Should I create swing elements into EDT?
I got the concurrency problems with editing non thread-safe graphics elements, but I'm creating them, they aren't shown yet, and if they are a lot or they take some time to be allocated that would freeze the GUI, doesn't it?
Here an example where I use EDT to display but not to create my GUI structure:
public class Launcher {
private final SwingWorker worker;
private final JFrame frame;
private final JLabel label;
private final JProgressBar progressBar;
public Launcher() {
// init user interface
frame = new JFrame();
JPanel panel = new JPanel(new BorderLayout());
label = new JLabel("Launching...", SwingConstants.CENTER);
progressBar = new JProgressBar(0, 100);
progressBar.setIndeterminate(true);
panel.add(label, BorderLayout.CENTER);
panel.add(progressBar, BorderLayout.PAGE_END);
initUI(panel);
worker = new LauncherWorker(this);
worker.addPropertyChangeListener((PropertyChangeListener)this);
}
private void initUI(final Component panel) {
if (!SwingUtilities.isEventDispatchThread()) {
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
DirectaChatLauncher.this.initUI(panel);
} //run()
});
return;
}
Container contentPane = frame.getContentPane();
contentPane.setLayout(new BorderLayout());
contentPane.add(panel, BorderLayout.PAGE_END);
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
#Override
public void propertyChange(PropertyChangeEvent evt) {
if ("progress".equals(evt.getPropertyName())) {
int progress = (Integer) evt.getNewValue();
progressBar.setValue(progress);
}
}
private void setProgression(final String msg) {
label.setText(msg);
}
class LauncherWorker extends SwingWorker<Boolean, String> {
private final Launcher LAUNCHER;
public LauncherWorker(Launcher launcher) {
super();
LAUNCHER = launcher;
}
#Override
protected Boolean doInBackground() throws Exception {
setProgress(0);
publish("Started");
...
setProgress(100);
publish("Launched");
Thread.sleep(1000);
return Boolean.TRUE;
}
#Override
protected void process(List<String> chunks) {
LAUNCHER.setProgression(chunks.get(0));
}
#Override
public void done() {
LAUNCHER.done();
}
}
}
is it fine since the elements weren't displayed yet? or should I move all into initUI()?
In the Swing separable model architecture, a view component listens to its model. Because a view may respond arbitrarily to events generated by model updates, the corresponding model must also be updated on the EDT. You can mitigate latency via one of two basic approaches:
Use EventQueue.invokeLater() from a separate thread, as shown here.
Use SwingWorker to obtain the additional benefits enumerated here.
Swing Threading Policy states:
In general Swing is not thread safe. All Swing components and related classes, unless otherwise documented, must be accessed on the event dispatching thread.
Typical Swing applications do processing in response to an event generated from a user gesture. For example, clicking on a JButton notifies all ActionListeners added to the JButton. As all events generated from a user gesture are dispatched on the event dispatching thread, most developers are not impacted by the restriction.
Where the impact lies, however, is in constructing and showing a Swing application. Calls to an application's main method, or methods in Applet, are not invoked on the event dispatching thread. As such, care must be taken to transfer control to the event dispatching thread when constructing and showing an application or applet. The preferred way to transfer control and begin working with Swing is to use invokeLater. The invokeLater method schedules a Runnable to be processed on the event dispatching thread.
Related
When I try to use any kind of delay on my code the program gets delayed but the JLabel that was put before the delay gets updated after the program ends.
I want the program to:
update the JLabel on the GUI
wait for 5 seconds
update the JLabel again with diferent text
wait another 5 seconds
I have tried with timers, invokelater, invokeandwait, thread.sleep and others.
The problems is that the GUI does get delayed at the right spot but the GUI does not update the JLabel ath place where the code is located. The JLabel gets updated after the program ends.
I want the user to be able to read the text for 5 seconds then read another text for another 5 seconds in order. I do not want the program to run the gui pause at a cetain spot then at end just update the JLabel. I want the gui to get updated before the delay. I do not want the same thing that when I used a timer to happen where I type in a setText for the JLabel before the Timer is typed and then when I run the program the timer works but the JLabel gets updated after the delay(It is not what I want).
The way to achieve that is either using a Swing Worker, either a a Swing Timer. A Swing worker runs a task in background and at the same time it is capable of publishing GUI changes in the Event dispatch thread (the thread where the GUI runs). A SwingTimer can be considered as a simplified version of a Swing Worker, that only runs a task after some time in the Event Dispatch Thread. (Consider a worker that sleeps the thread in background, and after the sleep, it runs the task in the Gui thread).
