Develop Reference

How to make a method call wait for an animation to finish

I want to make a notification window with animated text. A notification would be sent by a button click and the animation would start playing. My problem is that when I click the button again before the previous animation is done, two animations get executed at once. How do I make each method call of "sendMessage()" wait for the other to finish? If it has any significance there are multiple nodes that call the sendMessage() method in my program unlike in my MRE, so I want some kind of Queue with messages. Here is my MRE:
public class AnimationTest extends Application {
private final Label messageLabel = new Label();
#Override
public void start(Stage stage) throws IOException {
VBox vBox = new VBox();
vBox.setAlignment(Pos.CENTER);
Scene scene = new Scene(vBox, 320, 240);
vBox.getChildren().add(messageLabel);
Button button = new Button();
button.setOnAction(event -> sendMessage("Some animated text."));
vBox.getChildren().add(button);
stage.setScene(scene);
stage.show();
}
private void sendMessage(String message) {
final IntegerProperty i = new SimpleIntegerProperty(0);
Timeline timeline = new Timeline();
KeyFrame keyFrame = new KeyFrame(
Duration.millis(40),
event -> {
if (i.get() > message.length()) {
timeline.stop();
} else {
messageLabel.setText(message.substring(0, i.get()));
i.set(i.get() + 1);
}
});
timeline.getKeyFrames().add(keyFrame);
timeline.setCycleCount(Animation.INDEFINITE);
timeline.play();
}
public static void main(String[] args) {
launch();
}
}

For the specific example you posted, the easiest approach is to disable the button immediately prior to starting the animation, and enable it again when the animation stops. Here is one way to do this:
public class AnimationTest extends Application {
private final Label messageLabel = new Label();
#Override
public void start(Stage stage) {
VBox vBox = new VBox();
vBox.setAlignment(Pos.CENTER);
Scene scene = new Scene(vBox, 320, 240);
vBox.getChildren().add(messageLabel);
Button button = new Button();
button.setOnAction(event -> {
Animation animation = sendMessage("Some animated text.");
button.disableProperty().bind(Bindings.equal(animation.statusProperty(), Animation.Status.RUNNING));
});
vBox.getChildren().add(button);
stage.setScene(scene);
stage.show();
}
private Animation sendMessage(String message) {
final IntegerProperty i = new SimpleIntegerProperty(0);
Timeline timeline = new Timeline();
KeyFrame keyFrame = new KeyFrame(
Duration.millis(40),
event -> {
if (i.get() > message.length()) {
timeline.stop();
} else {
messageLabel.setText(message.substring(0, i.get()));
i.set(i.get() + 1);
}
});
timeline.getKeyFrames().add(keyFrame);
timeline.setCycleCount(Animation.INDEFINITE);
timeline.play();
return timeline ;
}
public static void main(String[] args) {
launch();
}
}
If you want to allow these messages to accumulate in a queue, and a new animation to start when the old one finishes, you need to keep a queue of the messages and a reference to a current animation that's running (if there is one). You can poll the queue from an AnimationTimer and start a new animation when a new message appears, if there is no current animation running.
I'd recommend thinking about whether this is the approach you want to take; there's no guarantee here that your messages will not appear more quickly than they can be animated, in which case the queue will grow indefinitely. However, this is an implementation if you can otherwise assure that this is not the case:
public class AnimationTest extends Application {
private final Label messageLabel = new Label();
private final Queue<String> messages = new LinkedList<>();
private Animation currentAnimation = null ;
#Override
public void start(Stage stage) {
VBox vBox = new VBox();
vBox.setAlignment(Pos.CENTER);
Scene scene = new Scene(vBox, 320, 240);
vBox.getChildren().add(messageLabel);
Button button = new Button();
button.setOnAction(event -> messages.add("Some animated text."));
AnimationTimer timer = new AnimationTimer() {
#Override
public void handle(long l) {
if (currentAnimation == null || currentAnimation.getStatus() == Animation.Status.STOPPED) {
String message = messages.poll();
if (message != null) {
currentAnimation = sendMessage(message);
currentAnimation.play();
}
}
}
};
timer.start();
vBox.getChildren().add(button);
stage.setScene(scene);
stage.show();
}
private Animation sendMessage(String message) {
final IntegerProperty i = new SimpleIntegerProperty(0);
Timeline timeline = new Timeline();
KeyFrame keyFrame = new KeyFrame(
Duration.millis(40),
event -> {
if (i.get() > message.length()) {
timeline.stop();
} else {
messageLabel.setText(message.substring(0, i.get()));
i.set(i.get() + 1);
}
});
timeline.getKeyFrames().add(keyFrame);
timeline.setCycleCount(Animation.INDEFINITE);
return timeline ;
}
public static void main(String[] args) {
launch();
}
}
Note there are no threading considerations here. The handle() method is invoked on the FX Application Thread, so the only requirement is that the messages are placed in the queue on the same thread. This happens in this example because the button's event handler is invoked on that thread. If your messages are coming from a background thread, you should ensure they are added to the queue on the FX Application Thread, either by using Platform.runLater(...) or (preferably) by using the JavaFX Concurrency API (i.e. by retrieving the messages in a Task or Service and adding them to the queue in an onSucceeded handler).

