MainClass.java Source code

Introduction

Here is the source code for MainClass.java

Source

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

import javax.swing.AbstractAction;
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.CannotUndoException;
import javax.swing.undo.UndoManager;

public class MainClass {

    public static void main(final 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(
                new UndoAction(manager, (String) UIManager.get("AbstractUndoableEdit.undoText")));
        toolbar.add(undoButton);

        Container content = frame.getContentPane();
        content.add(toolbar, BorderLayout.NORTH);
        content.add(scrollPane, BorderLayout.CENTER);
        frame.setSize(300, 150);
        frame.setVisible(true);

    }
}

abstract 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);
        }
    }
}

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());
        }
    }
}