SwingWorkerTest.java Source code

Introduction

Here is the source code for SwingWorkerTest.java

Source

/*
 This program is a part of the companion code for Core Java 8th ed.
 (http://horstmann.com/corejava)
    
 This program is free software: you can redistribute it and/or modify
 it under the terms of the GNU General Public License as published by
 the Free Software Foundation, either version 3 of the License, or
 (at your option) any later version.
    
 This program is distributed in the hope that it will be useful,
 but WITHOUT ANY WARRANTY; without even the implied warranty of
 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 GNU General Public License for more details.
    
 You should have received a copy of the GNU General Public License
 along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

import java.awt.BorderLayout;
import java.awt.EventQueue;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.util.List;
import java.util.Scanner;
import java.util.concurrent.CancellationException;
import java.util.concurrent.ExecutionException;

import javax.swing.JFileChooser;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JMenu;
import javax.swing.JMenuBar;
import javax.swing.JMenuItem;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.SwingWorker;

/**
 * This program demonstrates a worker thread that runs a potentially
 * time-consuming task.
 * 
 * @version 1.1 2007-05-18
 * @author Cay Horstmann
 */
public class SwingWorkerTest {
    public static void main(String[] args) throws Exception {
        EventQueue.invokeLater(new Runnable() {
            public void run() {
                JFrame frame = new SwingWorkerFrame();
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.setVisible(true);
            }
        });
    }
}

/**
 * This frame has a text area to show the contents of a text file, a menu to
 * open a file and cancel the opening process, and a status line to show the
 * file loading progress.
 */
class SwingWorkerFrame extends JFrame {
    public SwingWorkerFrame() {
        chooser = new JFileChooser();
        chooser.setCurrentDirectory(new File("."));

        textArea = new JTextArea();
        add(new JScrollPane(textArea));
        setSize(DEFAULT_WIDTH, DEFAULT_HEIGHT);

        statusLine = new JLabel(" ");
        add(statusLine, BorderLayout.SOUTH);

        JMenuBar menuBar = new JMenuBar();
        setJMenuBar(menuBar);

        JMenu menu = new JMenu("File");
        menuBar.add(menu);

        openItem = new JMenuItem("Open");
        menu.add(openItem);
        openItem.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent event) {
                // show file chooser dialog
                int result = chooser.showOpenDialog(null);

                // if file selected, set it as icon of the label
                if (result == JFileChooser.APPROVE_OPTION) {
                    textArea.setText("");
                    openItem.setEnabled(false);
                    textReader = new TextReader(chooser.getSelectedFile());
                    textReader.execute();
                    cancelItem.setEnabled(true);
                }
            }
        });

        cancelItem = new JMenuItem("Cancel");
        menu.add(cancelItem);
        cancelItem.setEnabled(false);
        cancelItem.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent event) {
                textReader.cancel(true);
            }
        });
    }

    private class ProgressData {
        public int number;

        public String line;
    }

    private class TextReader extends SwingWorker<StringBuilder, ProgressData> {
        public TextReader(File file) {
            this.file = file;
        }

        // the following method executes in the worker thread; it doesn't touch
        // Swing components

        @Override
        public StringBuilder doInBackground() throws IOException, InterruptedException {
            int lineNumber = 0;
            Scanner in = new Scanner(new FileInputStream(file));
            while (in.hasNextLine()) {
                String line = in.nextLine();
                lineNumber++;
                text.append(line);
                text.append("\n");
                ProgressData data = new ProgressData();
                data.number = lineNumber;
                data.line = line;
                publish(data);
                Thread.sleep(1); // to test cancellation; no need to do this in your
                                 // programs
            }
            return text;
        }

        // the following methods execute in the event dispatch thread

        @Override
        public void process(List<ProgressData> data) {
            if (isCancelled())
                return;
            StringBuilder b = new StringBuilder();
            statusLine.setText("" + data.get(data.size() - 1).number);
            for (ProgressData d : data) {
                b.append(d.line);
                b.append("\n");
            }
            textArea.append(b.toString());
        }

        @Override
        public void done() {
            try {
                StringBuilder result = get();
                textArea.setText(result.toString());
                statusLine.setText("Done");
            } catch (InterruptedException ex) {
            } catch (CancellationException ex) {
                textArea.setText("");
                statusLine.setText("Cancelled");
            } catch (ExecutionException ex) {
                statusLine.setText("" + ex.getCause());
            }

            cancelItem.setEnabled(false);
            openItem.setEnabled(true);
        }

        private File file;

        private StringBuilder text = new StringBuilder();
    };

    private JFileChooser chooser;

    private JTextArea textArea;

    private JLabel statusLine;

    private JMenuItem openItem;

    private JMenuItem cancelItem;

    private SwingWorker<StringBuilder, ProgressData> textReader;

    public static final int DEFAULT_WIDTH = 450;

    public static final int DEFAULT_HEIGHT = 350;
}