UndoManagerHelper.java Source code

Introduction

Here is the source code for UndoManagerHelper.java

Source

import java.awt.BorderLayout;
import java.awt.Component;
import java.awt.event.ActionEvent;

import javax.swing.AbstractAction;
import javax.swing.Action;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JOptionPane;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.JToolBar;
import javax.swing.UIManager;
import javax.swing.undo.CannotRedoException;
import javax.swing.undo.CannotUndoException;
import javax.swing.undo.UndoManager;

class UndoManagerHelper {

    public static Action getUndoAction(UndoManager manager, String label) {
        return new UndoAction(manager, label);
    }

    public static Action getUndoAction(UndoManager manager) {
        return new UndoAction(manager, (String) UIManager.get("AbstractUndoableEdit.undoText"));
    }

    public static Action getRedoAction(UndoManager manager, String label) {
        return new RedoAction(manager, label);
    }

    public static Action getRedoAction(UndoManager manager) {
        return new RedoAction(manager, (String) UIManager.get("AbstractUndoableEdit.redoText"));
    }

    private abstract static class UndoRedoAction extends AbstractAction {
        UndoManager undoManager = new UndoManager();

        String errorMessage = "Cannot undo";

        String errorTitle = "Undo Problem";

        protected UndoRedoAction(UndoManager manager, String name) {
            super(name);
            undoManager = manager;
        }

        public void setErrorMessage(String newValue) {
            errorMessage = newValue;
        }

        public void setErrorTitle(String newValue) {
            errorTitle = newValue;
        }

        protected void showMessage(Object source) {
            if (source instanceof Component) {
                JOptionPane.showMessageDialog((Component) source, errorMessage, errorTitle,
                        JOptionPane.WARNING_MESSAGE);
            } else {
                System.err.println(errorMessage);
            }
        }
    }

    public static class UndoAction extends UndoRedoAction {
        public UndoAction(UndoManager manager, String name) {
            super(manager, name);
            setErrorMessage("Cannot undo");
            setErrorTitle("Undo Problem");
        }

        public void actionPerformed(ActionEvent actionEvent) {
            try {
                undoManager.undo();
            } catch (CannotUndoException cannotUndoException) {
                showMessage(actionEvent.getSource());
            }
        }
    }

    public static class RedoAction extends UndoRedoAction {
        public RedoAction(UndoManager manager, String name) {
            super(manager, name);
            setErrorMessage("Cannot redo");
            setErrorTitle("Redo Problem");
        }

        public void actionPerformed(ActionEvent actionEvent) {
            try {
                undoManager.redo();
            } catch (CannotRedoException cannotRedoException) {
                showMessage(actionEvent.getSource());
            }
        }
    }
}

public class UndoSample {
    public static void main(String args[]) {
        JFrame frame = new JFrame("Undo Sample");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        JTextArea textArea = new JTextArea();
        JScrollPane scrollPane = new JScrollPane(textArea);

        UndoManager manager = new UndoManager();
        textArea.getDocument().addUndoableEditListener(manager);

        JToolBar toolbar = new JToolBar();
        JButton undoButton = new JButton(UndoManagerHelper.getUndoAction(manager));
        toolbar.add(undoButton);
        JButton redoButton = new JButton(UndoManagerHelper.getRedoAction(manager));
        toolbar.add(redoButton);
        frame.add(toolbar, BorderLayout.NORTH);
        frame.add(scrollPane, BorderLayout.CENTER);
        frame.setSize(300, 150);
        frame.setVisible(true);
    }
}