I just had to write a test code for SWT threading test, and now stuck with Display.asyncExec() strange behavior.
addShellListener(new ShellAdapter() {
#Override
public void shellActivated(ShellEvent e) {
Display.getDefault().asyncExec(new Runnable(){
#Override
public void run() {
for(int i=0;i<1000;i++)
{
getLabel().setText(i+"");
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
});
}
});
I just run loopped Runnable with asyncExec on shell start, which updates label value inside the shell every second, simulating timer. Everything is okay and ticking until i try to drag the window. The window freezes on dragging (including "ticking" label) and notification "The program is not responding" appears, with exiting possible only by Java VM process killing.
I am not quite sure if I understand the use case, however in order to update the label every second, I recommend to wither spawn a background thread that triggers the label update every second or use timerExec() to do the update and schedule another timerExec() for the next update():
timerExec() variant
private class LabelUpdater implements Runnable {
#Override
public void run() {
if( !label.isDisposed() ) {
label.setText( ... );
label.getParent().layout();
display.timerExec( 1000, new LabelUpdater() );
}
}
}
shell.addListener( SWT.Activate, new Listener() {
#Override
public void handleEvent( Event event ) {
display.timerExec( 1000, new LabelUpdater() );
}
} );
Background Thread Variant
private class LabelUpdater implements Runnable {
#Override
public void run() {
if( !label.isDisposed() ) {
label.setText( ... );
label.getParent().layout();
}
}
}
Runnable runnable = new Runnable() {
#Override
public void run() {
while( !shell.isDisposed() ) {
display.asyncExec( new LabelUpdater() );
try {
Thread.sleep( 1000 );
} catch( InterruptedException ignore ) {
Thread.interrupted();
}
}
}
};
Thread thread = new Thread( runnable );
thread.setDaemon( true );
thread.start();
Note that the shell.isDisposed() check isn't thread-safe, but doesn't harm in practice because the LabelUpdater has to check if the widgets it updates are still alive anyway. (see here for a more detailed discussion.
The Runnable you give to Display.asyncExec is run in the SWT user interface thread. If you use Thread.sleep in this runnable the whole user interface will be blocked for the duration of the sleep so do not do this.
Instead of the sleep you can use
Display.getDefault().timerExec(1000, runnable);
to schedule a new runnable to be run 1000 milliseconds later.
Related
I have a method like below.
ProgressWindow is a sub class of JFrame containing JProgressBar.
addProgress() increments a value in the JProgressBar.
If I call this method from a method in another class, a frame of ProgressWindow will show up but not JProgressBar and some JLabels inside the frame. They show up after the last line (System.out.println("finish")).
If I call this method in a main method in the class containing this method, then every component (Bar, labels...) instantly shows up.
What can I do for showing the window correctly?
static void search(){
ProgressWindow window = new ProgressWindow();
window.setVisible(true);
ExecutorService execs = Executors.newFixedThreadPool(Runtime
.getRuntime().availableProcessors());
Collection<Callable<Void>> processes = new LinkedList<>();
for (int i = 0; i < 100; i++) {
processes.add(new Callable<Void>() {
#Override
public Void call() throws Exception {
progressWindow.addProgress(); // increment progress value
return null;
}
});
}
try {
execs.invokeAll(processes);
} catch (Exception e) {
e.printStackTrace();
} finally {
execs.shutdown();
}
System.out.println("finish");
The main problem is you seem to be calling search from the context of the Event Dispatching Thread.
The problem occurs because you are using execs.invokeAll which blocks until all the callables have finished running.
This means that the EDT is unable to process new events in Event Queue, including repaint events, this is why your UI is coming to a stand still...
There are a number of issues you are now going to face...
You should never update/modify a UI component from any thread other than the EDT
You should block the EDT for any reason
You seem to want to know when the search is complete, so you know need some kind of event notification...
