Can you get this SwingWorker code to work more than once


C

clusardi2k

From: (e-mail address removed)

Here is a project that works perfectly only the first time. This is what it
does on the first button press:

It starts-up with only a "Start" button.

(1) Pressing start displays "Hello World". (2) The three "for" loops are
executed in the code. (3) "Hello World" disappears.

But, when you press the "Start" button a second time this happens:

(1) Displays "Hello World",

How do you modify the below code so that the second button press matches the
first button press.

The code has a button and a label.

After answering the above question, another question that I have is: can you
make this code better in any way imaginable.

Thank you,

//Code:
package Test_SwingWorker;

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener; import java.beans.PropertyChangeEvent;
import java.beans.PropertyChangeListener; import java.util.List;
import javax.swing.SwingWorker;

public class Test_SwingWorker extends javax.swing.JFrame {
public Test_SwingWorker()
{
initComponents();

//The "Hello World" label that is not seen on Start-up
jLabel1.setVisible (false);

final Non_GUI_Stuff task = new Non_GUI_Stuff();

jButton1.addActionListener(new ActionListener()
{
public void actionPerformed(ActionEvent e)
{
//The "Hello World" label that appears when button is pressed
jLabel1.setVisible (true);

task.execute();
}
});
}

private void initComponents() {

jPanel1 = new javax.swing.JPanel();
jButton1 = new javax.swing.JButton();
jLabel1 = new javax.swing.JLabel();

setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);

jButton1.setText("Start");

jLabel1.setText("Hello World");

javax.swing.GroupLayout jPanel1Layout = new
javax.swing.GroupLayout(jPanel1);
jPanel1.setLayout(jPanel1Layout);
jPanel1Layout.setHorizontalGroup(
jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment
..LEADING)
.addGroup(jPanel1Layout.createSequentialGroup()
.addGap(167, 167, 167)
.addComponent(jButton1)
.addGap(51, 51, 51)
.addComponent(jLabel1)
.addContainerGap(55, Short.MAX_VALUE))
);
jPanel1Layout.setVerticalGroup(
jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment
..LEADING)
.addGroup(jPanel1Layout.createSequentialGroup()
.addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLa
yout.Alignment.LEADING)
.addComponent(jButton1)
.addGroup(jPanel1Layout.createSequentialGroup()
.addContainerGap()
.addComponent(jLabel1)))
.addContainerGap(283, Short.MAX_VALUE))
);

javax.swing.GroupLayout layout = new
javax.swing.GroupLayout(getContentPane());
getContentPane().setLayout(layout);
layout.setHorizontalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADIN
G)
.addComponent(jPanel1, javax.swing.GroupLayout.DEFAULT_SIZE,
javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
);
layout.setVerticalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADIN
G)
.addComponent(jPanel1, javax.swing.GroupLayout.DEFAULT_SIZE,
javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
);

pack();
}

public static void main(String args[])
{
java.awt.EventQueue.invokeLater(new Runnable()
{
public void run()
{
new Test_SwingWorker().setVisible(true);
}
});
}

class Non_GUI_Stuff extends SwingWorker<Integer, Integer> {
protected Integer doInBackground() throws Exception
{
//"for" loops mentioned above
for (int i = 0;i < 100000; i++)
for (int i2 = 0;i2 < 100000; i2++);
for (int i3 = 0;i3 < 100000; i3++);

return 0;
}

protected void done()
{
//The "Hello World" label that disappears
jLabel1.setVisible (false);
}
}

private javax.swing.JButton jButton1;
private javax.swing.JLabel jLabel1;
private javax.swing.JPanel jPanel1;
}

--- BBBS/Li6 v4.10 Dada-1
* Origin: Prism bbs (1:261/38)
--- Synchronet 3.16a-Win32 NewsLink 1.98
Time Warp of the Future BBS - telnet://time.synchro.net:24
 
Ad

Advertisements

E

Eric Sosman

To: clusardi2k
From: Eric Sosman <[email protected]>

Here is a project that works perfectly only the first time. [...]

Quoth the JavaDoc: "SwingWorker is only designed to be executed
once. Executing a SwingWorker more than once will not result in invoking the
doInBackground method twice." If you want to do a background task N times,
you'll need N instances of SwingWorker, one per task execution.