Set a boolean (best do it atomic, because multithreading and stuff...) at animation start & end.
Disable the Button when boolean is in animation phase.

Own minimize button with effect

#FXML
void minimize(MouseEvent event) {
Stage stage=(Stage) iconMinimize.getScene().getWindow();
stage.setIconified(true);
}
I have an icon that minimizes my program by mouse click. For example, when I minimize Windows for a program, you can see how the program works with an effect. The program slowly moves back to the taskbar. I would like to have such an effect too. If I do that with the code from the top, the program is right in the system tray. How do I get such an effect?

Animate the window size when you want to iconify the app and listen to the iconified property to do the reverse animation when the Stage is restored:
#Override
public void start(Stage primaryStage) {
StageHideAnimator.create(primaryStage);
Button minimize = new Button("minimize");
minimize.setOnAction(evt -> {
StageHideAnimator animator = StageHideAnimator.getStageHideAnimator((Node) evt.getSource());
animator.iconify();
});
Button close = new Button("close");
close.setOnAction(evt -> primaryStage.close());
VBox content = new VBox(minimize, close, new Rectangle(200, 200, Color.BLUE));
content.setPadding(new Insets(10));
content.setStyle("-fx-background-color: green;");
primaryStage.initStyle(StageStyle.TRANSPARENT);
Scene scene = new Scene(content);
primaryStage.setScene(scene);
primaryStage.setOnShown(evt -> {
WindowUtils.placeAtPrimaryScreenBottom(primaryStage);
});
primaryStage.show();
}
public final class WindowUtils {
private WindowUtils() { }
public static void placeAtPrimaryScreenBottom(Stage stage) {
stage.setY(Screen.getPrimary().getVisualBounds().getMaxY() - stage.getHeight());
}
}
public class StageHideAnimator {
// key used for storing animators in the properties map of a Stage
private static final Object PROPERTY_KEY = new Object();
private double sceneHeight;
private double decorationHeight;
private final Stage stage;
private Timeline animation;
// fraction of height relative to full height
private final DoubleProperty height = new SimpleDoubleProperty();
// getter for the animator
public static StageHideAnimator getStageHideAnimator(Stage stage) {
return (StageHideAnimator) stage.getProperties().get(PROPERTY_KEY);
}
// get animator of window containing the node
public static StageHideAnimator getStageHideAnimator(Node node) {
return getStageHideAnimator((Stage) node.getScene().getWindow());
}
private StageHideAnimator(Stage stage) {
this.stage = stage;
stage.iconifiedProperty().addListener((o, oldValue, newValue) -> {
// do reverse hide animation when stage is shown
if (!newValue) {
animation.setRate(-1);
if (animation.getStatus() == Animation.Status.STOPPED) {
animation.playFrom("end");
} else {
animation.play();
}
}
});
height.addListener((o, oldValue, newValue) -> {
// resize stage and put it at the bottom of the primary screen
stage.setHeight(sceneHeight * newValue.doubleValue() + decorationHeight);
WindowUtils.placeAtPrimaryScreenBottom(stage);
});
}
public static StageHideAnimator create(Stage stage) {
if (stage.getProperties().containsKey(PROPERTY_KEY)) {
// don't allow 2 animators
throw new IllegalArgumentException("animator already exists");
}
StageHideAnimator animator = new StageHideAnimator(stage);
stage.getProperties().put(PROPERTY_KEY, animator);
return animator;
}
private void initHeight() {
sceneHeight = stage.getScene().getHeight();
decorationHeight = stage.getHeight() - sceneHeight;
}
public void iconify() {
if (stage.isIconified()) {
return;
}
if (animation == null) {
initHeight(); // save initial height of stage
animation = new Timeline(
new KeyFrame(Duration.ZERO, new KeyValue(height, 1d, Interpolator.EASE_BOTH)),
new KeyFrame(Duration.seconds(1), new KeyValue(height, 0d, Interpolator.EASE_BOTH)));
animation.setOnFinished(evt -> {
if (animation.getRate() == 1) {
// iconify at end of hiding animation
animation.setRate(-1);
stage.setIconified(true);
}
});
animation.play();
} else {
animation.setRate(1);
if (animation.getStatus() == Animation.Status.STOPPED) {
initHeight(); // save initial height of stage
animation.playFromStart();
} else {
animation.play();
}
}
}
}