The first thing we need is some way to be notified that the search has completed, this means you can no longer rely on search returning when the search is complete...
public interface SearchListener {
public void searchCompleted();
}
Next we need an intermeditate search method that builds the UI and ensure that the search is launched within it's own Thread...
static void search(final SearchListener listener) {
final ProgressWindow window = new ProgressWindow();
window.setVisible(true);
Thread t = new Thread(new Runnable() {
#Override
public void run() {
search(listener, window);
}
});
t.start();
}
Then we need to modify the original search method to utilise the SearchListener interface to provide notification when the search is complete...
static void search(final SearchListener listener, final ProgressWindow window){
ExecutorService execs = Executors.newFixedThreadPool(Runtime
.getRuntime().availableProcessors());
Collection<Callable<Void>> processes = new LinkedList<>();
for (int i = 0; i < 100; i++) {
processes.add(new Callable<Void>() {
#Override
public Void call() throws Exception {
// This method needs to ensure that
// what ever it does to the UI, it is done from within
// the context of the EDT!!
progressWindow.addProgress();
return null;
}
});
}
try {
execs.invokeAll(processes);
} catch (Exception e) {
e.printStackTrace();
} finally {
execs.shutdown();
}
System.out.println("finish");
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
listener.searchCompleted();
}
});
}
Now, without the source code for addProgress, I might be tempted to use
processes.add(new Callable<Void>() {
#Override
public Void call() throws Exception {
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
progressWindow.addProgress();
}
});
return null;
}
});
}
Instead...
Take a look at Concurrency in Swing for more details
Sounds like you what you're wanting to do is invoke the setVisible on the Swing UI thread, you can do this with invokeAndWait or invokeLater.
So something like:
final ProgressWindow window = new ProgressWindow();
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
window.setVisible(true);
}
});
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 am following a guide that shows how to create a Pong game. There is a part, where I am supposed to create a Thread, and call a function that moves the ball.
This is the code I created:
package com.ozadari.pingpong;
public class PingPongGame extends Thread {
private Ball gameBall;
private PingPongView gameView;
public PingPongGame(Ball theBall,PingPongView mainView)
{
this.gameBall = theBall;
this.gameView = mainView;
}
#Override
public void run()
{
while(true)
{
this.gameBall.moveBall();
this.gameView.postInvalidate();
try
{
PingPongGame.sleep(5);
}
catch(InterruptedException e)
{
e.printStackTrace();
}
}
}}
The thread is called and working, but it doesn't print anything. I tried to cancel the infinte loop and make the loop run 100 times. After I wait a while, it prints to the screen as it should be after 100 runs, but it doesn't print anything in the middle.
What is the problem? How can I fix it?
Unsure from the code you've posted but anyway, you can use a handler and have it run once every second like so (change the time to what you want):
Handler handler = new Handler();
final Runnable r = new Runnable()
{
public void run()
{
//do your stuff here
handler.postDelayed(this, 1000);
}
};
handler.postDelayed(r, 1000);
http://developer.android.com/reference/android/os/Handler.html
You can also use a normal thread, and call start at the end.
Thread thread = new Thread()
{
#Override
public void run() {
try {
while(true) {
sleep(1000);
handler.post(r);
}
} catch (InterruptedException e) {
e.printStackTrace();
}
}
};
thread.start();
In my GUI I have a PDF file creation operation. The operation can take up to 10-15 seconds to complete. When I start the operation, I attach a listener to it. The listener changes the cursor and disables the GUI, until the operation completes.
I would also like to add a progressbar, so the users will have a idea when it is going to complete.
Created a method startProgressBar() and called it from the start of the operation method.
