public class TimerProgram extends JFrame {
public TimerProgram(){
int DELAY=1000;
Timer t = new Timer(DELAY,new TimerListener());
t.start();
}
class TimerListener implements ActionListener{
public void actionPerformed(ActionEvent e) {
System.out.println("Hello");
}
}
public static void main(String[]args){
new TimerProgram();
}
}
I am trying to make a timer that outputs every second the word hello, but it seems that when I type as the DELAY value 1000 , it outputs hello once and then it terminates. What am I doing wrong ? All help appreciated!
The JVM exited before the Timer fired.
Try:
t.setInitialDelay(0);
t.start();
to see the difference.
Or a better approach is to execute the code on the Event Dispatch Thread (EDT). All GUI code should execute on the EDT. By using SwingUtitities.invokeLater() you ensure the EDT has been created when your code executes:
EventQueue.invokeLater(new Runnable()
{
public void run()
{
new TimerProgram();
}
});
Read the section from the Swing tutorial on Concurrency for more information about the EDT.
Related
Im not really an expert in programming and Im just starting to learn. Here is my problem.
I tried to call this class to start the server using a JButton but after the button was pressed the application freezes.
Here is my mouseClicked event
private void startbtnActionPerformed(java.awt.event.ActionEvent evt) {
new DisplayServer(80);
}
I suppose you block the Event Dispatcher Thread. Try to run it in a new Thread.
private void startbtnActionPerformed(java.awt.event.ActionEvent evt) {
new Thread(new Runnable() {
public void run() {
new DisplayServer(80);
}
}).start();
}
For more info read the article about Concurrency in Swing
So, I've been messing around with the Swing Timer in Java, trying to make a little time counter. However, the actionperformed method doesn't seem to react whenever I make a timer and let it run.
Here's my simplified UI class:
public class UI implements ActionListener {
private int value = 0;
Timer timer = new Timer(5,this);
#Override
public void actionPerformed(ActionEvent e) {
value++;
System.out.println(value);
}
public void start() {
timer.start();
}
}
And this is what my launcher looks like:
public class Launcher {
public static void main(String[] args) {
UI ui = new UI();
ui.start();
}
}
When I run the launcher, nothing happens. I do know he creates the UI and lets the timer start, but the timer doesn't seem to call the Actionperformed method.
I'm wondering why.
It should show the value +1 every interval of 5 (miliseconds?).
Thanks in advance!
Your program is exiting before the timer Thread has a chance to start. You should give a little time before exiting the main Thread to allow the timer Thread to keep running. Thread.sleep(100) after ui.start()should solve.
hey i can help you out... you should do the following ;
firstly import the following ;
import java.awt.event.ActionEvent ;
import java.awt.event.ActionListener ;
import javax.swing.Timer ;
then initialize the timer at the end of the form like this ;
public static void main(String args[]) {
java.awt.EventQueue.invokeLater(new Runnable() {
public void run() {
new mainprogramme().setVisible(true);
}
});
}
private Timer timer ;
then after initializing the timer add a public class like following;
public class progress implements ActionListener {
public void actionPerformed(ActionEvent evt){
int n = 0 ;
if (n<100){
n++ ;
System.out.println(n) ;
}else{
timer.stop() ;
}
}
}
after you do this go to the j Frame>right click and select>Events>window>window Opened and type the following ;
private void formWindowOpened(java.awt.event.WindowEvent evt) {
timer = new Timer(100,new progress()) ;
and after you do all this take a button name it as anything and type the following in its void like following ;
timer.start();
AND THAT'S IT CODE IT AND THEN REPLY ME...
I have been trying this all day in different variations with little success. Could someone please help explain what I am doing wrong? I am just a beginner with regards to threads.
private JTextArea text = new JTextArea();
private JButton button = new JButton("Cancel");
public StatusFrame() {
text.setEditable(false);
this.add(text);
this.add(button, BorderLayout.EAST);
this.setSize(new Dimension(150, 100));
this.setVisible(true);
}
public void updateStatus(String textIn) {
text.setText(textIn);
}
public JButton getButton() {
return button;
}
In another class, I am calling methods which may take a while to complete. I want to be able to call the StatusFrame.updateStatus() method to keep the user informed on the progress.