Loading JavaFX GUI in background

I'm currently trying to create a Splash Screen for my program since it takes some time to start up.
The problem is that it takes a while to create the GUI (creating dialogues, updating tables etc.). And I can't move the GUI creation to a background thread (like the "Task" class), since I'll get an "Not on FXApplication Thread" exception.
I tried using:
Platform.runLater(new Runnable() {
public void run() {
//create GUI
}
}
And the "call" method of a Task:
public class InitWorker extends Task<Void> {
private Model model;
private ViewJFX view;
public InitWorker(Model model) {
this.model = model;
}
#Override
protected Void call() throws Exception {
View view = new View();
Collection collection = new Collection();
//do stuff
}
}
When I wrote the program in Swing I could just display and update the Splash Screen on the EventDispatchThread, without any real concurreny. The code looked like this:
public void build() {
MainOld.updateProgressBar(MainOld.PROGRESSBAR_VALUE++, "Creating Menus");
menuCreator = new MenuCreatorOld (model, this);
menuCreator.createMenu();
MainOld.updateProgressBar(MainOld.PROGRESSBAR_VALUE, "Creating Toolbar");
toolBar = menuCreator.createToolBar();
createWesternPanelToolBar();
shoppingPanel = new ShoppingListOld(model, this, collectionController, shoppingController, controller);
centerTabbedPane = new JTabbedPane();
MainOld.updateProgressBar(MainOld.PROGRESSBAR_VALUE++, "Creating Collection");
collectionPanel = new CollectionOld(model, collectionController, this, controller);
MainOld.updateProgressBar(MainOld.PROGRESSBAR_VALUE++, "Creating Wish List");
wishPanel = new WishListOld(model, this, collectionController, wishController, controller);
MainOld.updateProgressBar(MainOld.PROGRESSBAR_VALUE++, "Creating Folders Table");
//and so on
}
public static void updateProgressBar(int progressValue, String text) {
System.out.println("Loading Bar Value:"+progressValue);
progressBar.setValue(progressValue);
loadingLabel.setText(text);
progressBar.setString(text);
}
Is there any way to create the GUI in the background while displaying a Splash Screen with a loading bar?
Edit:
I had a look at my code and was able to decrease the startup time by 5 seconds. Most of the dialogs pull data from the database when they are created. So I moved the creation of the dialogs into their getter methods. That resulted in an improvement of 3 seconds. But I would still like to know if there is in a way to create the GUI on a background thread.
Edit:
As suggested, I also tried using "RunLater" in a "Task".
This way I can create the GUI and display the SplashScreen, but I can't update the progress bar and progress label, since the GUI creation blocks the JavaFX application thread. The progress bar and label are only updated, after the GUI has been fully created.
Here's an example you guys can run (I removed the splash screen and only kept the progress bar and progress label):
public class InitWorker extends Task<Void> {
private static ProgressBar progressBar;
private static Label progressLabel;
private static double PROGRESS_MAX = 5;
private double loadingValue;
public InitWorker() {
loadingValue = 0;
}
#Override
protected void succeeded() {
System.out.println("Succeeded");
}
#Override
protected void failed() {
System.out.println("Failed");
}
#Override
protected Void call() throws Exception {
System.out.println("RUNNING");
Platform.runLater(new Runnable() {