See Below:
private void startSavePdfOperation() {
startProgressBar();
saveOp = new AplotSaveOperation(appReg.getString("aplot.message.SAVETOPDF"), "PDF", session);
saveOp.addOperationListener(new MyOperationListener(this) {
startProgressBar Method - See Below:
public void startProgressBar() {
Shell shell = new Shell(getShell());
shell.setSize(260, 120);
final ProgressBar bar = new ProgressBar(shell, SWT.SMOOTH);
bar.setBounds (20, 20, 200, 20);
shell.open();
final int maximum = bar.getMaximum();
new Thread(new Runnable() {
public void run() {
for (final int[] i = new int[1]; i[0] <= maximum; i[0]++) {
try {Thread.sleep (100);} catch (Throwable th) {}
if (Display.getDefault().isDisposed()) return;
Display.getDefault().asyncExec(new Runnable() {
public void run() {
if (bar.isDisposed ()) return;
bar.setSelection(i[0]);
}
});
}
}
}).start();
The code above created the ProgressBar. The issue is that the operation would end well before the progressbar indicator was close to ending.
Question: Is this because in the method I am creating a new thread and the indicator is updating according to the new thread and not the operation thread?
Question: Is it possible to create a new thread that watches the GUI thread and updates the progressbar accordingly?
Read a article suggesting using ProgressMonitorDialog with IRunnableWithProgress.
Method startProgressBar using ProgressMonitorDialog - see below:
public void startProgressBar() {
ProgressMonitorDialog dialog = new ProgressMonitorDialog(getShell());
try {
dialog.run(true, true, new IRunnableWithProgress(){
public void run(IProgressMonitor monitor) {
monitor.beginTask("Some nice progress message here ...", 100);
** getThread(); **
monitor.done();
}
});
}
catch (InvocationTargetException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
public void getThread() {
new Thread etc.. etc...
}
It seems that it will have the same issues with threading and updating as the code above.
Question: So now I am thinking can I just add or update the ProgressBar to my existing Listener
OperationListener Code - see below:
public abstract class MyOperationListener implements InterfaceAIFOperationListener {
AplotCreatePDFDialog w = null;
public MyOperationListener(AplotCreatePDFDialog win) {
w = win;
}
public void startOperation(String startMessage) {
Display.getDefault().asyncExec(new Runnable() {
public void run() {
w.getShell().setCursor(new Cursor(Display.getCurrent(), SWT.CURSOR_WAIT));
w.recursiveSetEnabled(getShell(), getShell().getEnabled());
w.getShell().setEnabled(!getShell().getEnabled());
}
});
}
public void endOperation() {
try {
endOperationImpl();
}
finally {
Display.getDefault().asyncExec(new Runnable() {
public void run() {
w.getShell().setCursor(new Cursor(Display.getCurrent(), SWT.CURSOR_ARROW));
w.recursiveSetEnabled(getShell(), true);
w.getShell().setEnabled(!getShell().getEnabled());
w.close();
}
});
}
}
abstract protected void endOperationImpl();
} // end class MyOperationListener
Thanks for any help you can give me with this.
EDIT
Baz, your answer below is exactly what the question asked, so thank you for answering.
But I am starting to think that what I am trying to do is not possible.
When my operation starts, I wanted the progress bar indicator to start and when my operation ended I wanted the indicator be at the end and the monitor would close.
I thought there might bee a way to use my listener to add the progressbar. Something like the following.
public void startOperation(String startMessage) {
Display.getDefault().asyncExec(new Runnable() {
public void run() {
->monitor.beginTask("Creating PDF File(s)", IProgressMonitor.UNKNOWN);<-
w.getShell().setCursor(new Cursor(Display.getCurrent(), SWT.CURSOR_WAIT));
w.recursiveSetEnabled(getShell(), getShell().getEnabled());
w.getShell().setEnabled(!getShell().getEnabled());
}
});
}
public void endOperation() {
try {
->monitor.worked(1);<-
endOperationImpl();
}
finally {
Display.getDefault().asyncExec(new Runnable() {
public void run() {
w.getShell().setCursor(new Cursor(Display.getCurrent(), SWT.CURSOR_ARROW));
w.recursiveSetEnabled(getShell(), true);
w.getShell().setEnabled(!getShell().getEnabled());
->monitor.done();<-
w.close();
}
});
}
}
abstract protected void endOperationImpl();
} // end class MyOperationListener
But I am starting to see that the ProgressBar has to have some sort of measurement to display the indicator correctly.
