Develop Reference

JavaFX - How to use an executor to run tasks one at a time?

I'm trying to create a Javafx application that takes screenshots from a URL. Where I'm running into issues is with threading. In my main method, I'm trying to run the two screenshots but it's getting stuck after loading the first page. I've tried to wrap the monitorPageStatus() (since it calls the actual saveToPng() function) method in a task that is submitted to the executor (code below). How can I properly submit the task to the executor so both screenshots are taken?
public class InsightScreenshot {
{
// Clever way to init JavaFX once
JFXPanel fxPanel = new JFXPanel();
}
private Browser browser;
public Stage stage;
private Timer timer = new java.util.Timer();
private ExecutorService exec = Executors.newSingleThreadExecutor(r -> {
Thread t = new Thread(r);
t.setDaemon(true); // allows app to exit if tasks are running
return t ;
});
#SuppressWarnings("restriction")
/**
*
* #param url
* #param imageName add png extension
*/
public void showWindow(String url, String imagePath) {
// JavaFX stuff needs to be done on JavaFX thread
Platform.runLater(new Runnable() {
private Stage window;
#SuppressWarnings("restriction")
#Override
public void run() {
Stage window = new Stage();
window.setTitle(url);
browser = new Browser(url);
monitorPageStatus(imagePath, window);
VBox layout = new VBox();
layout.getChildren().addAll(browser);
Scene scene = new Scene(layout);
window.setScene(scene);
//window.setOnCloseRequest(we -> System.exit(0));
window.show();
}
});
}
private void monitorPageStatus(String imageName, Stage window) {
timer.schedule(new TimerTask() {
#SuppressWarnings("restriction")
public void run() {
Platform.runLater(() -> {
if (browser.isPageLoaded()) {
System.out.println("Page now loaded, taking screenshot...");
saveAsPng(imageName);
window.close();
cancel();
} else
System.out.println("Loading page...");
});
}
}, 1000, 1000);
}
private void saveAsPng(String imageName) {
WritableImage image = browser.snapshot(new SnapshotParameters(), null);
//TODO change file path?
File file = new File(imageName);
try {
ImageIO.write(SwingFXUtils.fromFXImage(image, null), "png", file);
System.out.println("Screenshot saved as " + imageName);
} catch (IOException e) {
e.printStackTrace();
}
}
public static void main(String[] args) {
InsightScreenshot pic = new InsightScreenshot();
pic.showWindow("ttps://www.google.com", "/images/google.png");
InsightScreenshot pic2 = new InsightScreenshot();
pic2.showWindow("https://www.facebook.com", "/images/fb.png");
}
}

JLayer Player overwrites refesh of SWT widgets when placed in a loop

I am attempting to make an application that retrieves images and .mp3 files and transitions from one image to the next once the audio has finished. The underlying framework of how I transition between these images is a little convoluted, but I have managed to get an action in SWT that successfully enables me to manually transition from one to the next. However, a problem has arisen when I've tried to automate it; when placed into a loop, my playAudio() method begins before all of the calls I make in my displayShow() method have resolved, which results in a blank window, despite the audio still playing.
Here is the run method for the action that I want to start the show:
Action startAction = new Action("Start") {
public void run() {
//do {
displayShow();
playAudio();
//} while(true);
}
};
Here is playAudio(). I am able to PLAY the audio without incident:
public void playAudio() {
final String audio = "Happy_Birthday.mp3";
audioLatch = new CountDownLatch(1);
audioThread = new Thread() {
public void run() {
try {
Player player = new Player
(new BufferedInputStream
(new FileInputStream(audio)));
player.play();
audioLatch.countDown();
} catch (JavaLayerException e) {
} catch (FileNotFoundException e) {
} catch (Exception e) {
}
}
};
audioThread.start();
try {
audioLatch.await();
} catch (InterruptedException e) {
}
}
And here is displayShow():
private void displayShow() {
new Thread() {
public void run() {
Display.getDefault().asyncExec(new Runnable() {
public void run() {
Control[] children = container.getChildren();
for (int i = 0; i < children.length; i++) {
children[i].dispose();
}
show.showSlide(container);
container.layout();
}
});
}
}.start();
}
show.showSlide returns a composite whose parent is container, which is the immediate child of the highest parent composite. Within the newly created composite, an image is added to a label and the label's parent is assigned to composite. I realize whether displayShow() is in a separate thread or not seems to be immaterial; this was just the last thing I tried.
It is not solely the addition of the loop that causes the refresh to not execute. The only way I can get the manual transition to work is if I remove the CountDownLatch from the playAudio() method. Were I to remove this latch, the only way to encase these two methods in a loop would be embedded while loops, which seem to hog a fair amount of the CPU and still does not solve my problem. Am I missing anything?