--
Eric Sosman
(e-mail address removed)

--- BBBS/Li6 v4.10 Dada-1
* Origin: Prism bbs (1:261/38)
--- Synchronet 3.16a-Win32 NewsLink 1.98
Time Warp of the Future BBS - telnet://time.synchro.net:24
 
C

clusardi2k

To: Eric Sosman
From: (e-mail address removed)

On 8/9/2012 11:24 AM, ... wrote: > Here is a project that works
perfectly only the first time. [...] Quoth the JavaDoc: "SwingWorker is only
designed to be executed once. Executing a SwingWorker more than once will not
result in invoking the doInBackground method twice." If you want to do a
background task N times, you'll need N instances of SwingWorker, one per task
execution. -- Eric Sosman (e-mail address removed)

So, I want a project to do the following:

(1) Display a button when the project is run, (2) When the user presses the
button, a label is displayed. (3) The project next executes three long "for"
loops such as in a previous post of this thread.
(4) When the three "for" loops are finished, the label disappears.

Question: How can I repeatedly do steps (2) through (4) above when a project is
started?

Thank you,

--- BBBS/Li6 v4.10 Dada-1
* Origin: Prism bbs (1:261/38)
--- Synchronet 3.16a-Win32 NewsLink 1.98
Time Warp of the Future BBS - telnet://time.synchro.net:24
 
C

clusardi2k

To: Eric Sosman
From: (e-mail address removed)

On 8/9/2012 11:24 AM, (e-mail address removed) wrote: > Here is a project that works
perfectly only the first time. [...] Quoth the JavaDoc: "SwingWorker is only
designed to be executed once. Executing a SwingWorker more than once will not
result in invoking the doInBackground method twice." If you want to do a
background task N times, you'll need N instances of SwingWorker, one per task
execution. -- Eric Sosman (e-mail address removed)

How do you modify the code my last post to do that.

Thank you,

--- BBBS/Li6 v4.10 Dada-1
* Origin: Prism bbs (1:261/38)
--- Synchronet 3.16a-Win32 NewsLink 1.98
Time Warp of the Future BBS - telnet://time.synchro.net:24
 
M

markspace

To: clusardi2k
From: markspace <[email protected]>

On 8/9/2012 11:24 AM, ... wrote: > Here is a project that works
perfectly only the first time. [...] Quoth the JavaDoc: "SwingWorker is only
designed to be executed once. Executing a SwingWorker more than once will not
result in invoking the doInBackground method twice." If you want to do a
background task N times, you'll need N instances of SwingWorker, one per task
execution. -- Eric Sosman (e-mail address removed)
So, I want a project to do the following:

(1) Display a button when the project is run,
(2) When the user presses the button, a label is displayed.
(3) The project next executes three long "for" loops such as in a previous post of this thread.
(4) When the three "for" loops are finished, the label disappears.

Question: How can I repeatedly do steps (2) through (4) above when a project
is started?


In this case just move the "new Non_GUI_Stuff()" inside the actionPreformed()
method. Then "new" will get executed each time the user presses the button,
you'll get a new object that you can execute with no problems.


jButton1.addActionListener(new ActionListener()
{
public void actionPerformed(ActionEvent e)
{
//The "Hello World" label that appears
//when button is pressed

Non_GUI_Stuff task = new Non_GUI_Stuff();

jLabel1.setVisible (true);

task.execute();
}
});


If all you really want to do is delay the label disappearing, use a Timer
instead of for-loops.

--- BBBS/Li6 v4.10 Dada-1
* Origin: Prism bbs (1:261/38)
--- Synchronet 3.16a-Win32 NewsLink 1.98
Time Warp of the Future BBS - telnet://time.synchro.net:24
 
K

Knute Johnson

To: clusardi2k
From: Knute Johnson <[email protected]>

Here is a project that works perfectly only the first time. This is what it
does on the first button press:
It starts-up with only a "Start" button.

(1) Pressing start displays "Hello World".
(2) The three "for" loops are executed in the code.
(3) "Hello World" disappears.

But, when you press the "Start" button a second time this happens:

(1) Displays "Hello World",

How do you modify the below code so that the second button press matches the first button press.

The code has a button and a label.

