Using preferences

The Preferences API is not part of Swing, but is often used in graphical applications. It provides a lightweight and simple way of storing application and user preferences, without directly accessing the file system or using JNDI.

Example

Here, the Preferences API is used to store and access user preferences related to the general look and feel of an application:

Note the field fPrefs, and the pairs of keys and default values for each preference.

package hirondelle.stocks.preferences;

import java.util.*;
import java.util.logging.*;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.util.prefs.*;
import javax.swing.plaf.metal.MetalTheme;

import hirondelle.stocks.util.ui.Theme;
import hirondelle.stocks.util.ui.UiConsts;
import hirondelle.stocks.util.ui.UiUtil;
import hirondelle.stocks.util.Util;

/**
* Allows editing of user preferences related to the general 
* appearance of the application, such as font size, toolbar icon size, theme, 
* and the like.
*
* <P>Also allows programmatic read-only access to the current stored preferences 
* for these items.
*/
public final class GeneralLookPreferencesEditor extends Observable 
  implements PreferencesEditor {

  @Override public JComponent getUI(){
    JPanel content = new JPanel();
    GridBagLayout gridbag = new GridBagLayout();
    content.setLayout(gridbag);
    addShowToolbarAndLargeIcons(content);
    addTheme(content);
    addRestoreDefaults(content);
    UiUtil.addVerticalGridGlue(content, 4);
    matchGuiToStoredPrefs();
    return content;
  }
  
  @Override public String getTitle() {
    return TITLE;
  }
  
  @Override public int getMnemonic() {
    return MNEMONIC;
  }

  @Override public void savePreferences(){
    fLogger.fine("Updating general preferences.");
    fPrefs.putBoolean(SHOW_TOOL_BAR_KEY, fShowToolBar.isSelected());
    fPrefs.putBoolean(USE_LARGE_ICONS, fLargeIcons.isSelected());
    fPrefs.put(THEME_NAME_KEY, fThemes.getSelectedItem().toString());
    setChanged();
    notifyObservers();
  }

  @Override public void matchGuiToDefaultPreferences(){
    fShowToolBar.setSelected(SHOW_TOOLBAR_DEFAULT);
    fLargeIcons.setSelected(USE_LARGE_ICONS_DEFAULT);
    fThemes.setSelectedItem(Theme.valueOf(THEME_NAME_DEFAULT));
  }

  /**
  * Return the stored user preference for hiding or showing the toolbar.
  */
  public boolean hasShowToolBar(){
    return fPrefs.getBoolean(SHOW_TOOL_BAR_KEY, SHOW_TOOLBAR_DEFAULT);
  }
  
  /**
  * Return the stored user preference for using large icons.
  */
  public boolean hasLargeIcons(){
    return fPrefs.getBoolean(USE_LARGE_ICONS, USE_LARGE_ICONS_DEFAULT);
  }
  
  /**
  * Return the stored user preference for the theme to be applied to the Java 
  * look-and-feel.
  */
  public MetalTheme getTheme(){
    String themeName = fPrefs.get(THEME_NAME_KEY, THEME_NAME_DEFAULT);
    return Theme.valueOf(themeName);
  }
  
  // PRIVATE

  private static final String GENERAL_LOOK_NODE = "stocksmonitor/ui/prefs/GeneralLook";
  private Preferences fPrefs = Preferences.userRoot().node(GENERAL_LOOK_NODE);

  private static final String TITLE = "General Look";
  private static final int MNEMONIC = KeyEvent.VK_G;
  
  private static final boolean SHOW_TOOLBAR_DEFAULT = true;
  private static final String SHOW_TOOL_BAR_KEY = "ShowToolbar";

  private static final boolean USE_LARGE_ICONS_DEFAULT = false;
  private static final String USE_LARGE_ICONS = "UseLargeIcons";

  //Theme name is mapped to Theme using Theme.valueOf
  private static final String THEME_NAME_DEFAULT = "Default";
  private static final String THEME_NAME_KEY = "ThemeName";

  private JCheckBox fShowToolBar;
  private JCheckBox fLargeIcons;
  private JComboBox<MetalTheme> fThemes;
  
  private static final Logger fLogger = Util.getLogger(GeneralLookPreferencesEditor.class);
  
  private void matchGuiToStoredPrefs(){
    fShowToolBar.setSelected(hasShowToolBar());
    fLargeIcons.setSelected(hasLargeIcons());
    fThemes.setSelectedItem(getTheme());
  }
  
  private void addShowToolbarAndLargeIcons(JPanel aContent){
    JLabel toolbar = new JLabel("Show:");
    aContent.add(toolbar, getConstraints(0,0));
    
    fShowToolBar = new JCheckBox("Toolbar");
    fShowToolBar.setMnemonic(KeyEvent.VK_O);
    aContent.add(fShowToolBar, getConstraints(0,1));
    
    JLabel iconSize = new JLabel("Icon Size:");
    aContent.add(iconSize, getConstraints(1,0));

    fLargeIcons = new JCheckBox("Use Large Icons");
    fLargeIcons.setMnemonic(KeyEvent.VK_U);
    iconSize.setLabelFor(fLargeIcons);
    aContent.add(fLargeIcons, getConstraints(1,1));
  }

  private void addTheme(JPanel aContent) {
    JLabel theme = new JLabel("Theme:");
    theme.setDisplayedMnemonic(KeyEvent.VK_T);
    aContent.add(theme, getConstraints(2,0));
    
    DefaultComboBoxModel<MetalTheme> themesModel = new DefaultComboBoxModel<MetalTheme>(
      Theme.VALUES.toArray(new MetalTheme[0])
    );
    fThemes = new JComboBox<MetalTheme>(themesModel);
    theme.setLabelFor(fThemes);
    aContent.add(fThemes, getConstraints(2,1));
  }

  private void addRestoreDefaults(JPanel aContent) {
    JButton restore = new JButton("Restore Defaults");
    restore.setMnemonic(KeyEvent.VK_D);
    restore.addActionListener( new ActionListener() {
      @Override public void actionPerformed(ActionEvent event) {
        matchGuiToDefaultPreferences();
      }
    });
    GridBagConstraints constraints = UiUtil.getConstraints(3,1);
    constraints.insets = new Insets(UiConsts.ONE_SPACE, 0,0,0);
    aContent.add( restore, constraints );
  }
  
  private GridBagConstraints getConstraints(int aY, int aX){
    GridBagConstraints result = UiUtil.getConstraints(aY, aX);
    result.insets = new Insets(0, 0, UiConsts.ONE_SPACE, UiConsts.ONE_SPACE);
    return result;
  }
}
 



See Also :
Preferences dialogs
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