在我的电子邮件程序的一部分中，用户可以通过下拉列表JComboBox选择要打开的邮件文件夹。此过程最多可能需要20秒，具体取决于文件夹中的消息数量，在此之前只会冻结程序。这是不可取的，所以我使用SwingWorker在GUI的背景中运行文件夹的打开，并在访问文件夹时显示进度条。
使用ActionListener实现文件夹的访问，该String侦听所选的文件夹名称，并将选定的ActionListener设置为要访问的文件夹的名称。以下是 box = new JComboBox<String>(items);
box.setEditable(false);
box.addActionListener(new ActionListener()
{
public void actionPerformed(ActionEvent e)
{
try
{
String selected = (String)box.getSelectedItem();
if(selected.equals("Choose Folder"))
accessFolder(null);
else if(selected.equals("Inbox"))
accessFolder("INBOX");
else
{
selected = TAG + selected;
accessFolder(selected);
}
}
catch(Exception ex)
{
JOptionPane.showMessageDialog(null, "Error: " +
ex.getClass().getName(), "Error", JOptionPane.ERROR_MESSAGE);
}
}
});
的代码，其中items是文件夹名称数组。
accessFolder此代码的最终结果符合预期：所有消息的列表将添加到主框架的一部分。但进度条永远不会出现。但是，如果我将ActionListener方法的代码直接添加到main方法（将accessFolder添加到组合框中），则进度条会显示整个进程，我得到了同样的最终结果。这是private void accessFolder(String folderName) throws MessagingException, IOException
{
MessagePanel mPanel = new MessagePanel(username, password, folderName);
panel4 = mPanel.getJPanel();
panel4.setBorder(BorderFactory.createLoweredBevelBorder());
BorderLayout layout = (BorderLayout)panel3.getLayout();
panel3.remove(layout.getLayoutComponent(BorderLayout.EAST));
panel3.add(panel4, BorderLayout.EAST);
frame.pack();
frame.revalidate();
}
代码。
MessagePanel所以我似乎无法弄清楚为什么SwingWorker（在accessFolder中的ActionListener类中实现）在代码中的任何地方都可以正常工作，除了SwingWorker。我似乎无法在任何地方找到public class FolderWorker extends CMailWorker
{
private String username;
private String password;
private String foldername;
private FolderContents accessor;
private ArrayList<MailList> msgList;
private DefaultListModel<String> model;
private ProgressBar bar;
private final static String PENDING = "Accessing...";
public FolderWorker(String user, String pass, String fName)
{
super(PENDING, null);
this.username = user;
this.password = pass;
this.foldername = fName;
}
protected Void doInBackground()
{
try
{
SwingUtilities.invokeLater(new Runnable()
{
public void run()
{
try
{
createProgressBar();
}
catch(Exception ex)
{
setException(ex);
}
}
});
super.throwException();
accessor = new FolderContents(username, password, foldername);
model = new DefaultListModel<String>();
msgList = accessor.getMessageList();
for(int x = msgList.size()-1; x>=0; x--)
{
MailList mList = msgList.get(x);
String sub = mList.getSubject();
model.addElement(sub);
}
return null;
}
catch(final Exception ex)
{
SwingUtilities.invokeLater(new Runnable()
{
public void run()
{
JOptionPane.showMessageDialog(null, "Error: " +
ex.getClass().getName(), "Error", JOptionPane.ERROR_MESSAGE);
}
});
super.setError(true);
return null;
}
}
public ArrayList<MailList> getList()
{
return accessor.getMessageList();
}
public DefaultListModel<String> getModel()
{
return model;
}
}
和听众之间的冲突，我不明白为什么会这样，让我完全不知所措。感谢您的任何意见。
编辑：这是SwingWorker代码。
public class CMailWorker extends SwingWorker<Void, Void>
{
private ProgressBar bar;
private String completed;
private String message;
private boolean error;
private JFrame frame;
private Exception exception;
public CMailWorker(String msg, String done)
{
completed = done;
message = msg;
error = false;
}
protected Void doInBackground()
{
return null;
}
protected void done()
{
bar.dispose();
if(frame != null)
killJFrame();
if(!error && completed != null)
JOptionPane.showMessageDialog(null, completed);
}
protected void setJFrame(JFrame f)
{
frame = f;
}
private void killJFrame()
{
frame.dispose();
}
protected void createProgressBar() throws InterruptedException
{
bar = new ProgressBar(message);
}
protected void setError(boolean e)
{
error = e;
}
protected boolean getError()
{
return error;
}
protected void throwException() throws Exception
{
if(exception != null)
throw exception;
}
protected void setException(Exception e)
{
exception = e;
}
protected Exception getException()
{
return exception;
}
}
该课程扩展了这门课程。
Intent intent = new Intent(this, MyActivity.class);
TaskStackBuilder stackBuilder = TaskStackBuilder.create(this);
stackBuilder.addNextIntentWithParentStack(intent);
stackBuilder.startActivities();