The audioLatch.await() is blocking the main program thread, this is the thread that all SWT operations run on so the Display.asyncExec runnables are just being queued until the thread is available.
If you really must wait in the playAudio method you could run the display event loop there until the background thread is finished:
while (! background thread finished)
{
if (!display.readAndDispatch())
display.sleep();
}

Display message during loading

I have a JavaFX with TabPane which holds Java Objects with data into different tabs. I found that when the content of the tab takes time to load because there are SQL queries for execution the application just hangs. Is there any way to display some "Loading" message during the content utilization? for example:
Tab.setContent(<some_heavy_Java_Object>);
Is there any workaround to solve this in JavaFX or Java?
P.S I tested this code sample but I get error when I try to run the code:
TabContentInfrastructure content;
class GetDailySalesService extends Service<ObservableList<Object>>
{
#Override
protected Task createTask()
{
return new GetDailySalesTask();
}
}
class GetDailySalesTask extends Task<ObservableList<Object>>
{
#Override
protected ObservableList<Object> call() throws Exception
{
content = new TabContentInfrastructure();
return (ObservableList<Object>) content.initTestTabContentData();
}
}
..........
VBox vbox = new VBox();
content = new TabContentInfrastructure();
vbox.getChildren().add(content.initTestTabContentData());
GetDailySalesService service = new GetDailySalesService();
Region veil = new Region();
veil.setStyle("-fx-background-color: rgba(0, 0, 0, 0.4)");
veil.setPrefSize(240, 160);
ProgressIndicator p = new ProgressIndicator();
p.setMaxSize(140, 140);
p.progressProperty().bind(service.progressProperty());
veil.visibleProperty().bind(service.runningProperty());
p.visibleProperty().bind(service.runningProperty());
//tableView.itemsProperty().bind(service.valueProperty());
StackPane stack = new StackPane();
stack.getChildren().addAll(vbox, veil, p);
service.start();
tabdata.setContent(stack);
Can you help me to solve this issue.
Another attempt to solve the issue:
Task<VBox> task = new Task<VBox>()
{
#Override
protected VBox call() throws Exception
{
TabContentInfrastructure content = new TabContentInfrastructure();
return content.initTestTabContentData();
}
};
Thread th = new Thread(task);
th.setDaemon(true);
th.start();
Region veil = new Region();
veil.setStyle("-fx-background-color: rgba(0, 0, 0, 0.4)");
veil.setPrefSize(240, 160);
ProgressIndicator p = new ProgressIndicator();
p.setMaxSize(140, 140);
//p.progressProperty().bind(service.progressProperty());
veil.visibleProperty().bind(task.runningProperty());
p.visibleProperty().bind(task.runningProperty());
//vb.visibleProperty().bind(service.runningProperty().not());
//tableView.itemsProperty().bind(service.valueProperty());
StackPane stack = new StackPane();
task.setOnSucceeded(new EventHandler<WorkerStateEvent>()
{
#Override
public void handle(WorkerStateEvent t){
System.out.print("Entered setOnSucceeded**********" + t.getSource().getValue());
stack.getChildren().clear();
stack.getChildren().addAll(task.getValue());
}
});
stack.getChildren().addAll(veil, p);
tabdata.setContent(stack);
This time the result is null.
And another unsuccessful attempt.
StackPane stack = new StackPane();
Region veil = new Region();
ProgressIndicator p = new ProgressIndicator();
Task<VBox> task = new Task<VBox>()
{ // create new task
#Override
public VBox call() throws InterruptedException
{
Platform.runLater(new Runnable()
{ // USE THIS INSTEAD
#Override
public void run()
{
try
{
// ui updates here(inside application thread)
// this is needed if you want to update your ui
// you cannot update any ui from outside the application thread
TabContentInfrastructure content = new TabContentInfrastructure();
//stack.getChildren().clear();
stack.getChildren().addAll(content.initTestTabContentData());
}
catch (InterruptedException ex)
{
//Logger.getLogger(InfrastructureDataTabs.class.getName()).log(Level.SEVERE, null, ex);
}
}
});
return null;
}
};
new Thread(task).start();
veil.setStyle("-fx-background-color: rgba(0, 0, 0, 0.4)");
veil.setPrefSize(240, 160);
p.setMaxSize(140, 140);
p.progressProperty().bind(task.progressProperty());
veil.visibleProperty().bind(task.runningProperty());
p.visibleProperty().bind(task.runningProperty());
//vb.visibleProperty().bind(service.runningProperty().not());
//tableView.itemsProperty().bind(service.valueProperty());
stack.getChildren().addAll(veil, p);
tabdata.setContent(stack);

