java - 多线程 Jframes 中的 SwingWorker

Question

我正在创建 4 个线程，每个线程都与一个 UI 相关联。UI 执行长时间运行的任务，为此我使用了 SwingWorker。但是出现的问题是它不是作为多线程应用程序运行，而是在队列中运行。

有趣的是，当我删除 SwingWorker 时，它会以多线程方式运行。

我的代码如下:

新类

package thread;

public class NewClass
{
    public static void main(String[] args) throws Exception
    {
        for(int i=0; i<4 ; i++)
        {
            new ThreadFront().startsThread();
            Thread.sleep(2000);
        } 
    }
}

class ThreadFront implements Runnable
{
    private Thread t;

    public ThreadFront() 
    {
        t = new Thread(this, "");

    }

    public void startsThread()
    {
        t.start();
    }

    @Override
    public void run()
    {
        try
        {
            UI ui = new UI();
            ui.startThread();
        }
        catch(Exception ae)
        {
            ae.printStackTrace();
        }
    }
}

界面类

package thread;

import java.util.List;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.swing.JFrame;
import javax.swing.SwingWorker;

public class UI extends javax.swing.JFrame
{
    public UI()
    {
        initComponents();    
        setVisible(true); 
    }

    public void startThread() throws Exception
    {       
        new SwingWorker<Integer, Integer>()
        {
            @Override
            protected Integer doInBackground() throws Exception 
            {                
                for(int i=0; i<10;i++)
                {
                    jTextArea1.append(""+i);
                    Thread.sleep(3000);
                }
                return 0;
            }

            @Override
            protected void process(List<Integer> chunks) 
            {
                for(Integer message : chunks)
                {
                    jProgressBar1.setValue(message); 
                    jProgressBar1.repaint();
                }
            }

            @Override
            protected void done() 
            {
                try 
                {
                    get();
                }
                catch(final Exception ex) 
                {
                    ex.printStackTrace();
                }
            }
        }.execute();
    }

    // <editor-fold defaultstate="collapsed" desc="Generated Code">                          
    private void initComponents() {

        jPanel1 = new javax.swing.JPanel();
        jPanel2 = new javax.swing.JPanel();
        jLabel1 = new javax.swing.JLabel();
        jPanel3 = new javax.swing.JPanel();
        jScrollPane1 = new javax.swing.JScrollPane();
        jTextArea1 = new javax.swing.JTextArea();
        jLabel2 = new javax.swing.JLabel();
        jobid_field = new javax.swing.JLabel();
        jProgressBar1 = new javax.swing.JProgressBar();
        work_field = new javax.swing.JLabel();
        jLabel4 = new javax.swing.JLabel();
        jLabel3 = new javax.swing.JLabel();
        session_field = new javax.swing.JLabel();

        setDefaultCloseOperation(javax.swing.WindowConstants.DISPOSE_ON_CLOSE);
        setLocationByPlatform(true);
        setResizable(false);
        addWindowListener(new java.awt.event.WindowAdapter() {
            public void windowClosing(java.awt.event.WindowEvent evt) {
                formWindowClosing(evt);
            }
        });

        jPanel1.setLayout(new java.awt.BorderLayout());

        jPanel2.setBackground(new java.awt.Color(204, 204, 204));
        jPanel2.setBorder(javax.swing.BorderFactory.createMatteBorder(1, 1, 1, 1, new java.awt.Color(255, 255, 255)));
        jPanel2.setForeground(new java.awt.Color(204, 204, 204));

        jLabel1.setFont(new java.awt.Font("Century Gothic", 1, 14)); // NOI18N
        jLabel1.setText("iZoneX Math Process");

        javax.swing.GroupLayout jPanel2Layout = new javax.swing.GroupLayout(jPanel2);
        jPanel2.setLayout(jPanel2Layout);
        jPanel2Layout.setHorizontalGroup(
            jPanel2Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(jPanel2Layout.createSequentialGroup()
                .addGap(18, 18, 18)
                .addComponent(jLabel1, javax.swing.GroupLayout.PREFERRED_SIZE, 304, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addContainerGap(86, Short.MAX_VALUE))
        );
        jPanel2Layout.setVerticalGroup(
            jPanel2Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(jPanel2Layout.createSequentialGroup()
                .addContainerGap()
                .addComponent(jLabel1, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                .addContainerGap())
        );