public void run() {
displaySplashScreen();
for(int i=0; i<10; i++) {
try {
Thread.sleep(200);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
updateProgressBar(loadingValue++, "Label "+i);
Stage stage = new Stage();
Label label = new Label("Label " + i);
VBox panel = new VBox();
panel.getChildren().add(label);
Scene scene = new Scene(panel);
stage.setScene(scene);
stage.centerOnScreen();
stage.show();
}
// updateProgressBar(1, "Initializing...");
}});
return null;
}
public void updateProgressBar(double loadingValue, String text) {
progressBar.setProgress(loadingValue / PROGRESS_MAX);
progressLabel.setText(text);
}
public static void displaySplashScreen() {
Stage progressBarStage = new Stage();
progressBar = new ProgressBar();
Scene progressBarScene = new Scene(progressBar);
progressBarStage.setScene(progressBarScene);
Stage progressLabelStage = new Stage();
progressLabel = new Label("Loading...");
progressLabel.setPadding(new Insets(5));
progressLabel.setStyle("-fx-background-color: red");
Scene progressLabelScene = new Scene(progressLabel);
progressLabelStage.setScene(progressLabelScene);
double progressBarWidth = 500;
double progressBarHeight = 75;
//muss angezeigt werden, um sie abhängig von Größe zu positionieren
progressBarStage.show();
progressLabelStage.show();
//
progressBarStage.setWidth(progressBarWidth);
progressBarStage.setHeight(progressBarHeight);
progressBarStage.centerOnScreen();
progressBarStage.centerOnScreen();
progressLabelStage.setY(progressLabelStage.getY() + 25);
}
}

See Task documentation titled "A Task Which Modifies The Scene Graph", which provides an example:
final Group group = new Group();
Task<Void> task = new Task<Void>() {
#Override protected Void call() throws Exception {
for (int i=0; i<100; i++) {
if (isCancelled()) break;
final Rectangle r = new Rectangle(10, 10);
r.setX(10 * i);
Platform.runLater(new Runnable() {
#Override public void run() {
group.getChildren().add(r);
}
});
}
return null;
}
};
The above example add the rectangles to the scene graph via a 100 runLater calls. A more efficient way to do this would be to add the rectangles to a group not attached to the active scene graph, then only add the group to the active scene graph in the runLater call. For example:
final Group groupInSceneGraph = new Group();
Task<Void> task = new Task<Void>() {
#Override protected Void call() throws Exception {
final Group localGroup = new Group();
for (int i=0; i<100; i++) {
if (isCancelled()) break;
final Rectangle r = new Rectangle(10, 10);
r.setX(10 * i);
localGroup.getChildren().add(r);
}
Platform.runLater(new Runnable() {
#Override public void run() {
groupInSceneGraph.add(localGroup);
}
});
return null;
}
};
You can create and modify most scene graph objects off of the JavaFX application thread (including loading FXML), as long as the objects aren't attached to the active scene graph. By active scene graph I mean a scene graph which is currently attached as a scene to a displayed stage. (A complicated control such as a WebView may be an exception to this rule and may require creation on the JavaFX application thread).
You must only attach the scene graph objects created off of the JavaFX application thread to the active scene graph on the JavaFX application thread (for example using Platform.runLater()). And, you must work with them on the JavaFX application thread as long they continue to be attached to the active scene graph.