you must load the data in a different Task Thread, I see that you are trying to do the same. The problem with your code is that you are not updating your progress bar. You must use updateProgress as shown here
http://docs.oracle.com/javafx/2/threads/jfxpub-threads.htm#BABGJIDB
Here is a very nice example from Jewelsea where he has very nicely displayed the use of Task and how to use it to update the progress on the UI
Update progress bar and multiple labels from thread
Here you can find out how to use the Task as well as update the UI from the task
Some more Nice examples are
https://community.oracle.com/message/9927179#9927179
https://community.oracle.com/message/10631701#10631701

You should just execute the expensive computations in another thread and then update e.g. a progresss bar in the javafx application thread.
Also your application wont hang during the process anymore.
Like this:
Task task = new Task<Void>() { // create new task
#Override
public Void call() {
// do expensive computations here
Platform.runLater(new Runnable() { // return to application thread
#Override
public void run() {
// ui updates here(inside application thread)
}
});
return null;
}
};
new Thread(task).start(); // execute task in new thread
Hope it helps, Laurenz.
EDIT -------------
Task<Void> task = new Task<Void>() { // create new task
#Override
public Void call() {
try {
Thread.sleep(50); // this simulates expensive computations(in your case loading) - your app would hang for this duration
} catch (InterruptedException e) {
e.printStackTrace();
}
// REMOVE THE SLEEP AND PUT YOUR TASK HERE
// Main.this.root.setPrefHeight(50); // would NOT work(because outside application thread)
Platform.runLater(new Runnable() { // USE THIS INSTEAD
#Override
public void run() {
// ui updates here(inside application thread)
// this is needed if you want to update your ui
// you cannot update any ui from outside the application thread
}
});
return null;
}
};
new Thread(task).start(); // execute task in new thread

Indeterminate Progress bar wont show

I have an application that copies files (via ADB) to an android tablet. It takes some time so I want to display a popup with an indeterminate progress bar on it. When the copy task is complete then I want to be able to stop the progress bar and let the user close the dialog.
At the moment I have not added the extra dialog box and am just trying to get the progress bar working. The problem I have is that the progress bar is not showing at the start of the task, but I dont know why. The progressbar shows when the dialog box saying sync complete appears. The code is:
progress = new JProgressBar(0, 100);
progress.setForeground(new Color(255, 99, 71));
progress.setIndeterminate(true);
progress.setValue(0);
progress.setPreferredSize( new Dimension( 300, 20 ) );
progress.setBounds( 278, 12, 260, 20 );
progress.setVisible(false);
progress.setString("Sync in progress");
progress.setStringPainted(true);
contentPane.add(progress);
pushtotab = new JButton("");
pushtotab.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent arg0) {
if (buildpathset==1){
try{
setCursor(Cursor.getPredefinedCursor(Cursor.WAIT_CURSOR));
progress.setVisible(true);
wiredsync();
}finally{
JOptionPane.showMessageDialog(null, "sync complete. ",null, buildpathset);
setCursor(Cursor.getDefaultCursor());
progress.setVisible(false);
}}else{
//warning in here later - TO Do
}
}
});
public void wiredsync(){
try {
Process process = Runtime.getRuntime().exec("adb" + " push "+ buildpath + " " + adbtabletsync);
InputStreamReader reader = new InputStreamReader(process.getInputStream());
Scanner scanner = new Scanner(reader);
scanner.close();
int exitCode = process.waitFor();
System.out.println("Process returned: " + exitCode);
} catch(IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}//end
Thanks for the help,
Andy

pooyan has the right idea -- do the long running process in a background thread -- but gives the wrong library example, since your program is a Swing program and not an Android program. The canonical answer to this for Swing is to do your long-running task in the doInBackground() method of a SwingWorker.
Please hold while I find a better example...
Something like so:
if (buildpathset == 1) {
setCursor(Cursor.getPredefinedCursor(Cursor.WAIT_CURSOR));
progress.setVisible(true);
// create my SwingWorker object
final SwingWorker<Void, Void> myWorker = new SwingWorker<Void, Void>() {
protected Void doInBackground() throws Exception {
// here is my long running task, calling in background
// thread
wiredsync();
return null;
};
};
// this allows me to be notified when the SwingWorker has
// finished
myWorker.addPropertyChangeListener(new PropertyChangeListener() {
#Override
public void propertyChange(PropertyChangeEvent pcEvt) {
// if the SwingWorker is done
if (pcEvt.getNewValue() == SwingWorker.StateValue.DONE) {
// notify the user
JOptionPane.showMessageDialog(null, "sync complete. ",
null, buildpathset);
setCursor(Cursor.getDefaultCursor());
progress.setVisible(false);
try {
// one way to catch any errors that occur in
// SwingWorker
myWorker.get();
} catch (InterruptedException | ExecutionException e) {
e.printStackTrace();
}
}
}
});
// run my SwingWorker
myWorker.execute();
} else {
// warning in here later - TO Do
}
For more on this, please check out: Lesson: Concurrency in Swing