There are a lot of examples online, like this one and this one.
If you do not want to do something in background, a Timer solution sounds "simpler". Take a look at How can I pause/sleep/wait in a java swing app?
An example where it is closer to what you need (with a worker):
public class WorkerExample extends JFrame {
private static final long serialVersionUID = 6230291564719983347L;
private JLabel label;
public WorkerExample() {
super("");
setDefaultCloseOperation(EXIT_ON_CLOSE);
setLayout(new FlowLayout());
SwingWorker<Void, String> worker = new SwingWorker<Void, String>() {
#Override
protected Void doInBackground() throws Exception {
publish("Started....");
Thread.sleep(1500);
for (int i = 0; i < 5; i++) {
publish("Number of iterations: " + i);
//Do something
Thread.sleep(3500);
}
return null;
}
#Override
protected void process(List<String> chunks) {
String chunk = chunks.get(0);
label.setText(chunk);
}
#Override
protected void done() {
label.setText("Done.");
}
};
JButton button = new JButton("Start");
button.addActionListener(e -> worker.execute());
add(button);
label = new JLabel("Nothing yet.");
add(label);
setSize(400, 400);
setLocationByPlatform(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(() -> {
new WorkerExample().setVisible(true);
});
}
}
You can experiment with these in order to understand how a SwingWorker works, but I strongly recommend you to read concurrency in Swing before doing that.
I have 2 icons, and I want them to change every second. I also want it to always run and not stop. I am doing it with this code but I am not successful.
public static void main(String[] args) {
Timer timer = new Timer();
JFrameLeds jframeLeds = new JFrameLeds();
jframeLeds.setVisible(true);
TimerTask timerTask = new TimerTask() {
#Override
public void run() {
Icon icono;
icono = new ImageIcon(getClass().getResource("camera.png"));
jframeLeds.jLabel1.setIcon(icono);
icono = new ImageIcon(getClass().getResource("target.png"));
jframeLeds.jLabel1.setIcon(icono);
}
};
timer.schedule(timerTask, 0, 1000);
}
Using Thread class, or TimerTask is not recommended in a Swing environment. You should be using Swing Timers or Swing Workers since component updates should only take place to the Event Dispatch Thread. Take a look at this example.
However, in your case a flag boolean might be required in order to achieve what you want. An example that changes icons to a label:
public class ChangeIconsTest extends JFrame {
private boolean icon1IsActive;
public ChangeIconsTest(Icon icon1, Icon icon2) {
super("test");
setDefaultCloseOperation(EXIT_ON_CLOSE);
setLayout(new BorderLayout());
JLabel label = new JLabel(icon1);
icon1IsActive = true;
Timer swingTimer = new Timer(1000, e -> {
label.setIcon(icon1IsActive ? icon2 : icon1);
icon1IsActive = !icon1IsActive;
});
swingTimer.start();
add(label);
pack();
}
public static void main(String[] args) {
SwingUtilities.invokeLater(() -> {
try {
ImageIcon icon1 = new ImageIcon(
new URL("https://4.img-dpreview.com/files/p/E~TS590x0~articles/3925134721/0266554465.jpeg"));
Icon icon2 = new ImageIcon(new URL("https://www.sample-videos.com/img/Sample-png-image-500kb.png"));
ChangeIconsTest test = new ChangeIconsTest(icon1, icon2);
test.setVisible(true);
} catch (MalformedURLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
});
}
}
As many people here reminded, using TimerTask class from java.util is highly NOT recommended while working in Swing or JavaFX environment.
The Swing components aren't thread-safe, changing the state or repainting the components in different thread than the one used by Swing components may lead to unexpected behaviour and strange bugs.
The Swing and AWT components are using Event Dispach Thread as main background thread to process the events. Events are fired inside every component method that might cause the change of interface. The setIcon() and even setText() methods of JLabel are also firing an event to the EDT.
To avoid future bugs every component state change should be done undnder EDT. The EDT can be called through EventQueue.invokeLater(Runnable), but since you are using Swing, you can call the SwingUtilities.invokeLater(Runnable) which calls the EventQueue inside.
The invokeLater method schedules the task and returns, there's also a invokeAndWait which schedules the task and waits until it's finished before returning.