        jPanel1.add(jPanel2, java.awt.BorderLayout.NORTH);

        jPanel3.setBackground(new java.awt.Color(204, 204, 204));
        jPanel3.setBorder(javax.swing.BorderFactory.createMatteBorder(1, 1, 1, 1, new java.awt.Color(255, 255, 255)));

        jTextArea1.setEditable(false);
        jTextArea1.setBackground(new java.awt.Color(255, 255, 204));
        jTextArea1.setColumns(20);
        jTextArea1.setFont(new java.awt.Font("Century Gothic", 1, 12)); // NOI18N
        jTextArea1.setForeground(new java.awt.Color(255, 0, 0));
        jTextArea1.setLineWrap(true);
        jTextArea1.setRows(5);
        jTextArea1.setWrapStyleWord(true);
        jScrollPane1.setViewportView(jTextArea1);

        jLabel2.setText("Job ID. :");

        jLabel4.setText("Processing: ");

        jLabel3.setText("Session ID: ");

        javax.swing.GroupLayout jPanel3Layout = new javax.swing.GroupLayout(jPanel3);
        jPanel3.setLayout(jPanel3Layout);
        jPanel3Layout.setHorizontalGroup(
            jPanel3Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(javax.swing.GroupLayout.Alignment.TRAILING, jPanel3Layout.createSequentialGroup()
                .addContainerGap()
                .addGroup(jPanel3Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.TRAILING)
                    .addComponent(jScrollPane1, javax.swing.GroupLayout.Alignment.LEADING)
                    .addGroup(javax.swing.GroupLayout.Alignment.LEADING, jPanel3Layout.createSequentialGroup()
                        .addComponent(jLabel2)
                        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                        .addComponent(jobid_field, javax.swing.GroupLayout.PREFERRED_SIZE, 115, javax.swing.GroupLayout.PREFERRED_SIZE)
                        .addGap(33, 33, 33)
                        .addComponent(jLabel3)
                        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                        .addComponent(session_field, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
                    .addComponent(jProgressBar1, javax.swing.GroupLayout.Alignment.LEADING, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                    .addGroup(jPanel3Layout.createSequentialGroup()
                        .addComponent(jLabel4, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
                        .addComponent(work_field, javax.swing.GroupLayout.PREFERRED_SIZE, 320, javax.swing.GroupLayout.PREFERRED_SIZE)))
                .addContainerGap())
        );
        jPanel3Layout.setVerticalGroup(
            jPanel3Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(jPanel3Layout.createSequentialGroup()
                .addContainerGap()
                .addGroup(jPanel3Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.TRAILING, false)
                    .addComponent(jLabel2, javax.swing.GroupLayout.Alignment.LEADING, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                    .addComponent(jobid_field, javax.swing.GroupLayout.Alignment.LEADING, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                    .addComponent(jLabel3)
                    .addComponent(session_field, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                .addComponent(jScrollPane1, javax.swing.GroupLayout.PREFERRED_SIZE, 148, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
                .addComponent(jProgressBar1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                .addGroup(jPanel3Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                    .addComponent(work_field, javax.swing.GroupLayout.PREFERRED_SIZE, 22, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addComponent(jLabel4, javax.swing.GroupLayout.PREFERRED_SIZE, 18, javax.swing.GroupLayout.PREFERRED_SIZE))
                .addContainerGap())
        );

        jPanel1.add(jPanel3, java.awt.BorderLayout.CENTER);

        getContentPane().add(jPanel1, java.awt.BorderLayout.CENTER);