i think your problem is that you don't use thread . I mean after you turn visibility of your progress bar to true , you should define your long task in a thread. I'm Not familiar with Swing But
take Look there for Swing (sorry if it's no use full):
http://www.java-tips.org/java-se-tips/javax.swing/how-to-handle-long-running-tasks-in-a-swing-applic.html
and there for android :http://www.mkyong.com/android/android-progress-bar-example/

JPanel doesn't load in JFrame

I have a problem showing my progress bar when reading a file in Java.
All works as intended, user choose a file, the program must show the progress bar (but it loads an empty blank frame), process the file and then load the results on another window.
I can't get the program to show the content of the progress bar dialog.
A little help here would be really appreciated.
Here is the code of the 3 methods involved.
//this method reads the file
public void processFile(File arch) {
aFile = arch;
Thread threadForSearch = new Thread() {
#Override
public void run() {
try{
listaProveedoresTango = controladoraConsultas.traerProveedores();
listaProveedoresAFIP = new LinkedList();
BufferedReader data = new BufferedReader(new FileReader(aFile));
String s;
while ((s = data.readLine()) != null) {
//long task
}
data.close();
}catch (Exception e){
System.err.println("Error: " + e.getMessage());
}
}
};
interfacesController.loadProgressBar();
threadForSearch.start();
try {
threadForSearch.join();
} catch (InterruptedException ex) {
Logger.getLogger(Controladora.class.getName()).log(Level.SEVERE, null, ex);
}
this.interfacesController.closeProgressBar();
this.interfacesController.loadResults(someStuff);
}
//load a progress bar
public void loadProgressBar(){
JProgressBar pb = new JProgressBar(0,100);
pb.setPreferredSize(new Dimension(175,20));
pb.setString("Processing Data");
pb.setStringPainted(true);
pb.setIndeterminate(true);
JLabel infoLabel = new JLabel("Reading File: ");
JButton cancelButton = new JButton("Cancel");
cancelButton.addActionListener(new AbstractAction() {
#Override
public void actionPerformed(ActionEvent evt) {
exitSystem();
}
});
cancelButton.setVerticalAlignment(SwingConstants.CENTER);
JPanel center_panel = new JPanel();
center_panel.add(infoLabel);
center_panel.add(pb);
center_panel.add(cancelButton);
center_panel.setLayout(new BoxLayout(center_panel,BoxLayout.Y_AXIS));
dialog = new JDialog((JFrame)null, "Processing ...");
dialog.getContentPane().add(center_panel, BorderLayout.CENTER);
dialog.setSize(100, 100);
dialog.setLocationRelativeTo(null);
dialog.pack();
dialog.setVisible(true);
}
//close the open progress bar
public void closeProgressBar(){
this.dialog.dispose();
}
Solved with SwingWorker, i post a summarized code:
public void processFile(File arch) {
aFile = arch;
final SwingWorker searchOnFile = new SwingWorker(){
#Override
protected Object doInBackground() throws Exception {
try{
BufferedReader data = new BufferedReader(new FileReader(aFile));
String s;
while ((s = data.readLine()) != null) {
//long task
}
data.close();
}catch (Exception e){ //Catch exception if any
System.err.println("Error: " + e.getMessage());
}
interfacesController.closeProgressBar();
interfacesController.loadResults(someStuff);
return null;
}
};
interfacesController.showProgressBar();
searchOnFile.execute();
}
interfacesController contains all the methods to work with GUIs, showProgressBar() is used to show the bar and closeProgressBar() do the opposite. Thank you guys!

Short of more useful code, I suggest using a SwingWorker.
An abstract class to perform lengthy GUI-interaction tasks in a background thread. Several background threads can be used to execute such tasks. ..
Given the nature of the task, you might also look at ProgressMonitorInputStream.
..creates a progress monitor to monitor the progress of reading the input stream. If it's taking a while, a ProgressDialog will be popped up to inform the user. If the user hits the Cancel button an InterruptedIOException will be thrown on the next read. All the right cleanup is done when the stream is closed.