Develop Reference

JTextArea not displaying data from another class (minimal reproductile code for testing) [duplicate]

I originally was attempting to update a JFrame and JPanel several times while in a Java Action Listener, but both would only update when the Action Listener completed all its tasks. Here is the link to my original question (Refreshing a JFrame while in an Action Listener).
I was told in the feedback to that question that Swing Worker should solve my problems. However, when I implemented Swing Worker (as seen below), nothing changed. The JFrame and JPanel still updated only when the Action Listener completed all tasks. My question is, am I missing something below? If not, how can I implement this in an Action Listener to properly update the Frame and Panel timely?
#Override
protected Integer doInBackground() throws Exception{
//Downloads and unzips the first video.
if(cameraBoolean==true)
panel.add(this.downloadRecording(camera, recording));
else
panel.add(new JLabel("Could not contact camera "+camera.getName()));
panel.repaint();
jframe.repaint();
return 1;
}
private JLabel downloadRecording(Camera camera, Recording recording){
//does a bunch of calculations and returns a jLabel, and works correctly
}
protected void done(){
try{
Date currentTime = new Timestamp(Calendar.getInstance().getTime().getTime());
JOptionPane.showMessageDialog(jframe, "Camera "+camera.getName()+" finished downloading at "+currentTime.getTime());
}catch (Exception e){
e.printStackTrace();
}
}

You have a misundertanding about how SwingWorker works. This class is intended to provide a way to update the GUI while heavy tasks are being performed. All of this is because Swing components updates take place in the Event Dispatch Thread (a.k.a. EDT) which is a particular thread.
For instance, if you click a button and perform a time consuming task all in the EDT, then this thread will block untill this task finishes. Consequently, you'll see your GUI is frozen.
Keeping this in mind, doInBackground() method runs in another different thread that's not the EDT which is ok. So don't call any Swing method in there:
protected Integer doInBackground() throws Exception{
//Downloads and unzips the first video.
if(cameraBoolean==true) // just use if(cameraBoolean), since this is a boolean
panel.add(this.downloadRecording(camera, recording)); // NO!
else
panel.add(new JLabel("Could not contact camera "+camera.getName())); //NO!
panel.repaint(); //NO, never!
jframe.repaint();//NO, never!
return 1;
}
Add a JLabel to this panel before executing your SwingWorker and update its text using publish() and process() methods instead:
JPanel panel = new JPanel();
final JLabel progressLabel = new JLabel("Some text before executing SwingWorker");
panel.add(progressLabel);
SwingWorker<Integer, String> worker = new SwingWorker<Integer, String>() {
#Override
protected Integer doInBackground() throws Exception {
if(cameraBoolean){
pubish("Starting long process...");
//Some processing here
publish("Intermediate result to be published #1");
//Some other processing stuff
publish("Intermediate result to be published #2");
//And so on...
return 0;
} else {
publish("Could not contact camera "+camera.getName());
return -1;
}
}
#Override
protected void process(List<String> chunks) {
for(String string : chunks){
progressLabel.setText(string);
}
}
#Override
protected void done() {
progressLabel.setText("Finished!!!");
}
};
worker.execute();
Both process() and done() methods take place in the EDT so it's safe make GUI updates there. Take a look to this excelent example: Swing Worker Example for more details.

Maybe because you repaint your panel/frame just when the synchronous call this.downloadRecording(camera, recording) is finished?
Try to only put this call into the doInBackground() method, because (so I guess) that's the one that takes a long time and for all this time the JFrame gets not refreshed.

You can't update UI in next way:
panel.repaint();
jframe.repaint();
In your doInBackground method you must to call publish(V... chunks) method, that Sends data chunks to the process(java.util.List<V>) method.(according docs) and than in method process(List<V> chunks) you can update your UI(according docs process method - Receives data chunks from the publish method asynchronously on the Event Dispatch Thread.). SwingWorker docs.
So, override process method for updating, and call publish method.
Also you can use Executors for background processes. In this case your UI will be working in EDT and your background process in another thread. Example:
Executors.newSingleThreadExecutor().execute(new Runnable() {
#Override
public void run() {
// run background process
}
});
EDIT: good example of SwingWorker

Pause between images in Java [duplicate]