        pack();
    }// </editor-fold>                        

    private void formWindowClosing(java.awt.event.WindowEvent evt) {                                   

    }                                  

    // Variables declaration - do not modify                     
    private javax.swing.JLabel jLabel1;
    private javax.swing.JLabel jLabel2;
    private javax.swing.JLabel jLabel3;
    private javax.swing.JLabel jLabel4;
    private javax.swing.JPanel jPanel1;
    private javax.swing.JPanel jPanel2;
    private javax.swing.JPanel jPanel3;
    private javax.swing.JProgressBar jProgressBar1;
    private javax.swing.JScrollPane jScrollPane1;
    private javax.swing.JTextArea jTextArea1;
    private javax.swing.JLabel jobid_field;
    private javax.swing.JLabel session_field;
    private javax.swing.JLabel work_field;
    // End of variables declaration                   

}

在这种情况下，Swing 中工作线程的替代方案是什么？

Answer 1

嗯，不，这不是多线程在 Swing 中的工作方式。

只有一个 UI 线程(称为事件调度线程)，所有更新和与 UI 的交互都应在 EDT 的上下文中完成，因此执行诸如...

@Override
public void run()
{
    try
    {
        UI ui = new UI();
        ui.startThread();
    }
    catch(Exception ae)
    {
        ae.printStackTrace();
    }
}

还有……

@Override
protected Integer doInBackground() throws Exception 
{                
    for(int i=0; i<10;i++)
    {
        jTextArea1.append(""+i);
        Thread.sleep(3000);
    }
    return 0;
}

实际上是在违反这个规则。

相反，每个 UI 都应该有自己的 SwingWorker(就像现在一样)，但应该在 EDT 的上下文中创建。

每个 SwingWorker 都应该调用 publish 以便将 doInBackground 方法的结果推送回 EDT。

SwingWorker 通过 PropertyChange 支持有自己的进度支持

例如……

import java.awt.BorderLayout;
import java.awt.EventQueue;
import java.awt.GridLayout;
import java.beans.PropertyChangeEvent;
import java.beans.PropertyChangeListener;
import java.util.ArrayList;
import java.util.List;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JProgressBar;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.SwingUtilities;
import javax.swing.SwingWorker;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;

public class MultiThreadedUI {

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

    public MultiThreadedUI() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                    ex.printStackTrace();
                }

                final List<TestPane> panes = new ArrayList<>(5);
                for (int index = 0; index < 5; index++) {
                    panes.add(new TestPane(Integer.toString(index)));
                }

                JFrame frame = new JFrame("Testing");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.setLayout(new GridLayout(0, 1));
                for (TestPane pane : panes) {
                    frame.add(pane);
                }
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);

                SwingUtilities.invokeLater(new Runnable() {
                    @Override
                    public void run() {
                        for (TestPane pane : panes) {
                            pane.makeItSo();
                        }
                    }
                });
            }
        });
    }

    public class TestPane extends JPanel {

        private JTextArea textArea;
        private JProgressBar pb;
        private String name;

        public TestPane(String name) {
            this.name = name;
            textArea = new JTextArea(10, 5);
            pb = new JProgressBar();
            setLayout(new BorderLayout());
            add(new JScrollPane(textArea));
            add(pb, BorderLayout.SOUTH);
        }

        public void makeItSo() {

            BackgroundWorker worker = new BackgroundWorker();
            worker.addPropertyChangeListener(new PropertyChangeListener() {
                @Override
                public void propertyChange(PropertyChangeEvent evt) {
                    if ("progress".equalsIgnoreCase(evt.getPropertyName())) {
                        pb.setValue((Integer)evt.getNewValue());
                    }
                }
            });
            worker.execute();

        }

        protected class BackgroundWorker extends SwingWorker<Integer, Integer> {

            @Override
            protected void process(List<Integer> chunks) {
                for (Integer value : chunks) {
                    textArea.append(name + ": " + value + "\n");
                }
            }

            @Override
            protected Integer doInBackground() throws Exception {
                int delay = (int)(Math.random() * 3000);
                for (int i = 0; i < 10; i++) {
                    publish(i);
                    setProgress((int) (Math.round(((double) i / (double) 9) * 100)));
                    Thread.sleep(delay);
                }
                return 0;
            }

        }

    }

}