I would be happy if the indicator just went back and forth and the monitor would close at the end of the operation.
Why not use ProgressMonitorDialog?
Here is a related answer from me showing a simple example.
This is what it looks like:
If you are not sure about the workload, use this code:
monitor.beginTask("Copying files", IProgressMonitor.UNKNOWN);
It will show the idle bar while running.
In the following lines of code when Button1 is pressed the Jframe becomes unresponsive till the execution of the encode() method is completed. But I need to update a progress bar in the Jframe displaying the progress.
private void Button1ActionPerformed(java.awt.event.ActionEvent evt) {
try {
if (flagState == 0) {
WavFile.decode(readWavFile, msg.getText(), key.getText().hashCode());
} else if (flagState == 1) {
WavFile.encode(readWavFile, msg.getText(), key.getText().hashCode());
}
} catch (WavFileException | IOException e) {
notes.setText(e.getMessage());
}
}
I thought of doing this
private void Button1ActionPerformed(java.awt.event.ActionEvent evt) {
try {
if (flagState == 0) {
Thread t = new Thread(new Runnable() {
public void run() {
WavFile.decode(readWavFile, msg.getText(), key.getText().hashCode());
}
};)
t.start();
} else if (flagState == 1) {
Thread t = new Thread(new Runnable() {
public void run() {
WavFile.encode(readWavFile, msg.getText(), key.getText().hashCode());
}
};)
t.start();
}
} catch (WavFileException | IOException e) {
notes.setText(e.getMessage());
}
}
and update the progress bar from the encode() method.
But I understand that it will a strong coupling between the modules and i dont want that.
I also dont think that calling a new thread every time is a good idea ( thought of ExecutorService but not sure how to use it).
What should I do to make this into a decent piece code??
Threading is definitely something you have to introduce here. Anything that takes a significant amount of time to complete should not be run in the awt event thread.
Spawning a new thread each time the button is clicked is not inherently a problem. You should consider, though, that it may be possible to spawn many threads doing the same thing before even the first completes. You could use an Executor if you want, but it probably is not necessary.
As for tracking progress, I would add another thread that periodically queries the other thread and updates the progress bar as necessary. Here's how I would structure it:
private void Button1ActionPerformed(java.awt.event.ActionEvent evt) {
disableButton1();
final Thread t;
if (flagState == 0) {
t = new Thread(new Runnable() {
public void run() {
try {
WavFile.decode(readWavFile, msg.getText(), key.getText().hashCode());
} catch (WavFileException | IOException e) {
notes.setText(e.getMessage());
}
}
});
} else if (flagState == 1) {
t = new Thread(new Runnable() {
public void run() {
try {
WavFile.encode(readWavFile, msg.getText(), key.getText().hashCode());
} catch (WavFileException | IOException e) {
notes.setText(e.getMessage());
}
}
});
}
Thread monitor = new Thread(new Runnable() {
public void run() {
try {
while (notComplete(t)) {
setProgressBar(getProgress(t));
Thread.sleep(SLEEP_TIME);
}
t.join();
} finally {
enableButton1();
}
}
});
t.start();
monitor.start();
}
n the following lines of code when Button1 is pressed the Jframe becomes unresponsive till the execution of the encode() method is completed. But I need to update a progress bar in the Jframe displaying the progress.
you have issue with Concurency in Swing, you block the EDT, caused unresponsive GUI, until code ended
have look at SwingWorker for JProgressBar
use most scallable Swing Action instread of ActionListener
use implemented setEnabled() instead of if (flagState == 0) {
Multithreading is what you need, there is no other nice way i can think of don't worry about calling new threads, that's what they are there for, jvm has a thread pool ready to be used, this sort of things runs really good with threads, try it out!
Create a class that extends Runnable, implement the run method or make it call your current method, that should be enough to do this.
Also you could just make it sleep for a short time and check the status each time the sleep time goes out, if the process finished you can continue, if not, back to sleep for another short time, that way you don't have to ask that many times.
I hope it helps.