Java Swing How to - Start and stop SwingWorker

Question

We would like to know how to start and stop SwingWorker.
Answer

//w w  w  .  jav  a  2 s  . com
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.ArrayList;

import javax.swing.DefaultListModel;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JList;
import javax.swing.JProgressBar;
import javax.swing.JScrollPane;

public class Main extends JFrame implements ActionListener {
  private final JButton startButton, stopButton;
  private JScrollPane scrollPane = new JScrollPane();
  private JList listBox = null;
  private DefaultListModel listModel = new DefaultListModel();
  private final JProgressBar progressBar;
  private mySwingWorker swingWorker;

  public Main() {
    super();
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    getContentPane().setLayout(new GridLayout(4, 1));
    startButton = makeButton("Start");
    stopButton = makeButton("Stop");
    stopButton.setEnabled(false);
    progressBar = makeProgressBar(0, 99);
    listBox = new JList(listModel);
    scrollPane.setViewportView(listBox);
    add(scrollPane);
    pack();
    setVisible(true);
  }

  private class mySwingWorker extends
      javax.swing.SwingWorker<ArrayList<Integer>, Integer> {
    @Override
    protected ArrayList<Integer> doInBackground() {
      if (javax.swing.SwingUtilities.isEventDispatchThread()) {
        System.out.println("javax.swing.SwingUtilities.isEventDispatchThread() returned true.");
      }
      ArrayList<Integer> list = new ArrayList<Integer>();
      for (int i = 0; i < 100; i++) {
        try {
          Thread.sleep(1000);
        } catch (Exception e) {
          e.printStackTrace();
        }
        if (isCancelled()) {
          System.out.println("SwingWorker - isCancelled");
          return list;
        }
        publish(new Integer(i));
        list.add(i);
      }
      return list;
    }

    @Override
    protected void process(java.util.List<Integer> progressList) {
      if (!javax.swing.SwingUtilities.isEventDispatchThread()) {
        System.out.println("javax.swing.SwingUtilities.isEventDispatchThread() + returned false.");
      }
      Integer percentComplete = progressList.get(progressList.size() - 1);
      progressBar.setValue(percentComplete.intValue());
    }

    @Override
    protected void done() {
      if (!javax.swing.SwingUtilities.isEventDispatchThread()) {
        System.out.println("javax.swing.SwingUtilities.isEventDispatchThread() + returned false.");
      }
      try {
        ArrayList<Integer> results = get();
        for (Integer i : results) {
          listModel.addElement(i.toString());
        }
      } catch (Exception e) {
        System.out.println("Caught an exception: " + e);
      }
      startButton();
    }

  }

  private JButton makeButton(String caption) {
    JButton b = new JButton(caption);
    b.setActionCommand(caption);
    b.addActionListener(this);
    getContentPane().add(b);
    return b;
  }

  private JProgressBar makeProgressBar(int min, int max) {
    JProgressBar progressBar1 = new JProgressBar();
    progressBar1.setMinimum(min);
    progressBar1.setMaximum(max);
    progressBar1.setStringPainted(true);
    progressBar1.setBorderPainted(true);
    getContentPane().add(progressBar1);
    return progressBar1;
  }

  private void startButton() {
    startButton.setEnabled(true);
    stopButton.setEnabled(false);
  }

  @Override
  public void actionPerformed(ActionEvent e) {
    if ("Start" == null ? e.getActionCommand() == null : "Start".equals(e
        .getActionCommand())) {
      startButton.setEnabled(false);
      stopButton.setEnabled(true);
      (swingWorker = new mySwingWorker()).execute();
    } else if ("Stop" == null ? e.getActionCommand() == null : "Stop".equals(e
        .getActionCommand())) {
      startButton.setEnabled(true);
      stopButton.setEnabled(false);
      swingWorker.cancel(true);
      swingWorker = null;
    }
  }

  public static void main(String[] args) {
    new Main();
  }
}