I have an array of strings which I'm trying to display (one by one) as a slideshow in a Java Swing component. I am also trying to add a delay time between the iterations.
I attempted to do this by using a JTextArea, with an action listener added to it. Here is the code I have right now:
private class myActionListener implements ActionListener {
public void actionPerformed(ActionEvent e) {
// A BUNCH OF TEXT PROCESSING
//NOTE: myInfo.getContents() returns an ArrayList<myType>.
Iterator<myType> iterator = myInfo.getContents().iterator();
int i = 0;
while (iterator.hasNext()) {
myTextArea.setText(iterator.next().toString());
// to add time betweeen iterations i wanted to use the thread
// delay method.
}
}
}
My code is not working because JTextArea doesn't have an action listener.
UPDATE
NOTE: Many replies stated that I should use an ActionListener for the JTextArea; However, Eclipse is not showing me that JTextArea has a method called addActionListener.
I'm kind of stuck here, which Java Swing component do you think would be the most suitable in this scenario?
The text in my array may be long, so a one lined label would not be a good choice.
What other alternatives or approaches do I have?
Thank you very much, any help and suggestions are appreciated.

This is basic example is based on the suggestion posted by #Robin
public class TestDisplayString {
public static void main(String[] args) {
new TestDisplayString();
}
public TestDisplayString() {
EventQueue.invokeLater(new Runnable() {
#Override
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (ClassNotFoundException ex) {
} catch (InstantiationException ex) {
} catch (IllegalAccessException ex) {
} catch (UnsupportedLookAndFeelException ex) {
}
JFrame frame = new JFrame("Test");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setLayout(new BorderLayout());
frame.add(new TestPane());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
public class TestPane extends JPanel {
private JTextArea textArea;
private List<String> content;
private Iterator<String> iterator;
public TestPane() {
readText();
setLayout(new BorderLayout());
textArea = new JTextArea(10, 40);
textArea.setLineWrap(true);
textArea.setWrapStyleWord(true);
add(new JScrollPane(textArea));
iterator = content.iterator();
Timer timer = new Timer(1000, new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
if (iterator.hasNext()) {
textArea.setText(iterator.next());
} else {
((Timer)e.getSource()).stop();
}
}
});
timer.setRepeats(true);
timer.setCoalesce(true);
timer.start();
}
protected void readText() {
content = new ArrayList<>(25);
BufferedReader reader = null;
try {
reader = new BufferedReader(new InputStreamReader(getClass().getResourceAsStream("/Text.txt")));
String text = null;
while ((text = reader.readLine()) != null) {
if (text.trim().length() > 0) {
content.add(text);
}
}
} catch (Exception e) {
e.printStackTrace();
} finally {
try {
reader.close();
} catch (Exception e) {
}
}
}
}
}
This is the contents of the "Text.txt" file.
How to Use Swing Timers
A Swing timer (an instance of javax.swing.Timer) fires one or more
action events after a specified delay. Don't confuse Swing timers with
the general-purpose timer facility that was added to the java.util
package in release 1.3. This page describes only Swing timers.
In general, we recommend using Swing timers rather than
general-purpose timers for GUI-related tasks because Swing timers all
share the same, pre-existing timer thread and the GUI-related task
automatically executes on the event-dispatch thread. However, you
might use a general-purpose timer if you don't plan on touching the
GUI from the timer, or need to perform lengthy processing.
You can use Swing timers in two ways:
To perform a task once, after a delay.
For example, the tool tip manager uses Swing timers to determine when to show a tool tip and when to hide it.
To perform a task repeatedly.
For example, you might perform animation or update a component that displays progress toward a goal.
Swing timers are very easy to use. When you create the timer, you
specify an action listener to be notified when the timer "goes off".
The actionPerformed method in this listener should contain the code
for whatever task you need to be performed. When you create the timer,
you also specify the number of milliseconds between timer firings. If
you want the timer to go off only once, you can invoke
setRepeats(false) on the timer. To start the timer, call its start
method. To suspend it, call stop.
Note that the Swing timer's task is performed in the event dispatch
thread. This means that the task can safely manipulate components, but
it also means that the task should execute quickly. If the task might
take a while to execute, then consider using a SwingWorker instead of
or in addition to the timer. See Concurrency in Swing for instructions
about using the SwingWorker class and information on using Swing
components in multi-threaded programs.
Let's look at an example of using a timer to periodically update a
component. The TumbleItem applet uses a timer to update its display at
regular intervals. (To see this applet running, go to How to Make
Applets. This applet begins by creating and starting a timer:
timer = new Timer(speed, this); timer.setInitialDelay(pause);
timer.start();
The speed and pause variables represent applet parameters; as
configured on the other page, these are 100 and 1900 respectively, so
that the first timer event will occur in approximately 1.9 seconds,
and recur every 0.1 seconds. By specifying this as the second argument
to the Timer constructor, TumbleItem specifies that it is the action
listener for timer events.
After starting the timer, TumbleItem begins loading a series of images
in a background thread. Meanwhile, the timer events begin to occur,
causing the actionPerformed method to execute:
public void actionPerformed(ActionEvent e) {
//If still loading, can't animate.
if (!worker.isDone()) {
return;
}
loopslot++;
if (loopslot >= nimgs) {
loopslot = 0;
off += offset;
if (off < 0) {
off = width - maxWidth;
} else if (off + maxWidth > width) {
off = 0;
}
}
animator.repaint();
if (loopslot == nimgs - 1) {
timer.restart();
} }
Until the images are loaded, worker.isDone returns false, so timer
events are effectively ignored. The first part of the event handling
code simply sets values that are employed in the animation control's
paintComponent method: loopslot (the index of the next graphic in the
animation) and off (the horizontal offset of the next graphic).
Eventually, loopslot will reach the end of the image array and start
over. When this happens, the code at the end of actionPerformed
restarts the timer. Doing this causes a short delay before the
animation sequence begins again.

