我有一个基本的Swing UI,带有一个标记为“播放”的按钮。当按下按钮时,标签变为“暂停”。现在,当按下按钮时,它变为“继续”。
在“播放”中,我将实例化并执行一个SwingWorker。我想要的是能够暂停该线程(不要取消该线程),并根据上述按钮按下来恢复它。但是,我不想在doInBackground()中求助于Thread.sleep()。这似乎有点骇人听闻。有什么方法可以阻止运行doInBackground的线程?
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());
}
}
});
这是一个完整的示例。请注意,如果工人停止了,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;
}
}
}
本文收集自互联网,转载请注明来源。
如有侵权,请联系[email protected] 删除。
我来说两句