暂停和恢复SwingWorker.doInBackground（）

暂停和恢复SwingWorker.doInBackground（）

暂停和恢复SwingWorker.doInBackground（）

首先，您必须确保可以暂停正在执行的后台任务，否则问题就没有意义了。所以我们可以说任务可以暂停，那么你可能会延长的SwingWorker类，使自己
可暂停 使用一个简单的标志变量来控制后台线程状态的工人： 暂停 或 不暂停 。

public abstract class PausableSwingWorker<K, V> extends SwingWorker<K, V> {    private volatile boolean isPaused;    public final void pause() {        if (!isPaused() && !isDone()) { isPaused = true; firePropertyChange("paused", false, true);        }    }    public final void resume() {        if (isPaused() && !isDone()) { isPaused = false; firePropertyChange("paused", true, false);        }    }    public final boolean isPaused() {        return isPaused;    }}

子类可能会检查

isPaused()

状态，以便有效地继续执行任务。例如：

PausableSwingWorker<Void, String> worker = new PausableSwingWorker<Void, String>() {    @Override    protected Void doInBackground() throws Exception {        while (!isCancelled()) { if (!isPaused()) {     // proceed with background task } else {     Thread.sleep(200); // Optional sleep to avoid check status continuously }        }        return null;    }};

您还可以向工作器添加PropertyChangeListener并侦听

paused

属性更改：

worker.addPropertyChangeListener(new PropertyChangeListener() {    @Override    public void propertyChange(PropertyChangeEvent evt) {        if ("paused".equals(evt.getPropertyName())) {System.out.println("Old status: " + evt.getOldValue());System.out.println("New status: " + evt.getNewValue());        }    }});

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示例（已更新，以使用PropertyChangeListener）

这是一个完整的示例。请注意，如果工作者已停止，则无法再暂停或恢复它。

import java.awt.BorderLayout;import java.awt.FlowLayout;import java.awt.event.ActionEvent;import java.awt.event.WindowAdapter;import java.awt.event.WindowEvent;import java.beans.PropertyChangeEvent;import java.beans.PropertyChangeListener;import java.util.List;import javax.swing.AbstractAction;import javax.swing.Action;import javax.swing.BorderFactory;import javax.swing.JButton;import javax.swing.Jframe;import javax.swing.JPanel;import javax.swing.JScrollPane;import javax.swing.Jtextarea;import javax.swing.SwingUtilities;import javax.swing.SwingWorker;public class Demo {    private void createAndShowGUI() {        final Jtextarea textarea = new Jtextarea(20, 50);        final PausableSwingWorker<Void, String> worker = new PausableSwingWorker<Void, String>() { @Override protected Void doInBackground() throws Exception {     while (!isCancelled()) {         if (!isPaused()) {  publish("Writing...");         } else {  Thread.sleep(200);         }     }     return null; } @Override protected void process(List<String> chunks) {     String text = String.format("%s%n", chunks.get(chunks.size() - 1));     textarea.append(text); }        };        worker.addPropertyChangeListener(new PropertyChangeListener() { @Override public void propertyChange(PropertyChangeEvent evt) {     if ("paused".equals(evt.getPropertyName())) {         String text = (Boolean)evt.getNewValue() ? "Paused..." : "Resumed...";         textarea.append(String.format("%s%n", text));     } }        });        Action pause = new AbstractAction("Pause") { @Override public void actionPerformed(ActionEvent e) {     worker.pause(); }        };        Action resume = new AbstractAction("Resume") { @Override public void actionPerformed(ActionEvent e) {     worker.resume(); }        };        Action stop = new AbstractAction("Stop") { @Override public void actionPerformed(ActionEvent e) {     worker.cancel(true); }        };        JPanel buttonsPanel = new JPanel(new FlowLayout(FlowLayout.CENTER));        buttonsPanel.add(new JButton(pause));        buttonsPanel.add(new JButton(resume));        buttonsPanel.add(new JButton(stop));        JPanel content = new JPanel(new BorderLayout(8, 8));        content.setBorder(BorderFactory.createEmptyBorder(8, 8, 8, 8));        content.add(new JScrollPane(textarea), BorderLayout.CENTER);        content.add(buttonsPanel, BorderLayout.SOUTH);        Jframe frame = new Jframe("Demo");        frame.setDefaultCloseOperation(Jframe.DO_NOTHING_ON_CLOSE);        frame.addWindowListener(new WindowAdapter() { @Override public void windowClosing(WindowEvent e) {     if (!worker.isDone()) {         worker.cancel(true);     }     e.getWindow().dispose(); }        });        frame.add(content);        frame.pack();        frame.setLocationByPlatform(true);        frame.setVisible(true);        worker.execute();    }    public static void main(String[] args) {        SwingUtilities.invokeLater(new Runnable() { @Override public void run() {     new Demo().createAndShowGUI(); }        });    }    abstract class PausableSwingWorker<K, V> extends SwingWorker<K, V> {        private volatile boolean isPaused;        public final void pause() { if (!isPaused() && !isDone()) {     isPaused = true;     firePropertyChange("paused", false, true); }        }        public final void resume() { if (isPaused() && !isDone()) {     isPaused = false;     firePropertyChange("paused", true, false); }        }        public final boolean isPaused() { return isPaused;        }    }}