Use your ActionListener in combination with a javax.Swing.Timer. The ActionListener assigned to the Timer will be called on regular intervals with the specified delay.
See the timer tutorial for more information

Disable parent frame without stopping thread?

I'm developing a Swing app, and I need to run an infinite loop in the background (which runs until: 1) the cancel button of my JDialog is selected or 2) the input data it is searching for is found) while a modal dialog shows an indeterminate progress bar.
Something I've noticed is that if the JDialog is modal, then the SwingWorker will not execute its tasks until the JDialog is closed (and releases its deathgrip on the EDT, I guess...?). If the JDialog is not modal, then SwingWorker's tasks will execute happily in the background.
I've been doing some research, but I'm no thread/EDT expert and am having a hard time figuring the reason/solution.
Any input on this situation/threads/EDT/SwingWorker, or a suggested solution, would be greatly appreciated.
(Question pulled directly from: http://www.coderanch.com/t/346275/GUI/java/SwingWorker-Modal-JDialogs)
I tried the solution regarding the setVisible call of the JDialog like this user found to be the solution, but I still can't execute both threads simultaneously. Any help would be appreciated.
Relevant:
public Dialog(JFrame parentFrame, String equipmentName) {
super(parentFrame, "Progress");
this.hasRequestedCancel = false;
this.equipmentName = equipmentName;
add(createMainPanel());
setIconImage(Toolkit.getDefaultToolkit().getImage(SomeClass.class.getResource(ICON_PATH)));
setDefaultCloseOperation(WindowConstants.DO_NOTHING_ON_CLOSE);
setModalityType(ModalityType.DOCUMENT_MODAL);
pack();
setSize(550, 100);
setResizable(false);
setLocationRelativeTo(parentFrame);
setVisible(true);
}
And
SwingWorker<File, Void> worker = createSwingWorker(params, ...);
worker.execute();
And
private SwingWorker<File, Void> createSwingWorker(final File someFile, final SomeClass asdf, final String param3) throws IOException {
SwingWorker<File, Void> swingWorker = new SwingWorker<File, Void>() {
#Override
protected File doInBackground() throws IOException {
Dialog progressBar = new Dialog(SomeClass.this, SomeClass.this.equipManufacturerDevice);
try {
while(!someFile.exists() && !progressBar.hasRequestedCancel()) {
Thread.sleep(SomeClass.SLEEP_DURATION);
System.out.println("yo");
}
} catch (InterruptedException e) {
}
...
}
#Override
protected void done() {
...
}
};
return swingWorker;
}

The problem is that you are calling setVisible(true) inside the Dialog’s constructor which is a discouraged practice anyway (you just found one reason, why).
Separate the creation and opening of the dialog and you don’t have that problem anymore. The following sample code demonstrates how this can be achieved:
final Dialog d=new Dialog((Window)null);
d.setSize(300, 300);
d.setModal(true);
new SwingWorker<Object,Object>() {
#Override
protected Object doInBackground() throws Exception {
System.out.println("long running stuff");
TimeUnit.SECONDS.sleep(10);
System.out.println("end of long running stuff");
return null;
}
#Override
protected void done() {
d.dispose();
}
}.execute();
System.out.println("before setVisible(true)");
d.setVisible(true);// will block
System.out.println("after setVisible(true)");

What if you moved the data input logic from the main frame and kept it running on a separate, dedicated, background thread whose sole job is to listen for connections and handle them. This would leave your parent JFrame to handle UI interactions thereby giving you the freedom to freeze it when one of your JDialog has focus.

