu = new JMenu("Look and Feel"); //Creates Menu Item called Look and Feel
viewMenu.add(lafMenu);
//Adds Menu item metal
JMenuItem itemMetal;
itemMetal = new JMenuItem("Metal");
itemMetal.addActionListener(new MenuListener());
lafMenu.add(itemMetal);
//Adds Menu item Motif
JMenuItem itemMotif;
itemMotif = new JMenuItem("Motif");
itemMotif.addActionListener(new MenuListener());
lafMenu.add(itemMotif);
//Adds Menu item Windows
JMenuItem itemWindows;
itemWindows = new JMenuItem("Windows");
itemWindows.addActionListener(new MenuListener());
lafMenu.add(itemWindows);
}
/**
Creates the scroll bars submenu.
*/
public void createScrollBars()
{
sbMenu = new JMenu("Scroll Bars");
viewMenu.add(sbMenu);
//Adds MenuItem called Never
JMenuItem itemNever;
itemNever = new JMenuItem("Never");
itemNever.addActionListener(new MenuListener());
sbMenu.add(itemNever);
//Adds Menu item Always
JMenuItem itemAlways;
itemAlways = new JMenuItem("Always");
itemAlways.addActionListener(new MenuListener());
sbMenu.add(itemAlways);
//Adds Menu item As Needed
JMenuItem itemAsNeeded;
itemAsNeeded = new JMenuItem("As Needed");
itemAsNeeded.addActionListener(new MenuListener());
sbMenu.add(itemAsNeeded);
}
/**
Private inner class that handles the Menu object's
action events.
*/
private class MenuListener implements ActionListener
{
public void actionPerformed(ActionEvent e)
{
String actionCommand = e.getActionCommand();
if (actionCommand.equals("Save Note 1"))
note1 = theText.getText();
else if (actionCommand.equals("Save Note 2"))
note2 = theText.getText();
else if (actionCommand.equals("Clear"))
theText.setText("");
else if (actionCommand.equals("Open Note 1"))
theText.setText(note1);
else if (actionCommand.equals("Open Note 2"))
theText.setText(note2);
else if (actionCommand.equals("Exit"))
System.exit(0);
// ADD 6 BRANCHES TO THE ELSE-IF STRUCTURE
// TO ALLOW ACTION TO BE PERFORMED FOR EACH
// MENU ITEM YOU HAVE CREATED
else if (actionCommand.equals("Metal")) {
try {
UIManager.setLookAndFeel("javax.swing.plaf.metal.MetalLookAndFeel");
SwingUtilities.updateComponentTreeUI(getContentPane());
} catch (Exception e1) {
JOptionPane.showMessageDialog(null, "Error for Look and Feel");
System.exit(0);
}
} else if (actionCommand.equals("Motif")) {
try {
UIManager.setLookAndFeel("com.sun.java.swing.plaf.motif.MotifLookAndFeel");
SwingUtilities.updateComponentTreeUI(getContentPane());
} catch (Exception e1) {
JOptionPane.showMessageDialog(null, "Error setting the look and feel.");
System.exit(0);
}
} else if (actionCommand.equals("Windows")) {
try {
UIManager.setLookAndFeel("com.sun.java.swing.plaf.windows.WindowsLookAndFeel");
SwingUtilities.updateComponentTreeUI(getContentPane());
} catch (Exception e1) {
JOptionPane.showMessageDialog(null, "Error setting the look and feel.");
System.exit(0);
}
} else if (actionCommand.equals("Never")) {
scrolledText.setHorizontalScrollBarPolicy(JScrollPane.HORIZONTAL_SCROLLBAR_NEVER);
SwingUtilities.updateComponentTreeUI(getContentPane());
scrolledText.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_NEVER);
SwingUtilities.updateComponentTreeUI(getContentPane());
} else if (actionCommand.equals("Always")) {
scrolledText.setHorizontalScrollBarPolicy(JScrollPane.HORIZONTAL_SCROLLBAR_ALWAYS);
SwingUtilities.updateComponentTreeUI(getContentPane());
scrolledText.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);
SwingUtilities.updateComponentTreeUI(getContentPane());
} else if (actionCommand.equals("As Needed")) {
scrolledText.setHorizontalScrollBarPolicy(JScrollPane.HORIZONTAL_SCROLLBAR_AS_NEEDED);
SwingUtilities.updateComponentTreeUI(getContentPane());
scrolledText.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_AS_NEEDED);
SwingUtilities.updateComponentTreeUI(getContentPane());
}
else {
theText.setText("Error in memo interface");
}
}
}
/**
The main method creates an instance of the
NoteTaker class which causes it to display
its window.
*/
public static void main(String[] args)
{
NoteTaker gui = new NoteTaker();
gui.setVisible(true);
}
}
答案 0 :(得分：2)
问题在于，在更新组件树UI时，您不会更新菜单所在的部分。也就是说，菜单栏及其子组件do not位于内容窗格中。这可以通过简单地使用框架作为要更新的树的根来解决。如此改变
SwingUtilities.updateComponentTreeUI(getContentPane());
到
SwingUtilities.updateComponentTreeUI(NoteTaker.this);
应解决问题。