ThebaPrefs.java

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package theba.core.gui;

import java.awt.BorderLayout;
import java.awt.FlowLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.StringTokenizer;
import java.util.prefs.BackingStoreException;
import java.util.prefs.Preferences;

import javax.swing.JButton;
import javax.swing.JDialog;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JList;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextField;
import javax.swing.event.ListSelectionEvent;
import javax.swing.event.ListSelectionListener;

public class ThebaPrefs extends JDialog {
        private static final long serialVersionUID = 1L;

        private JTextField nameField = new JTextField(8);

        private JTextField valueField = new JTextField(8);

        private JList prefList = new JList(new String[] {});

        private Preferences prefs;

        private static ThebaPrefs instance;

        public static ThebaPrefs getInstance() {
                if (instance == null)
                        return new ThebaPrefs(null);
                return instance;
        }

        /*
         * Returns the current value for a given property or defaultValue if no
         * other value has been specified
         */
        public double getDouble(String name, double defaultValue) {
                double val = prefs.getDouble(name, defaultValue);
                if (val == defaultValue) {
                        prefs.putDouble(name, defaultValue);
                }
                return val;
        }

        public void setInt(String name, int value) {
                prefs.putInt(name, value);
        }

        public void setString(String name, String value) {
                if (value != null)
                        prefs.put(name, value);
        }

        public String getString(String name, String defaultValue) {
                String val = prefs.get(name, defaultValue);
                if (val == defaultValue && val != null) {
                        prefs.put(name, defaultValue);
                }
                return val;
        }

        public int getInt(String name, int defaultValue) {
                int val = prefs.getInt(name, defaultValue);
                if (val == defaultValue) {
                        prefs.putInt(name, defaultValue);
                }
                return val;
        }

        ThebaPrefs(JFrame f) {
                super(f);
                prefs = Preferences.userNodeForPackage(this.getClass());
                prefList.addListSelectionListener(new ListSelectionListener() {
                        public void valueChanged(ListSelectionEvent e) {
                                if (prefList.getSelectedValue() == null)
                                        return;
                                String value = prefList.getSelectedValue().toString();
                                StringTokenizer tk = new StringTokenizer(value, "=");
                                if (tk.hasMoreTokens())
                                        nameField.setText(tk.nextToken());
                                if (tk.hasMoreTokens())
                                        valueField.setText(tk.nextToken());
                        }
                });
                setTitle("Preferences");
                setModal(true);
                setListFromPrefs();
                // -- Create and set attributes of widgets.
                JScrollPane scrollingList = new JScrollPane(prefList);
                JButton newKeyButton = new JButton("Set value");
                JButton clearButton = new JButton("Clear All");
                JButton delSelectedButton = new JButton("Remove Selected");
                // -- Set action listeners.
                newKeyButton.addActionListener(new ActionListener() {
                        public void actionPerformed(ActionEvent e) {
                                if (nameField.getText().length() > 0) {
                                        prefs.put(nameField.getText(), valueField.getText());
                                        nameField.setText(""); // Clear fields after saving.
                                        valueField.setText("");
                                        setListFromPrefs(); // Update display
                                } else {
                                        nameField.setText("Key?");
                                }
                        }
                });
                clearButton.addActionListener(new ActionListener() {
                        public void actionPerformed(ActionEvent e) {
                                try {
                                        prefs.clear();
                                        setListFromPrefs(); // Update display
                                } catch (BackingStoreException ex) {
                                        System.out.println(ex);
                                }
                        }
                });
                delSelectedButton.addActionListener(new ActionListener() {
                        public void actionPerformed(ActionEvent e) {
                                String selection = (String) prefList.getSelectedValue();
                                if (selection != null) {
                                        String key = selection.substring(0, selection.indexOf("="));
                                        prefs.remove(key); // Remove the selected key.
                                        setListFromPrefs(); // Update display
                                }
                        }
                });
                // -- Layout widgets.
                JPanel buttonPanel = new JPanel(new FlowLayout());
                buttonPanel.add(new JLabel("Key"));
                buttonPanel.add(nameField);
                buttonPanel.add(new JLabel("Value"));
                buttonPanel.add(valueField);
                buttonPanel.add(newKeyButton);
                buttonPanel.add(delSelectedButton);
                buttonPanel.add(clearButton);
                JPanel content = new JPanel(new BorderLayout());
                content.add(buttonPanel, BorderLayout.NORTH);
                content.add(scrollingList, BorderLayout.CENTER);
                this.setContentPane(content);
                this.pack();
                setLocationRelativeTo(f);
        }

        private void setListFromPrefs() {
                try {
                        String[] keys = prefs.keys();
                        for (int i = 0; i < keys.length; i++) {
                                keys[i] += "=" + prefs.get(keys[i], "ERROR");
                        }
                        prefList.setListData(keys);
                } catch (BackingStoreException ex) {
                        System.out.println(ex);
                }
        }
}