Java and SWT: Threads and Listeners

I'm actually new to Java and SWT, so my question might sound dumb.
I've looked over the intrnet (and stackoverflow) but all the answers and examples are too complex for a noob like me.
I have a class, call it Admin. When I click a button, it launches a method in another class(Handler).
In Admin I have a progress bar, that should increase with the
operation in Handler.
I don't know how much time the operations in
Handler takes, but I know I have 9 of them.
I would like, somehow,
to inform Admin when each method has finished.
What I have so far: (non relevant parts omitted)
Admin.java:
ProgressBar bar = new ProgressBar(this, SWT.SMOOTH);
Button btn = new Button(this, SWT.NONE);
btn.setText("Update");
btn.addListener(SWT.Selection, new Listener() {
public void handleEvent(Event event) {
btn.setEnabled(false);
thread.start();
}
});
Handler handler = new Handler();
final Thread thread = new Thread(){
public void run() {
handler.run();
for(int i=0; i<=10; i++) {
final int value = i;
try {
Thread.sleep(800);
} catch (Exception e) { }
display.asyncExec(new Runnable(){
public void run() {
bar.setSelection(value);
}
});
}
}
};
Handler.java:
public class Handler implements Runnable{
void m1() {...}
void m2() {...}
...
void m9() {...}
public void run()
{
m1();
m2();
...
m9();
}
With this implementation, the call to handler.run() works fine, and the progress bar is filling, but of course they are not "corelated" in any way.
I will appreciate your wisdom!
Thank you very much!

The highly coupled way of solving this, is to have the Handler take a ProgressBar as input in the constructor, and after m1() finishes, it updates the progress to 1/9 and so on. A better (more decoupled) way to do it, is that you can "listen" to Handler, and that Handler fires an event with its progress after each method finishes. Then you can update in the Admin.java.

I will ask you to consider using ProgressMonitorDialog from JFace if adding this library to your application is not much of a problem. Your code then would look something like below:
ProgressMonitorDialog dialog = new ProgressMonitorDialog(parent);
dialog.run(true, true, new IRunnableWithProgress() {
#Override
public void run(IProgressMonitor monitor) throws InvocationTargetException,
InterruptedException {
monitor.beginTask("my work", 9);
m1();
monitor.worked(1);
m2();
monitor.worked(1);
...
m9();
monitor.done;
}
});
You can also send the monitor instance into your m* methods for even detailed reporting. Have a look at SubProgressMonitor for dividing each one of your initial 9 ticks further before sending them into each m* method.
But this means that your progress bar is a new dialog which might not be acceptable to you so in that case the first answer suits your needs.

Displaying contents of String array in Swing component as iterations using Time delay. JAVA

I have an array of strings which I'm trying to display (one by one) as a slideshow in a Java Swing component. I am also trying to add a delay time between the iterations.
I attempted to do this by using a JTextArea, with an action listener added to it. Here is the code I have right now:
private class myActionListener implements ActionListener {
public void actionPerformed(ActionEvent e) {
// A BUNCH OF TEXT PROCESSING
//NOTE: myInfo.getContents() returns an ArrayList<myType>.
Iterator<myType> iterator = myInfo.getContents().iterator();
int i = 0;
while (iterator.hasNext()) {
myTextArea.setText(iterator.next().toString());
// to add time betweeen iterations i wanted to use the thread
// delay method.
}
}
}
My code is not working because JTextArea doesn't have an action listener.
UPDATE
NOTE: Many replies stated that I should use an ActionListener for the JTextArea; However, Eclipse is not showing me that JTextArea has a method called addActionListener.
I'm kind of stuck here, which Java Swing component do you think would be the most suitable in this scenario?
The text in my array may be long, so a one lined label would not be a good choice.
What other alternatives or approaches do I have?
Thank you very much, any help and suggestions are appreciated.