After answering the above question, another question that I have is: can you
make this code better in any way imaginable.
Thank you,

//Code:
package Test_SwingWorker;

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.beans.PropertyChangeEvent;
import java.beans.PropertyChangeListener;
import java.util.List;
import javax.swing.SwingWorker;

public class Test_SwingWorker extends javax.swing.JFrame
{
public Test_SwingWorker()
{
initComponents();

//The "Hello World" label that is not seen on Start-up
jLabel1.setVisible (false);

final Non_GUI_Stuff task = new Non_GUI_Stuff();

jButton1.addActionListener(new ActionListener()
{
public void actionPerformed(ActionEvent e)
{
//The "Hello World" label that appears when button is pressed
jLabel1.setVisible (true);

task.execute();
}
});
}

private void initComponents() {

jPanel1 = new javax.swing.JPanel();
jButton1 = new javax.swing.JButton();
jLabel1 = new javax.swing.JLabel();

setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);

jButton1.setText("Start");

jLabel1.setText("Hello World");

javax.swing.GroupLayout jPanel1Layout = new javax.swing.GroupLayout(jPanel1);
ent.LEADING)
.addGroup(jPanel1Layout.createSequentialGroup()
.addGap(167, 167, 167)
.addComponent(jButton1)
.addGap(51, 51, 51)
.addComponent(jLabel1)
.addContainerGap(55, Short.MAX_VALUE))
);
jPanel1Layout.setVerticalGroup(
jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignm ent.LEADING)
pLayout.Alignment.LEADING)
.addComponent(jButton1)
.addGroup(jPanel1Layout.createSequentialGroup()
.addContainerGap()
.addComponent(jLabel1)))
.addContainerGap(283, Short.MAX_VALUE))
);

javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
DING)
.addComponent(jPanel1, javax.swing.GroupLayout.DEFAULT_SIZE,
javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
);
layout.setVerticalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEA DING)
.addComponent(jPanel1, javax.swing.GroupLayout.DEFAULT_SIZE,
javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
);

pack();
}

public static void main(String args[])
{
java.awt.EventQueue.invokeLater(new Runnable()
{
public void run()
{
new Test_SwingWorker().setVisible(true);
}
});
}

class Non_GUI_Stuff extends SwingWorker<Integer, Integer>
{
protected Integer doInBackground() throws Exception
{
//"for" loops mentioned above
for (int i = 0;i < 100000; i++)
for (int i2 = 0;i2 < 100000; i2++);
for (int i3 = 0;i3 < 100000; i3++);

return 0;
}

protected void done()
{
//The "Hello World" label that disappears
jLabel1.setVisible (false);
}
}

private javax.swing.JButton jButton1;
private javax.swing.JLabel jLabel1;
private javax.swing.JPanel jPanel1;
}

Read the docs dude "SwingWorker is only designed to be executed once. Executing
a SwingWorker more than once will not result in invoking the doInBackground
method twice."

Just create a new SwingWorker Object and execute it again.

Your code is hard to follow and overly verbose. You could simplify it by
importing more classes. I would put the variable declarations at the top
somewhere, not because they don't work there but because it is where one would
expect to find it.

Below find some sample code for a very simple task, drawing in response to a
button press.

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class test extends JPanel implements ActionListener {
private String state = "";

public test() {
setPreferredSize(new Dimension(400,300));
}

public void actionPerformed(ActionEvent ae) {
state = ae.getActionCommand();
repaint();
}

public void paintComponent(Graphics g) {
g.setColor(getBackground());
g.fillRect(0,0,getWidth(),getHeight());
g.setColor(getForeground());
if (state.equals("Line"))
g.drawLine(0,0,getWidth(),getHeight());
else if (state.equals("Oval"))
g.drawOval(0,0,getWidth(),getHeight());
else if (state.equals("Rect"))
g.drawRect(5,5,getWidth()-10,getHeight()-10);
}

public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
public void run() {
test t = new test();
JFrame f = new JFrame("test");
f.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
f.add(t,BorderLayout.CENTER);
JPanel p = new JPanel();
JButton b = new JButton("Line");
b.addActionListener(t);
p.add(b);
b = new JButton("Oval");
b.addActionListener(t);
p.add(b);
b = new JButton("Rect");
b.addActionListener(t);
p.add(b);
f.add(p,BorderLayout.NORTH);
f.pack();
f.setVisible(true);
}
});
}
}

And a simplified example similar to what you were trying to do.

import java.awt.*;
import java.awt.event.*;
import java.util.concurrent.*;
import javax.swing.*;

public class test2 extends JPanel {
private final JLabel label;

private int count = 0;

public test2() {
super(new GridBagLayout());

setPreferredSize(new Dimension(320,240));

GridBagConstraints c = new GridBagConstraints();
c.insets = new Insets(2,2,2,2);

c.gridy = 0;
c.anchor = GridBagConstraints.NORTH;
JButton b = new JButton("Hello");
b.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent ae) {
(new DelayWorker()).execute();
}
});
add(b,c);