For the sample below I borrowed the icon urls from the George Z. answer.
Sample code for covering the timed icon change:
public class TimedIconChange {
static String ICON_1_URL = "https://4.img-dpreview.com/files/p/E~TS590x0~articles/3925134721/0266554465.jpeg";
static String ICON_2_URL = "https://www.sample-videos.com/img/Sample-png-image-500kb.png";
static String ICON_3_URL = "http://www.frankieballard.com/sites/g/files/g2000005856/f/Sample-image10-highres.jpg";
public static void main(String[] args) throws MalformedURLException {
Icon icon1 = new ImageIcon(new URL(ICON_1_URL));
Icon icon2 = new ImageIcon(new URL(ICON_2_URL));
Icon icon3 = new ImageIcon(new URL(ICON_3_URL));
List<Icon> circularIcons = new ArrayList<>() {
int i = 0;
#Override
public Icon get(int index) {
return get();
}
private Icon get() {
if (i == size()) {
i = 0;
}
return super.get(i++);
}
};
circularIcons.add(icon3);
circularIcons.add(icon2);
circularIcons.add(icon1);
SwingUtilities.invokeLater(() -> {
JFrame frame = new JFrame();
JLabel label = new JLabel();
label.setIcon(icon1);
frame.setLayout(new BorderLayout());
frame.add(label);
frame.pack();
frame.setVisible(true);
new Timer(1000, e -> label.setIcon(circularIcons.get(0))).start();
});
}
}
The sample contains a little implementation of circular list for circularIcons variable, to reduce the need of using boolean flag.
Additionaly, for longer tasks which are supposed to be working in the background using the SwingWorker class is recommended.
References and further reading on EDT:
https://en.wikipedia.org/wiki/Event_dispatching_thread
Why should I use a separate thread to show a GUI in JAVA
Why does my boilerplate Java desktop app JFrame use EventQueue.invokeLater in the main method?
https://docs.oracle.com/javase/tutorial/uiswing/concurrency/index.html
What is the best practice way to start a java swing application? Maybe there is another way to do it.
I want to know if i have to use the SwingUtilities class to start the application (secound possibility) or not (first possibility).
public class MyFrame extends JFrame {
public void createAndShowGUI() {
this.setSize(300, 300);
this.setDefaultCloseOperation(EXIT_ON_CLOSE);
// add components and stuff
this.setVisible(true);
}
public static void main(String[] args) {
// First possibility
MyFrame mf = new MyFrame();
mf.createAndShowGUI();
// Secound possibility
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
MyFrame mf = new MyFrame();
mf.createAndShowGUI();
}
});
}
}
Only the second way is correct. Swing components must be created and accessed only in the event dispatch thread. See concurrency in swing. The relevant quote:
Why does not the initial thread simply create the GUI itself? Because almost all code that creates or interacts with Swing components must run on the event dispatch thread. This restriction is discussed further in the next section.
So yes, you need to use invokeLater().
When a user clicks a button, a long task of approximately 10 seconds will run. During this time I want to show a progress bar to the user. But the main thread has to wait for the worker thread to finish because the worker thread will set a variable that the main thread will use. If I don't wait the worker thread I will get a NullPointerException when using the variable. So after the worker thread finishes, I will also close the progress bar dialog.
When I wait for the worker thread using join() the progress bar dialog shows (interestingly without the progress bar though) and hangs there.
Thread runnable = new Thread() {
public void run() {
try {
System.out.println("thread basladi");
threadAddSlaveReturnMessage = request.addSlave(
ipField.getText(), passField.getText(),
nicknameField.getText());
System.out.println("thread bitti");
} catch (LMCTagNotFoundException e) {
e.printStackTrace();
}
}
};
Thread runnable_progress = new Thread() {
public void run() {
JTextArea msgLabel;
JDialog dialog;
JProgressBar progressBar;
final int MAXIMUM = 100;
JPanel panel;
progressBar = new JProgressBar(0, MAXIMUM);
progressBar.setIndeterminate(true);
msgLabel = new JTextArea("deneme");
msgLabel.setEditable(false);
panel = new JPanel(new BorderLayout(5, 5));
panel.add(msgLabel, BorderLayout.PAGE_START);
panel.add(progressBar, BorderLayout.CENTER);
panel.setBorder(BorderFactory.createEmptyBorder(11, 11, 11, 11));
dialog = new JDialog(Frame.getFrames()[0], "baslik", true);
dialog.getContentPane().add(panel);
dialog.setResizable(false);
dialog.pack();
dialog.setSize(500, dialog.getHeight());
dialog.setLocationRelativeTo(null);
dialog.setDefaultCloseOperation(JDialog.DO_NOTHING_ON_CLOSE);
dialog.setAlwaysOnTop(false);
dialog.setVisible(true);
msgLabel.setBackground(panel.getBackground());
}
};
runnable.start();
System.out.println("runnable start");
runnable_progress.start();
System.out.println("progress start");
runnable.join();
System.out.println("runnable join");
runnable_progress.join();
System.out.println("progress join");
if (threadAddSlaveReturnMessage.equalsIgnoreCase("OK")) {
fillInventoryTable(inventoryTable);
JOptionPane.showMessageDialog(this, messages.getString("centrum.addslavepanel.SUCCESS"), null, JOptionPane.INFORMATION_MESSAGE);
}
"progress join"
doesn't get printed.
