下面是根据你的代码改的，主要就是在线程中增加了while循环，否则时间不会更新的。
此外你的JFrame写到了JPanel之中，我就直接增加了显示的代码并增加了主方法，你可以试一下。
图片的路径已经修改了，你测试的时候需要改成你自己的。
import java.awt.GridLayout;
import java.awt.Image;
import java.awt.Panel;
import java.util.Date;
import javax.swing.ImageIcon;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.SwingConstants;
public class ClockDemo extends Panel implements Runnable {
/**
*
*/
private static final long serialVersionUID = -7055793302605026523L;
private JLabel imageLabel;
private JLabel localeLabel;
private JLabel dataLabel;
private JPanel panel;
private Thread t;
public ClockDemo(String city, String time) {
super();
panel = new JPanel();
imageLabel = new JLabel();
imageLabel.setLabelFor(imageLabel);
// 修改了图片的路径
ImageIcon imageL = new ImageIcon("D:\\Beijing.jpg");
imageL.setImage(imageL.getImage().getScaledInstance(50, 50,
Image.SCALE_DEFAULT));
imageLabel.setIcon(imageL);
imageLabel.setHorizontalAlignment(SwingConstants.CENTER);
localeLabel = new JLabel(city, JLabel.CENTER);// 城市名
dataLabel = new JLabel();
panel.setLayout(new GridLayout(3, 1));
panel.add(imageLabel);
panel.add(localeLabel);
panel.add(dataLabel);
JFrame jf = new JFrame();
jf.getContentPane().add(panel);
t = new Thread(this);
t.start();
// 增加的内容
jf.setLocationRelativeTo(null);
jf.setSize(300, 300);
jf.setVisible(true);
jf.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}
public void showTime() {
String str = "";
str = str + new Date();
dataLabel.setText(str);
dataLabel.setHorizontalAlignment(SwingConstants.CENTER);
}
@Override
public void run() {
// TODO Auto-generated method stub
// 没有while循环时间没有办法更新
while (true) {
try {
Thread.sleep(1000);
showTime();
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
// 主方法测试
@SuppressWarnings("unused")
public static void main(String[] args) {
ClockDemo clockDemo = new ClockDemo("beijing", null);
}
}
运行的结果如下所示：
此外，下面是我前段时间帮一个网友改的时间显示代码，你可以参考下，你上面的代码中JFrame使用的不是很好，不建议JPanel中使用JFrame，应该放到外面声明，然后将JPanel放到其中就行了。
这个样例主要是增加了绘制时钟的功能，可以显示一个简单地时间钟表，并且秒针是动的。你可以测试下。
import java.awt.Color;
import java.awt.Graphics;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
public class Clockone extends JFrame implements Runnable {
/**
*
*/
private static final long serialVersionUID = 8754113577355207407L;
private JPanel JP = new JPanel();
private Color C1 = new Color(123, 154, 45);
private SimpleDateFormat FM = new SimpleDateFormat(
"yyyy EEE MM dd HH:mm:ss");
private Date DT = new Date();
private Calendar C = Calendar.getInstance();
private int s, m, h;
private int XC = 101, YC = 101;
private int xs, ys, xm, ym, xh, yh;
private JLabel JL = new JLabel();
public Clockone(String title) {
super(title);
setLayout(null);
add(JP);
JP.setBounds(0, 0, 300, 300);
JP.setLayout(null);
JP.add(JL);
JL.setBounds(50, 50, 100, 50);
}
public void paint(Graphics g) {
g.clearRect(0, 0, this.getWidth(), this.getHeight());
g.setColor(Color.BLUE);
g.drawOval(50, 50, 100, 100);
g.drawOval(100, 100, 5, 5);
g.fillOval(XC, YC, 3, 3);
g.drawString("3", 143, 105);
g.drawString("6", 98, 150);
g.drawString("9", 51, 105);
g.drawString("12", 95, 62);
g.drawString("北京时间：" + String.valueOf((FM.format(DT))), 20, 200);
setBackground(C1);
s = C.get(Calendar.SECOND);
m = C.get(Calendar.MINUTE);
h = C.get(Calendar.HOUR_OF_DAY);
xs = (int) (Math.cos(s * Math.PI / 30 - Math.PI / 2) * 45 + XC);
ys = (int) (Math.sin(s * Math.PI / 30 - Math.PI / 2) * 45 + YC);
xm = (int) (Math.cos(m * Math.PI / 30 - Math.PI / 2) * 40 + XC);
ym = (int) (Math.sin(m * Math.PI / 30 - Math.PI / 2) * 40 + YC);
xh = (int) (Math.cos((h * 30 + m / 2) * Math.PI / 180 - Math.PI / 2) * 30 + XC);
yh = (int) (Math.sin((h * 30 + m / 2) * Math.PI / 180 - Math.PI / 2) * 30 + YC);
g.drawLine(xs, ys, XC, YC);
g.drawLine(xm, ym, XC - 1, YC);
g.drawLine(xm, ym, XC, YC - 1);
g.drawLine(xh, yh, XC - 1, YC);
g.drawLine(xh, yh, XC, YC - 1);
}
public void run() {
while (true) {
try {
Thread.sleep(1000);
C = Calendar.getInstance();
DT = C.getTime();
} catch (InterruptedException e) {
}
repaint();
}
}
public static void main(String[] args) {
Clockone CO = new Clockone("Clock");
CO.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
CO.setLocationRelativeTo(null);
CO.setSize(300, 300);
CO.setVisible(true);
Thread thread = new Thread(CO);
thread.start();
thread.setPriority(MAXIMIZED_BOTH);
}
}