++c.gridy;
c.anchor = GridBagConstraints.CENTER;
c.weightx = c.weighty = 1.0;
label = new JLabel("");
add(label,c);
}

class DelayWorker extends SwingWorker<Integer,Object> {
public Integer doInBackground() throws InterruptedException {
++count;
Thread.sleep(1000);
return count;
}

public void done() {
try {
label.setText(get().toString());
} catch (InterruptedException ie) {
ie.printStackTrace();
} catch (ExecutionException ee) {
ee.printStackTrace();
}
}
}

public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
public void run() {
JFrame f = new JFrame("test2");
f.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
test2 t2 = new test2();
f.add(t2,BorderLayout.CENTER);
f.pack();
f.setVisible(true);
}
});
}
}



--

Knute Johnson

--- BBBS/Li6 v4.10 Dada-1
* Origin: Prism bbs (1:261/38)
--- Synchronet 3.16a-Win32 NewsLink 1.98
Time Warp of the Future BBS - telnet://time.synchro.net:24
 
Ad

Advertisements

E

Eric Sosman

To: clusardi2k
From: Eric Sosman <[email protected]>

On 8/9/2012 11:24 AM, ... wrote: > Here is a project that works
perfectly only the first time. [...] Quoth the JavaDoc: "SwingWorker is only
designed to be executed once. Executing a SwingWorker more than once will not
result in invoking the doInBackground method twice." If you want to do a
background task N times, you'll need N instances of SwingWorker, one per task
execution. -- Eric Sosman (e-mail address removed)

So, I want a project to do the following:

(1) Display a button when the project is run,
(2) When the user presses the button, a label is displayed.
(3) The project next executes three long "for" loops such as in a previous post of this thread.
(4) When the three "for" loops are finished, the label disappears.

Question: How can I repeatedly do steps (2) through (4) above when a project
is started?

"When a project is started?" Or "Each time the user presses
the button?" I'll assume the latter.

When you set up the button, create an ActionListener to be
notified of button presses. The listener's actionPerformed() method will
display the label (that's #2 above), create a SwingWorker, call the worker's
execute() method, and return.

Because execute() was called, Java will ("eventually," but in
practice "fairly soon") start the SwingWorker on a background thread and call
its doInBackground() method. This method runs the long loops (#3) and then
returns. Note that since it's executing on a background thread and not on the
event dispatch thread (EDT), doInBackground() should do almost nothing to or
with the GUI: Only a very few bits of Swing are thread-safe.

After doInBackground() returns, Java will ("eventually/soon")
call the SwingWorker's done() method. This call runs on the EDT, so the done()
method can manipulate the GUI: It can make the label invisible or even remove
it from its container (#4).

Next time the user presses the button, the actionPerformed()
method creates a brand-new SwingWorker and the same sequence of actions
repeats. You can't re-use the old SwingWorker instance, but you can create a
new instance of the same class, running the same code.

All this and more is covered in the Java Tutorial's chapter
on Swing concurrency,

<http://docs.oracle.com/javase/tutorial/uiswing/concurrency/worker.html>

--
Eric Sosman
(e-mail address removed)

--- BBBS/Li6 v4.10 Dada-1
* Origin: Prism bbs (1:261/38)
--- Synchronet 3.16a-Win32 NewsLink 1.98
Time Warp of the Future BBS - telnet://time.synchro.net:24
 
Ad

Advertisements

E

Eric Sosman

To: clusardi2k
From: Eric Sosman <[email protected]>

On 8/9/2012 11:24 AM, (e-mail address removed) wrote: > Here is a project that works
perfectly only the first time. [...] Quoth the JavaDoc: "SwingWorker is only
designed to be executed once. Executing a SwingWorker more than once will not
result in invoking the doInBackground method twice." If you want to do a
background task N times, you'll need N instances of SwingWorker, one per task
execution. -- Eric Sosman (e-mail address removed)

How do you modify the code my last post to do that.

Because there's a faint whiff of "homework assignment" about
your questions, *I* don't modify your code at all. *You* modify it along the
lines people have suggested, and post your new code if you're still having
trouble with it.

--
Eric Sosman
(e-mail address removed)

--- BBBS/Li6 v4.10 Dada-1
* Origin: Prism bbs (1:261/38)
--- Synchronet 3.16a-Win32 NewsLink 1.98
Time Warp of the Future BBS - telnet://time.synchro.net:24
 

Ask a Question

Want to reply to this thread or ask your own question?

You'll need to choose a username for the site, which only take a couple of moments. After that, you can post your question and our members will help you out.

Ask a Question

Top