You can use a SwingWorker here. A short example :
/*
* To change this template, choose Tools | Templates
* and open the template in the editor.
*/
package org.godel.nio;
import java.awt.BorderLayout;
import java.util.List;
import javax.swing.*;
/**
*
* #author internet_2
*/
public class Test {
public static void main(String[] args) {
new Test().doJob();
}
public void doJob() {
JTextArea msgLabel;
JProgressBar progressBar;
final int MAXIMUM = 100;
JPanel panel;
progressBar = new JProgressBar(0, MAXIMUM);
progressBar.setIndeterminate(true);
msgLabel = new JTextArea("deneme");
msgLabel.setEditable(false);
panel = new JPanel(new BorderLayout(5, 5));
panel.add(msgLabel, BorderLayout.PAGE_START);
panel.add(progressBar, BorderLayout.CENTER);
panel.setBorder(BorderFactory.createEmptyBorder(11, 11, 11, 11));
final JDialog dialog = new JDialog();
dialog.getContentPane().add(panel);
dialog.setResizable(false);
dialog.pack();
dialog.setSize(500, dialog.getHeight());
dialog.setLocationRelativeTo(null);
dialog.setDefaultCloseOperation(JDialog.DO_NOTHING_ON_CLOSE);
dialog.setAlwaysOnTop(false);
dialog.setVisible(true);
msgLabel.setBackground(panel.getBackground());
SwingWorker worker = new SwingWorker() {
#Override
protected void done() {
// Close the dialog
dialog.dispose();
}
#Override
protected void process(List chunks) {
// Here you can process the result of "doInBackGround()"
// Set a variable in the dialog or etc.
}
#Override
protected Object doInBackground() throws Exception {
// Do the long running task here
// Call "publish()" to pass the data to "process()"
// return something meaningful
return null;
}
};
worker.execute();
}
}
Edit : "publish()" should be called in "doInBackground()" to pass the data to "process()".
you have the issue with Concurency is Swing, your GUI is visible after all thread are done
is possible to moving with JProgressBar (I'm talking about you code) but you have to
create and show JDialog, create once time and reuse this container
then to start Thread,
better could be from Runnable#Thread
output to the Swing GUI must be wrapped into invokeLater()
this is exactly job for using SwingWorker and with PropertyChangeListener
As the previous answers already mentioned, SwingWorker is the way to go, if use want to use concurrency with Swing.I found this SwingWorker and ProgressBar tutorial quite useful in understanding how it all works together.
Coming back to your actual problem: I assume you use a GUI, because you stated the user has to click a button. The question is, what is your "main thread" doing? Does it really have to run all the time? Doesn't look like it. Because you said the thread needs a variable which is set by another thread, which is a result of a user interaction. In short: Why does it need to run if it's dependent on a user interaction anyway? The usual way would be to first get all the data you need and then run the calculations or whatever. In your case, either run everything in a single background thread(set the variable first then do the rest), started by the ActionListener of your button or run the other thread after the thread where you set the variable has completed.You could for example use the method done(), provided by SwingWorker, to launch the next task. Or if you really have to, you could wait in a loop for task.isDone()to return true. But don't forget to check for isCancelled() too.Anyway, I think you should rethink your design. Because what I can see from the limited information provided looks overly complicated to me.
First of all: I know this question seems to have been asked a few million times, but none of the answers given to other questions seem to work with me.