This is what I have:
someMethod() {
// prevent GUI from freezing using threads
final Runnable r = new Runnable() {
public void run() {
status = new StatusFrame();
}
};
SwingUtilities.invokeLater(r);
//do something
status.update("process 1 completed");
//do something else
status.updateStatus("Process 2 completed");
}
The frame appears but none of the code after the runnable appears to be run/processed. It just stops/blocks/something. But the GUI remains active
Thanks for any advice.
P.S.: I have tried using invokeAndWait() method but again not sure if I am doing it the right way. For now a quick fix would be preferred as I have not learned much about threads yet. Any instructions are welcome.
You have the concepts backwards.
Here's your code
someMethod() {
// prevent GUI from freezing using threads
final Runnable r = new Runnable() {
public void run() {
status = new StatusFrame();
}
};
SwingUtilities.invokeLater(r);
//do something
status.update("process 1 completed");
//do something else
status.updateStatus("Process 2 completed");
You should execute the long running code in a thread, and use the SwingUtilities invokeLater method to update the GUI.
someMethod() {
// prevent GUI from freezing using threads
final Runnable r = new Runnable() {
public void run() {
status = new StatusFrame();
}
};
new Thread(r).start();
// inside the StatusFrame
//do something
SwingUtilities.invokeLater(new Runnable() {
public void run() {
update("process 1 completed");
}
);
//do something else sometime later
SwingUtilities.invokeLater(new Runnable() {
public void run() {
update("Process 2 completed");
}
);
I don't know if I was clear in my answer.
Execute SwingUtilities.invokeLater when you start your Java application to make sure Swing components are on the Event Dispatch thread (EDT).
From the EDT, invoke long running processes as a runnable thread.
In the runnable thread, since you're not on the EDT, execute SwingUtilities.invokeLater whenever you're updating Swing components. This ensures that Swing components are updated on the EDT.
Every Swing application should start with a class like this:
import javax.swing.SwingUtilities;
import com.ggl.text.entry.model.TextEntryModel;
import com.ggl.text.entry.view.TextEntryFrame;
public class TextEntry implements Runnable {
#Override
public void run() {
new TextEntryFrame(new TextEntryModel());
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new TextEntry());
}
}
This class does 3 things.
Constructs the GUI data model.
Constructs the GUI JFrame.
Ensures that the Swing components are on the EDT.
You'll need to call the updates on EDT too. I would suggest to sleep on the main thread, to give GUI a chance to show up before any other work:
someMethod() {
// prevent GUI from freezing using threads
Runnable r = new Runnable() {
public void run() {
status = new StatusFrame();
}
};
SwingUtilities.invokeLater(r);
try {
Thread.sleep(10);
} catch (InterruptedException e) {
}
//do something
r = new Runnable() {
public void run() {
status.update("process 1 completed");
}
};
SwingUtilities.invokeLater(r);
//do something else
r = new Runnable() {
public void run() {
status.update("Process 2 completed");
}
};
SwingUtilities.invokeLater(r);
}
See Concurrency in Swing.
You may find using a Swing Worker easier to work with since it uses a Thread and has methods that will allow you to update the GUI properly.
I'm making an application with java swing. In a button of the application I need to every x minutes to make something.
I think that I must do it with a new thread, but I have two problems. The first is that I must to pass a parameter to these thread. I solved it with a class that extends of a Thread and a constructor. I think these way is correct no?
The second thing I cannot resolve it is that I need to update a jtextpane while the thread is running but if I try to update the JTextPane propierties Eclipse says me that cannot be resolved. I think that the problem is that these thread is not the main thread. But... there is some way to fix it?
Many thanks and sorry for my english!
The code is:
btnIniciar.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent arg0) {
//String file = "D:\\prueba.torrent";
// while (true) {
Hilo ejecutar = new Hilo(listaBuscar);
ejecutar.run();
public class Hilo extends Thread {
public Hilo(List<String> aBuscar){
}
public void run(){
System.out.println("Trabajo por hacer dentro de MiHilo");
java.awt.EventQueue.invokeLater(new Runnable() {
public void run() {
lblNewLabel.setText("hola");
}
});
}
}
It says me lblNewLabel cannot be resolved.