Animations in JavaFX using RxJava without blocking GUI

This is a simple class that uses bubble sort to sort a List of Integers and push the result of every iteration to a Subject from RxJava library, with some delay.
public class Sorter {
private PublishSubject<List<Integer>> subject = PublishSubject.create();
public void bubbleSort(int delay) throws InterruptedException {
List<Integer> ints = randomIntegers(0,200,10);
for (int i = 0; i < ints.size(); i++) {
for (int j = 0; j < ints.size() - 1; j++) {
if (ints.get(j) > ints.get(j + 1)) {
Collections.swap(ints, j, j + 1);
subject.onNext(ints);
Thread.sleep(delay);
}
}
}
}
private List<Integer> randomIntegers(int origin, int bound, int limit) {
return new Random()
.ints(origin, bound)
.limit(limit)
.boxed()
.collect(Collectors.toList());
}
public PublishSubject<List<Integer>> getSubject() {
return subject;
}
}
I can observe the result very easily with a sample code:
int delay = 100;
Sorter sorter = new Sorter();
PublishSubject<List<Integer>> subject = sorter.getSubject();
subject.subscribe(System.out::println);
sorter.bubbleSort(delay);
I want, however, to see the results of the iterations as moving rectangles of different height representing the numbers. I use JavaFX. After every iteration, I want to clear the application window and redraw everything.
public class Main extends Application {
private Group root;
#Override
public void start(Stage primaryStage) throws InterruptedException {
root = new Group();
Scene scene = new Scene(root, 500, 500, Color.WHITE);
primaryStage.show();
primaryStage.setScene(scene);
Sorter sorter = new Sorter();
PublishSubject<List<Integer>> subject = sorter.getSubject();
subject.subscribe(this::drawRectangles);
sorter.bubbleSort(100);
}
private void drawRectangles(List<Integer> integers) {
root.getChildren().clear();
rectangles.clear();
for (int i = 0; i<integers.size(); i++) {
Rectangle rectangle = new Rectangle(i * 20, 500 - integers.get(i), 10, integers.get(i));
rectangle.setFill(Color.BLACK);
rectangles.add(rectangle);
}
root.getChildren().addAll(rectangles);
}
public static void main(String[] args) {
launch(args);
}
}
However, I only see the last iteration's result. Prior to that, I can only see that the application is running and the GUI thread is blocked.
How can I make the background RxJava calculations non-blocking to my GUI?
EDIT: I solved the issue by running the computation code in another thread, like so:
#Override
public void start(Stage primaryStage) throws InterruptedException {
new Thread(() -> {
Sorter sorter = new Sorter();
sorter.getSubject().subscribe(this::drawRectangles);
try {
sorter.bubbleSort(100);
} catch (InterruptedException e) {
e.printStackTrace();
}
}).start();
root = new Group();
Scene scene = new Scene(root, 1500, 500, Color.WHITE);
primaryStage.show();
primaryStage.setScene(scene);
}
And wrapper the drawRectangles in Platform.runLater(() -> {} expression.
This seems to be working, although I feel like there might me a possibility to run this with observeOn somehow.

Use RxJavaFX scheduler your UI tasks.
You need do the sort task sorter.bubbleSort in another thread instead of UI thread. And
observeOn(JavaFxScheduler.getInstance())
to schedule UI task back into UI thread.
Only change your start method to:
#Override
public void start(Stage primaryStage) throws InterruptedException {
root = new Group();
Scene scene = new Scene(root, 500, 500, Color.WHITE);
primaryStage.show();
primaryStage.setScene(scene);
Sorter sorter = new Sorter();
sorter.getSubject()
.observeOn(JavaFxScheduler.platform())
.subscribe(this::drawRectangles);
new Thread(() -> uncheck(() -> sorter.bubbleSort(100))).start();
}

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