This is basic example is based on the suggestion posted by #Robin
public class TestDisplayString {
public static void main(String[] args) {
new TestDisplayString();
}
public TestDisplayString() {
EventQueue.invokeLater(new Runnable() {
#Override
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (ClassNotFoundException ex) {
} catch (InstantiationException ex) {
} catch (IllegalAccessException ex) {
} catch (UnsupportedLookAndFeelException ex) {
}
JFrame frame = new JFrame("Test");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setLayout(new BorderLayout());
frame.add(new TestPane());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
public class TestPane extends JPanel {
private JTextArea textArea;
private List<String> content;
private Iterator<String> iterator;
public TestPane() {
readText();
setLayout(new BorderLayout());
textArea = new JTextArea(10, 40);
textArea.setLineWrap(true);
textArea.setWrapStyleWord(true);
add(new JScrollPane(textArea));
iterator = content.iterator();
Timer timer = new Timer(1000, new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
if (iterator.hasNext()) {
textArea.setText(iterator.next());
} else {
((Timer)e.getSource()).stop();
}
}
});
timer.setRepeats(true);
timer.setCoalesce(true);
timer.start();
}
protected void readText() {
content = new ArrayList<>(25);
BufferedReader reader = null;
try {
reader = new BufferedReader(new InputStreamReader(getClass().getResourceAsStream("/Text.txt")));
String text = null;
while ((text = reader.readLine()) != null) {
if (text.trim().length() > 0) {
content.add(text);
}
}
} catch (Exception e) {
e.printStackTrace();
} finally {
try {
reader.close();
} catch (Exception e) {
}
}
}
}
}
This is the contents of the "Text.txt" file.
How to Use Swing Timers
A Swing timer (an instance of javax.swing.Timer) fires one or more
action events after a specified delay. Don't confuse Swing timers with
the general-purpose timer facility that was added to the java.util
package in release 1.3. This page describes only Swing timers.
In general, we recommend using Swing timers rather than
general-purpose timers for GUI-related tasks because Swing timers all
share the same, pre-existing timer thread and the GUI-related task
automatically executes on the event-dispatch thread. However, you
might use a general-purpose timer if you don't plan on touching the
GUI from the timer, or need to perform lengthy processing.
You can use Swing timers in two ways:
To perform a task once, after a delay.
For example, the tool tip manager uses Swing timers to determine when to show a tool tip and when to hide it.
To perform a task repeatedly.
For example, you might perform animation or update a component that displays progress toward a goal.
Swing timers are very easy to use. When you create the timer, you
specify an action listener to be notified when the timer "goes off".
The actionPerformed method in this listener should contain the code
for whatever task you need to be performed. When you create the timer,
you also specify the number of milliseconds between timer firings. If
you want the timer to go off only once, you can invoke
setRepeats(false) on the timer. To start the timer, call its start
method. To suspend it, call stop.
Note that the Swing timer's task is performed in the event dispatch
thread. This means that the task can safely manipulate components, but
it also means that the task should execute quickly. If the task might
take a while to execute, then consider using a SwingWorker instead of
or in addition to the timer. See Concurrency in Swing for instructions
about using the SwingWorker class and information on using Swing
components in multi-threaded programs.
Let's look at an example of using a timer to periodically update a
component. The TumbleItem applet uses a timer to update its display at
regular intervals. (To see this applet running, go to How to Make
Applets. This applet begins by creating and starting a timer:
timer = new Timer(speed, this); timer.setInitialDelay(pause);
timer.start();
The speed and pause variables represent applet parameters; as
configured on the other page, these are 100 and 1900 respectively, so
that the first timer event will occur in approximately 1.9 seconds,
and recur every 0.1 seconds. By specifying this as the second argument
to the Timer constructor, TumbleItem specifies that it is the action
listener for timer events.
After starting the timer, TumbleItem begins loading a series of images
in a background thread. Meanwhile, the timer events begin to occur,
causing the actionPerformed method to execute:
public void actionPerformed(ActionEvent e) {
//If still loading, can't animate.
if (!worker.isDone()) {
return;
}
loopslot++;
if (loopslot >= nimgs) {
loopslot = 0;
off += offset;
if (off < 0) {
off = width - maxWidth;
} else if (off + maxWidth > width) {
off = 0;
}
}
animator.repaint();
if (loopslot == nimgs - 1) {
timer.restart();
} }
Until the images are loaded, worker.isDone returns false, so timer
events are effectively ignored. The first part of the event handling
code simply sets values that are employed in the animation control's
paintComponent method: loopslot (the index of the next graphic in the
animation) and off (the horizontal offset of the next graphic).
Eventually, loopslot will reach the end of the image array and start
over. When this happens, the code at the end of actionPerformed
restarts the timer. Doing this causes a short delay before the
animation sequence begins again.

Use your ActionListener in combination with a javax.Swing.Timer. The ActionListener assigned to the Timer will be called on regular intervals with the specified delay.
See the timer tutorial for more information