根据我之前的问题What';拥有一个动态JTable的最佳方式是,它的数据会随着数据库表中的变化而更新,我使用了以下代码自动更新jList
DefaultListModel x = new DefaultListModel();
jList1.setModel(x);
int initialDelay = 0;
int period = 5000;
Timer timer = new Timer();
TimerTask task = new TimerTask() {
public void run() {
x.clear();
try {
conn = Database.Connect("patient.db");
sql = "SELECT * FROM PATIENT_APPOINTMENTS";
pst = conn.prepareStatement(sql);
rs = pst.executeQuery();
while(rs.next()) {
x.addElement(rs.getString("patientid"));
}
}
catch ( Exception e) {
JOptionPane.showMessageDialog(null,e,"Error",JOptionPane.ERROR_MESSAGE);
}
}
};
timer.scheduleAtFixedRate(task,initialDelay,period);
但我读过关于SwingWorker的文章,这似乎是正确的方法。SwingWorkers的正常实现有doInBackground、publish和done三种受保护的方法。我还尝试了SwingWorker的另一个版本,即
DefaultListModel x = new DefaultListModel();
jList1.setModel(x);
int initialDelay = 0;
int period = 5000;
Timer timer = new Timer();
TimerTask task = new TimerTask() {
public void run() {
x.clear();
try {
SwingWorker<ArrayList<String>, Void> worker = new SwingWorker<ArrayList<String>, Void>() {
protected ArrayList<String> doInBackground() throws Exception {
ArrayList<String> patientid = new ArrayList<String>();
conn = Database.Connect("patient.db");
sql = "SELECT * FROM PATIENT_APPOINTMENTS";
pst = conn.prepareStatement(sql);
rs = pst.executeQuery();
while (rs.next()) {
patientid.add(rs.getString("patientid"));
}
return patientid;
}
protected void done() {
ArrayList<String> id = new ArrayList<String>();
try {
id = get();
for (int i = 0; i < id.size(); i++) {
x.addElement(id.get(i));
}
} catch (InterruptedException e) {
JOptionPane.showMessageDialog(null, e, "Error", JOptionPane.ERROR_MESSAGE);
} catch (ExecutionException e) {
JOptionPane.showMessageDialog(null, e, "Error", JOptionPane.ERROR_MESSAGE);
}
}
};
worker.execute();
} catch (Exception e) {
JOptionPane.showMessageDialog(null, e, "Error", JOptionPane.ERROR_MESSAGE);
}
}
};
timer.scheduleAtFixedRate(task, initialDelay, period);
}
哪种方法更好?此外,jList每5秒闪烁5次,我该如何避免这种情况?
Swing Timer
在事件调度线程的上下文中执行其通知,使其适合更新UI,但不适合执行长时间运行或块任务(如查询数据库)
Thread
适用于执行长时间运行或块任务,但不应用于更新UI,因为Swing不是线程安全的,并且只能在EDT的上下文中修改UI。当然你可以使用EventQueue.invokeLater
,但如果你需要为这些调用提供参数,这会变得很痛苦。。。
您可以使用SwingWorker
,它能够在后台(EDT之外)执行长时间运行或阻塞任务,但提供了更新UI的方法,通过它的publish
/process
、done
和/或PropertyChange
支持
看看:
- Swing中的并发
- 如何使用摆动计时器
- Worker线程和SwingWorker
有关更多详细信息,
哪种方法更好
你的第一个例子违反了Swing的单线程规则,所以它没有多大用处。。。
您的第二个例子是overkill,TimerTask
已经在后台运行,实际上您最好使用ScheduledExecutorService
并将SwingWorker
的实例传递给它。。。
更新
这不是我希望的方式,但是。。。
import java.awt.EventQueue;
import java.awt.GridBagLayout;
import java.beans.PropertyChangeEvent;
import java.beans.PropertyChangeListener;
import java.util.List;
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.TimeUnit;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.SwingWorker;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
public class Test {
public static void main(String[] args) {
new Test();
}
public Test() {
EventQueue.invokeLater(new Runnable() {
@Override
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
ex.printStackTrace();
}
JFrame frame = new JFrame("Testing");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(new TestPane());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
public class TestPane extends JPanel {
private JLabel label;
private int count;
private ScheduledExecutorService service = Executors.newScheduledThreadPool(1);
public TestPane() {
setLayout(new GridBagLayout());
label = new JLabel("...");
add(label);
service.schedule(new CounterWorker(), 1, TimeUnit.SECONDS);
}
public class CounterWorker extends SwingWorker<Integer, Integer> {
@Override
protected Integer doInBackground() throws Exception {
System.out.println("Tick");
for (int index = 0; index < 100; index++) {
count++;
publish(count);
Thread.yield();
}
return count;
}
@Override
protected void process(List<Integer> chunks) {
label.setText(Integer.toString(chunks.get(chunks.size() - 1)));
}
@Override
protected void done() {
service.schedule(new CounterWorker(), 1, TimeUnit.SECONDS);
}
}
}
}