Any help?
Thanks
I'm trying with these code now and doesnt works:
public class Hilo implements Runnable {
private JLabel etiqueta;
public Hilo (List <String> aBuscar, JLabel label){
System.out.println("Hemos entrado en el puto hilo");
etiqueta = label;
}
#Override
public void run() {
etiqueta.setText("hola");
System.out.println("vamos a coneseguirlo");
// TODO Auto-generated method stub
SwingUtilities.invokeLater(new Runnable() {
public void run() {
etiqueta.setText("hola");
System.out.println("vamos a coneseguirlo");
}
});
}
}
Use Swing timer. It is very much like invisible button that is pressed periodically in the given intervals. It will call your actionPerformed already in a Swing thread from where you can manipulate components (same as from the JButton ActionListener). Hence most likely you do not need to run your own threads for this task.
You mention JTextPane in your question title but only refer to JLabel?
The main problem though you are having I see is that you have not declared the JLabel within the scope of your Thread, you could pass your JLabel instance which has a method to get a reference to the JLabel to your Thread via a constructor thus it has a reference to the JLabel, right now it doesnt.
Also I'd recommend using SwingUtilities and not EventQueue
And do not extend Thread class (unless adding custom functionality) rather implement a Runnable
Something like:
GUI.java:
public class GUI {
private JFrame frame;
private JLabel label;
private JButton btnIniciar;
public void getJLabel() {
return label;
}
public void initComponents() {
//create UI and components here
btnIniciar.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent arg0) {
//String file = "D:\\prueba.torrent";
Hilo ejecutar = new Hilo(listaBuscar,Gui.this);//pass reference of to our class
}
}
}
Hilo.java:
public class Hilo implements Runnable {
private Thread t;
private final GUI gui;
public Hilo(List<String> aBuscar, GUI ui){
this.gui=ui;
t=new Thread(this);
startThread();
}
#Override
public void run(){
SwingUtilities.invokeLater(new Runnable() {
public void run() {
gui.getJLabel().setText("hola");
}
});
}
//so we can start thread from other class
public void startThread() {
if(!t.isAlive()) //if the thread is not started alreade
t.start();
}
}
Though depending on what you are doing a Swing Timer might be what you need, it will allow you to run code, at intervals/delays and all this is done on the EDT already.
Bellow is the code for the simplest GUI countdown. Can the same be done in a shorter and more elegant way with the usage of the Swing timer?
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.SwingUtilities;
public class CountdownNew {
static JLabel label;
// Method which defines the appearance of the window.
public static void showGUI() {
JFrame frame = new JFrame("Simple Countdown");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
label = new JLabel("Some Text");
frame.add(label);
frame.pack();
frame.setVisible(true);
}
// Define a new thread in which the countdown is counting down.
public static Thread counter = new Thread() {
public void run() {
for (int i=10; i>0; i=i-1) {
updateGUI(i,label);
try {Thread.sleep(1000);} catch(InterruptedException e) {};
}
}
};
// A method which updates GUI (sets a new value of JLabel).
private static void updateGUI(final int i, final JLabel label) {
SwingUtilities.invokeLater(
new Runnable() {
public void run() {
label.setText("You have " + i + " seconds.");
}
}
);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
showGUI();
counter.start();
}
});
}
}
Yes you SHOULD use a Swing Timer. You SHOULD NOT, use a util Timer and TimerTask.
When a Swing Timer fires the code is executed on the EDT which means you just need to invoke the label.setText() method.
When using the uitl Timer and TimerTask, the code DOES NOT execute on the EDT, which means you need to wrap your code in a SwingUtilities.invokeLater to make sure the code executes on the EDT.
And that is way using a Swing Timer is shorter and more elegant than your current approach, it simplifies the coding because to code is executed on the EDT.
You could make it a little more elegant by using Timer with an appropriate TimerTask.
Yes, use a timer. updateGUI would be the code for the timer task, but it will need some changes as you won't be able to pass in i for each call since you just get a run() method.