Sometimes, when I run Message.popup(String, int) in the code below, the text displays correctly, but sometimes the JDialog is empty, like if the component wasn't added at all.
public class Message extends JDialog {
private int width;
private int height;
private JLabel content;
public Message(String _content, int _margin) {
super();
this.content = new JLabel(_content);
content.setFont(new Font("Monospaced", Font.BOLD, 20));
this.margin = _margin;
this.width = content.getPreferredSize().width + _margin;
this.height = content.getPreferredSize().height + _margin;
createComponents();
setProperties();
}
public static void popup(String _content, int _time) {
if (SwingUtilities.isEventDispatchThread()) {
runPopup(_content, _time);
}
else {
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
runPopup(_content, _time);
}
});
}
}
private static void runPopup(String _content, int _time) {
final Message message = new Message(_content);
new Timer(_time, new ActionListener() {
#Override
public void actionPerformed(ActionEvent arg0) {
message.dispose();
}
}).start();
}
private void createComponents() {
setLayout(new BorderLayout());
Box box = Box.createHorizontalBox();
box.add(Box.createHorizontalGlue());
box.add(content, BorderLayout.CENTER);
box.add(Box.createHorizontalGlue());
add(box);
}
private void setProperties() {
setSize(width, height);
setLocation(Coordinator.calculateCenteredWindowLocation(width, height));
setUndecorated(true);
setResizable(false);
setTitle(content.getText());
setVisible(true);
update(getGraphics());
}
}
Without the update(getGraphics());, the frame is always empty, but with it, it depends of what direction the wind is blowing... (go figure!)
As mentioned by #Riduidel, it is important that anything Swing-related occur on the Event Dispatch Thread, or EDT. This is because Swing is not thread-safe. When invoking popup(), you ought to do the following
if(SwingUtilities.isEventDispatchThread()){
Message.popup(...);
}
else{
SwingUtilities.invokeLater(new Runnable(){
#Override
public void run(){
Message.popup(...);
}
});
}
This will ensure that the JFrame is created on the EDT. Also, from the code snippet you've posted, it would seem likely that Message should have a private constructor. In addition, since you're not doing any custom rendering, why not just make a JFrame member variable instead of extending the class? -- seems a bit superfluous to me.
Regardless, you should also never sleep in the EDT either, since this will make the GUI appear to "freeze" and blocks execution of other queued events. When performing long-running tasks, use either SwingWorker, or as #Riduidel mentioned, javax.swing.Timer. But if you prefer to use the java.util.Timer, use the SwingUtilities utility class as shown above to post the Runnable task on the EventQueue to be executed in the EDT.
EDIT
Here is what I'd do (and yes, it works)
public class Message {
// Private constructor to prevent external instantiation
private Message(){
}
public static void createAndShowDialog(final String content, final int time){
final JDialog dialog = new JDialog();
dialog.setLayout(new BorderLayout());
dialog.setUndecorated(true);
JLabel label = new JLabel(content);
label.setFont(new Font("Monospaced", Font.BOLD, 20));
Box b = Box.createHorizontalBox();
b.add(Box.createHorizontalGlue());
b.add(label, BorderLayout.CENTER);
b.add(Box.createHorizontalGlue());
dialog.add(b);
dialog.pack();
dialog.setLocationRelativeTo(null);
dialog.setVisible(true);
// kick-off timer
Timer t = new Timer(time, new ActionListener() {
#Override
public void actionPerformed(ActionEvent arg0) {
dialog.dispose();
}
});
t.setRepeats(false);
t.start();
}
}
And wherever you invoke createAndShowDialog(...), do the following
SwingUtilities.invokeLater(new Runnable(){
#Override
public void run(){
Message.createAndShowDialog("Content", 5000); // wait 5 seconds before disposing dialog
}
});
Are you sure your code is executing in the EDT ? indeed, if not (which is what I expect to be, since you sleep the current thread, what Swing would typically don't like), your frame will have trouble rendering.
To avoid those typical Swing threading issues, please take a look at the SwingUtilities class, which provide you methods to ensure you're running in EDT. Additionnaly, instead of directly sleeping your thread, you could repalce it with a Swing javax.swing.Timer (beware not to confuse it with the java.util.Timer).
update(getGraphics());
Never use the update() method or the getGraphics() method.
Invoking update() is used for AWT NOT Swing.
If you need to do custom painting then you override the paintComponent() method of your component which already has access to the graphics object.