SwingWorker 在多线程 Jframe 中答案

【问题标题】：SwingWorker In multithreaded JframesSwingWorker 在多线程 Jframe 中
【发布时间】：2013-12-23 08:16:04
【问题描述】：

我正在创建 4 个线程，每个线程都与一个 UI 相关联。 UI 执行一个长时间运行的任务，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，它的行为和运行方式为多线程。

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();
        }
    }
}

UI 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？

【问题讨论】：

标签： java multithreading swing swingworker

【解决方案1】：

嗯，不，这不是 Swing 中多线程的工作方式。

有一个单一的 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，因此执行类似...

@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;
}

实际上违反了这条规则。

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 方法的结果推回EDT。

SwingWorker 通过PropertyChange 支持拥有自己的进度支持

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;
            }

        }

    }

}

【讨论】：

要求是多个独立的 SwingWorker 线程，每个线程分配给自己的进程并同时更新 UI。
是的，这正是示例所做的。你不能做的是从事件调度线程之外更新 UI
您的示例正是我在示例中解释的内容。每个工作线程仅在单个时间更新其父 UI 并阻止其他工作线程。其他仅在第一个完成时运行。
好的，问题来了。这就是它的工作方式。 Swing 是一个单线程框架。所有对 ui 的交互和修改都必须在 EDT 的上下文中进行。虽然每个 SwingWorker 独立执行，但当 UI 更新时，所有更新都会同步回 EDT。这就是它的工作原理，没有其他方法可以做到这一点。其他任何事情充其量只会导致奇怪的图形伪影和不同步更新以及更严重的线程死锁。