Undo the effect of method setText() of JEditorPane in one step not in three

Question

I'm trying to undo the setText() method effect in a JEditorPane. Here is my code:

public final class UndoManagerTestForJEditorPane {

private final JEditorPane editor = new JEditorPane();
private final UndoManager undoManager = new UndoManager();

public JComponent makeUI() {
    editor.setContentType("text/html");
    HTMLDocument document = (HTMLDocument) editor.getDocument();
    document.addUndoableEditListener(undoManager);
    editor.setText("Hello");

    JPanel p = new JPanel();
    p.add(new JButton(new AbstractAction("undo") {
        @Override
        public void actionPerformed(ActionEvent e) {
            if (undoManager.canUndo()) {
                undoManager.undo();
            }
        }
    }));
    p.add(new JButton(new AbstractAction("redo") {
        @Override
        public void actionPerformed(ActionEvent e) {
            if (undoManager.canRedo()) {
                undoManager.redo();
            }
        }
    }));
    p.add(new JButton(new AbstractAction("setText(new Date())") {
        @Override
        public void actionPerformed(ActionEvent e) {
            String str = new Date().toString();
            editor.setText(str);
        }
    }));

    Box box = Box.createVerticalBox();
    box.setBorder(BorderFactory.createEmptyBorder(5, 5, 5, 5));
    box.add(makePanel("Default", editor));

    JPanel pp = new JPanel(new BorderLayout());
    pp.add(box, BorderLayout.NORTH);
    pp.add(p, BorderLayout.SOUTH);
    return pp;
}

private static JPanel makePanel(String title, JComponent c) {
    JPanel p = new JPanel(new BorderLayout());
    p.setBorder(BorderFactory.createTitledBorder(title));
    p.add(c);
    return p;
}

public static void main(String[] args) {
    EventQueue.invokeLater(new Runnable() {
        @Override
        public void run() {
            createAndShowGUI();
        }
    });
}

public static void createAndShowGUI() {
    JFrame f = new JFrame();
    f.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
    f.getContentPane().add(new UndoManagerTestForJEditorPane().makeUI());
    f.setSize(320, 240);
    f.setLocationRelativeTo(null);
    f.setVisible(true);
}
}

The default behaviour is done with four steps:

1) Nothing is done, the cursor doesn't even move..

2) The cursor gets down with almost 10 lines under the inserted word..

3) The text get disappeared..

4) the old text appears finally..

So, instead of these steps, could we do it just only with one undo step like in this link for JTextField JTextArea setText() & UndoManager, but with JEditorPane ?

The problem the replace method for JEditorPane does not get executed when setText() is called on JEditorPane...

Please any help ?

Thank you

Answer 1

You could do it with a separate class (can be nested to directly access the necessary GUI elements, if you only have to do your edits with informations from one class) which extends AbstractUndoableEdit. You can save the exact old state that you want to load after one undo operation and the exact new state which you want to reload after a redo operation. You can then set the correct values in the redo and undo methods directly by overriding them in the State class. This could look like this:

public final class UndoManagerTestForJEditorPane {

private final JEditorPane editor = new JEditorPane();
private final UndoManager undoManager = new UndoManager();

public JComponent makeUI() {
    editor.setContentType("text/html");
    HTMLDocument document = (HTMLDocument) editor.getDocument();
    //document.addUndoableEditListener(undoManager);  -> Not used anymore
    editor.setText("Hello");

    JPanel p = new JPanel();
    p.add(new JButton(new AbstractAction("undo") {
        @Override
        public void actionPerformed(ActionEvent e) {
            if (undoManager.canUndo()) {
                undoManager.undo();
            }
        }
    }));

    // New class to hold the state and load the correct string
    class State extends AbstractUndoableEdit
    {
        String oldText;
        String newText;

        State(String oldText, String newText)
        {
            this.oldText = oldText;
            this.newText = newText;
        }

        @Override
        public void undo() throws CannotUndoException {
            editor.setText(oldText);
        }

        @Override
        public boolean canUndo() {
            return true;
        }

        @Override
        public void redo() throws CannotRedoException {
            editor.setText(newText);
        }

        @Override
        public boolean canRedo() {
            return true;
        }


    }
    p.add(new JButton(new AbstractAction("redo") {
        @Override
        public void actionPerformed(ActionEvent e) {
            if (undoManager.canRedo()) {
                undoManager.redo();
            }
        }
    }));
    p.add(new JButton(new AbstractAction("setText(new Date())") {
        @Override
        public void actionPerformed(ActionEvent e) {
            String str = new Date().toString();
            // Add a new edit by saving the old string (by calling getText) and the new string 'str'
            undoManager.addEdit(new State(editor.getText(), str));
            editor.setText(str);
        }
    }));



    Box box = Box.createVerticalBox();
    box.setBorder(BorderFactory.createEmptyBorder(5, 5, 5, 5));
    box.add(makePanel("Default", editor));

    JPanel pp = new JPanel(new BorderLayout());
    pp.add(box, BorderLayout.NORTH);
    pp.add(p, BorderLayout.SOUTH);
    return pp;
}

private static JPanel makePanel(String title, JComponent c) {
    JPanel p = new JPanel(new BorderLayout());
    p.setBorder(BorderFactory.createTitledBorder(title));
    p.add(c);
    return p;
}

public static void main(String[] args) {
    EventQueue.invokeLater(new Runnable() {
        @Override
        public void run() {
            createAndShowGUI();
        }
    });
}

public static void createAndShowGUI() {
    JFrame f = new JFrame();
    f.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
    f.getContentPane().add(new UndoManagerTestForJEditorPane().makeUI());
    f.setSize(320, 240);
    f.setLocationRelativeTo(null);
    f.setVisible(true);
}
}