UndoableToggleApp4.java Source code

Introduction

Here is the source code for UndoableToggleApp4.java

Source

import java.awt.BorderLayout;
import java.awt.Container;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.Hashtable;

import javax.swing.Box;
import javax.swing.BoxLayout;
import javax.swing.JButton;
import javax.swing.JCheckBox;
import javax.swing.JFrame;
import javax.swing.JRadioButton;
import javax.swing.JToggleButton;
import javax.swing.undo.CannotRedoException;
import javax.swing.undo.CannotUndoException;
import javax.swing.undo.StateEdit;
import javax.swing.undo.StateEditable;

public class UndoableToggleApp4 extends JFrame implements StateEditable {

    private JToggleButton tog = new JToggleButton("ToggleButton");

    private JCheckBox cb = new JCheckBox("CheckBox");

    private JRadioButton radio = new JRadioButton("RadioButton");

    private JButton undoButton = new JButton("Undo");

    private JButton redoButton = new JButton("Redo");

    private JButton startButton = new JButton("Start");

    private JButton endButton = new JButton("End");

    private StateEdit edit;

    public UndoableToggleApp4() {
        SimpleListener sl = new SimpleListener();
        tog.addActionListener(sl);
        cb.addActionListener(sl);
        radio.addActionListener(sl);

        Box buttonBox = new Box(BoxLayout.Y_AXIS);
        buttonBox.add(tog);
        buttonBox.add(cb);
        buttonBox.add(radio);

        startButton.setEnabled(true);
        endButton.setEnabled(false);
        undoButton.setEnabled(false);
        redoButton.setEnabled(false);

        startButton.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent ev) {
                edit = new StateEdit(UndoableToggleApp4.this);
                startButton.setEnabled(false);
                endButton.setEnabled(true);
                // undoButton.setEnabled(edit.canUndo());
                //
                // NOTE: We really don't want to be able to undo until end() is pressed,
                // but StateEdit does not enforce this for us!
                undoButton.setEnabled(false);
                redoButton.setEnabled(edit.canRedo());
            }
        });

        endButton.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent ev) {
                edit.end();
                startButton.setEnabled(true);
                endButton.setEnabled(false);
                undoButton.setEnabled(edit.canUndo());
                redoButton.setEnabled(edit.canRedo());
            }
        });

        // Add a listener to the undo button. It attempts to call undo() on the
        // current edit, then enables/disables the undo/redo buttons as appropriate.
        undoButton.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent ev) {
                try {
                    edit.undo();
                } catch (CannotUndoException ex) {
                    ex.printStackTrace();
                } finally {
                    undoButton.setEnabled(edit.canUndo());
                    redoButton.setEnabled(edit.canRedo());
                }
            }
        });

        redoButton.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent ev) {
                try {
                    edit.redo();
                } catch (CannotRedoException ex) {
                    ex.printStackTrace();
                } finally {
                    undoButton.setEnabled(edit.canUndo());
                    redoButton.setEnabled(edit.canRedo());
                }
            }
        });

        // Lay out the state/end and undo/redo buttons.
        Box undoRedoBox = new Box(BoxLayout.X_AXIS);
        undoRedoBox.add(Box.createGlue());
        undoRedoBox.add(startButton);
        undoRedoBox.add(Box.createHorizontalStrut(2));
        undoRedoBox.add(endButton);
        undoRedoBox.add(Box.createHorizontalStrut(2));
        undoRedoBox.add(undoButton);
        undoRedoBox.add(Box.createHorizontalStrut(2));
        undoRedoBox.add(redoButton);
        undoRedoBox.add(Box.createGlue());

        // Lay out the main frame.
        Container content = getContentPane();
        content.setLayout(new BorderLayout());
        content.add(buttonBox, BorderLayout.CENTER);
        content.add(undoRedoBox, BorderLayout.SOUTH);
        setSize(400, 150);
    }

    public class SimpleListener implements ActionListener {
        // When any toggle button is clicked, we turn off the undo and redo
        // buttons, reflecting the fact that we can only undo/redo the last
        // set of state changes as long as no additional changes have been made.
        public void actionPerformed(ActionEvent ev) {
            undoButton.setEnabled(false);
            redoButton.setEnabled(false);
        }
    }

    // Save the state of the app by storing the current state of the three
    // buttons. We'll use the buttons themselves as keys and their selected
    // state as values.
    public void storeState(Hashtable ht) {
        ht.put(tog, new Boolean(tog.isSelected()));
        ht.put(cb, new Boolean(cb.isSelected()));
        ht.put(radio, new Boolean(radio.isSelected()));
    }

    // Restore state based on the values we saved when storeState() was called.
    // Note that StateEdit discards any state info that did not change from
    // between the start state and the end state, so we can't assume that the
    // state for all 3 buttons is in the Hashtable.
    public void restoreState(Hashtable ht) {
        Boolean b1 = (Boolean) ht.get(tog);
        if (b1 != null)
            tog.setSelected(b1.booleanValue());
        Boolean b2 = (Boolean) ht.get(cb);
        if (b2 != null)
            cb.setSelected(b2.booleanValue());
        Boolean b3 = (Boolean) ht.get(radio);
        if (b3 != null)
            radio.setSelected(b3.booleanValue());
    }

    // Main program just creates the frame and displays it.
    public static void main(String[] args) {
        JFrame f = new UndoableToggleApp4();
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.setVisible(true);
    }
}