Periodically update JLabel in GUI - how?
Hi everybody,
I'm trying to write a status bar for my Swing application that should periodically (every 5 s or so) update the current time. I'm trying to do as follows, but the GUI blocks, when the while-loop is enabled, completely, and when removed, it blocks the whole 5 s. What am I doing wrong? As far as I could find out, the new Thread should be run by invokeAnd Wait() ...
mainWindow.setVisible(true);
try{
SwingUtilities.invokeAndWait(new Runnable(){
publicvoid run(){
while(true){
try{
Thread.sleep(500);
}catch (InterruptedException e){
e.printStackTrace();
}
mainWindow.updateStatusBar("test");
}
}
});
}catch (InterruptedException e){
e.printStackTrace();
}catch (InvocationTargetException e){
e.printStackTrace();
}
Thanks, Steffi
[1686 byte] By [
steffaniea] at [2007-10-1 5:04:58]
Hi!
I created a demo programm, that updates the GUI after every 5 seconds. Sorry i don't know exactly, why your program doesn't work. I guess, because invokeAndWait() blocks, until the function run() calls return.
import java.awt.Frame;
import java.util.Date;
import java.awt.Color;
import java.lang.Thread;
import java.awt.Event;
import java.awt.Graphics;
import java.lang.InterruptedException;
import java.awt.Font;
/*
To refresh the GUI, and periodically show the current system time, there is a thread
Timer, that communicates with the class test (invoking callback()@test).
*/
public class test extends Frame
{
private Date time_stamp;
private static String[] string_numbers = { "00", "01", "02", "03", "04", "05", "06",
"07", "08", "09" };
private Thread refresh;
private Font f;
public test() {
super("Shows time...");
time_stamp = new Date();
resize(400, 100);
show();
f = new Font("Dialog", Font.PLAIN, 14);
refresh = new Timer(this);
refresh.start();
}
public boolean handleEvent(Event e) { //this is used only, if you close the window
if (e.target == this && e.id == Event.WINDOW_DESTROY) {
hide();
System.exit(1);
}
return super.handleEvent(e);
}
//creates a time string in this form: <hour:min:sec>
private String createTimeString() {
long tmp;
String time = "<";
time_stamp.setTime(System.currentTimeMillis());
if( (tmp=time_stamp.getHours())<10 )
time = time + string_numbers[(int)tmp] + ":";
else time = time + tmp + ":";
if( (tmp=time_stamp.getMinutes())<10 )
time = time + string_numbers[(int)tmp] + ":";
else time = time + tmp + ":";
if( (tmp=time_stamp.getSeconds())<10 )
time = time + string_numbers[(int)tmp] + ":";
else time = time + tmp + ":";
time = time + "> ";
return time;
}
public void paint(Graphics g) {
String current_time = createTimeString();
super.paint(g);
g.setFont(f);
g.setColor(Color.white); //sets the background color to white to clear this window
g.fillRect(0, 0, size().width, size().height);
g.setColor(Color.black); //sets the color back to black to draw the string
g.drawString(current_time, 40, 40); //draws the current time
}
public void callback() { //this function will be called from the thread Timer to "talk back" to
repaint(); //this object.
//If you call repaint(), the AWTThread will call paint() in this class!
}
public static void main(String args[]) {
test tmp = new test();
while(true) {
System.out.println("You can make hier anything without being blocked...");
}
}
}
class Timer extends Thread
{
private test parent;
public Timer(test t) {
parent = t;
}
synchronized public void run() {
while(true) {
try{
wait(5000);
}catch(InterruptedException ie) {return;}
parent.callback();
}
}
}
Hope this is what you asked...
